[Federal Register Volume 64, Number 137 (Monday, July 19, 1999)]
[Notices]
[Pages 38706-38740]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-17774]



[[Page 38705]]

_______________________________________________________________________

Part II





Environmental Protection Agency





_______________________________________________________________________



National Air Toxics Program: The Integrated Urban Strategy; Notice

  Federal Register / Vol. 64, No. 137 / Monday, July 19, 1999 / 
Notices  

[[Page 38706]]



ENVIRONMENTAL PROTECTION AGENCY

[FRL-6376-7; Docket No. A-97-44]


National Air Toxics Program: The Integrated Urban Strategy

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice.

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SUMMARY: This document provides an overview of EPA's national effort to 
reduce air toxics, including stationary and mobile source standards, 
cumulative risk initiatives, assessment approaches, and education and 
outreach. This national air toxics program includes activities under 
multiple Clean Air Act (Act) authorities to reduce air toxics emissions 
from all sources, including major industrial sources, smaller 
stationary sources, and mobile sources such as cars and trucks. By 
integrating activities under different parts of the Act, EPA can better 
address cumulative public health risks and adverse environmental 
impacts posed by exposures to multiple air toxics in areas where the 
emissions and risks are most significant.
    In addition, this document describes a new major component of our 
national effort, the Integrated Urban Air Toxics Strategy (Strategy) 
developed under the authority of sections 112(k) and 112(c)(3) of the 
Act. The Strategy reflects the public comments received on the draft 
Strategy, which was published on September 14, 1998 (63 FR 49240).
    The Strategy includes a description of risk reduction goals; a list 
of 33 hazardous air pollutants (HAPs) judged to pose the greatest 
potential threat to public health in the largest number of urban areas, 
including 30 HAPs specifically identified as being emitted from smaller 
industrial sources known as ``area'' sources; and a list of area source 
categories which emit a substantial portion of these HAPs, and which 
are being considered for regulation under section 112(d). Because 
mobile sources are an important contributor to the urban air toxics 
problem, the Strategy also describes actions under Title II (including 
section 202(l)) of the Act to reduce toxics from these sources, 
including those which address diesel particulate matter (PM).
    The Strategy by itself doesn't automatically result in regulation 
or control of emissions. The EPA will perform further analyses of HAP 
emissions, control methods, and health impacts, as appropriate, for 
stationary and mobile sources. These analyses will inform any ultimate 
regulatory requirements that EPA develops under the Strategy.

ADDRESSES: A docket containing information relating to the development 
of this notice (Docket No. A-97-44) is available for public inspection 
and copying between 8:00 a.m. and 5:30 p.m., Monday through Friday 
except for Federal holidays, in the Air and Radiation Docket and 
Information Center (MC-6102), Room M-1500, U.S. Environmental 
Protection Agency, 401 M Street, SW, Washington, DC 20460; telephone 
(202) 260-7548. The docket office may charge a reasonable fee for 
copying.

FOR FURTHER INFORMATION CONTACT: Laura McKelvey, Office of Air Quality 
Planning and Standards (MD-13), U.S. Environmental Protection Agency, 
Research Triangle Park, North Carolina, 27711, telephone number (919) 
541-5497, electronic mail address: McKelvey.Laura''epa.gov.

SUPPLEMENTARY INFORMATION:

Plain Language

    In compliance with President Clinton's June 1, 1998 Executive 
Memorandum on Plain Language in Government Writing, this package is 
written using plain language. Thus, the use of ``we'' in this package 
refers to EPA. The use of ``you'' refers to the reader and may include 
State, local or Tribal government agencies, industry, environmental 
groups, or other interested individuals.

Executive Order 12866

    Under Executive Order 12866 (58 FR 51735, October 4,1993), the 
Agency must determine whether a regulatory action is ``significant'' 
and therefore subject to Office of Management and Budget (OMB) review 
and the requirements of the Executive Order. The Order defines 
``significant'' regulatory action as one that is likely to lead to a 
rule that may either: (1) have an annual effect on this economy of $100 
million or more, or adversely and materially affect a sector of the 
economy, productivity, competition, jobs, the environment, public 
health or safety, or State, local or Tribal governments or communities; 
(2) create a serious inconsistency or otherwise interfere with an 
action taken or planned by another Agency; (3) materially alter the 
budgetary impact of entitlement, grants, user fees, or loan programs or 
the rights and obligations of recipients thereof; or (4) raise novel 
legal or policy issues arising out of legal mandates, the President's 
priorities, or the principles set forth in the Executive Order.
    This notice was submitted to OMB for review. Any written comments 
from OMB and written EPA responses are available in the docket.

Docket

    The docket is an organized file containing information related to 
the development of the Strategy. The main purpose of this docket is to 
allow you to readily identify and locate documents relevant to the 
development of the Strategy. The docket is available for public 
inspection at the EPA's Air and Radiation Docket and Information 
Center, which is listed in the ADDRESSES section of this document.

Electronic Access and Filing Addresses

    You can get this notice and other background information in Docket 
No. A-97-44 by contacting our Air and Radiation Docket and Information 
Center (see ADDRESSES), or by visiting our website at ``http://
www.epa.gov/ttn/uatw/urban/urbanpg.html'' for electronic versions of 
the notice and other information. For assistance in downloading files, 
call the TTN HELP line at (919) 541-5384.

Outline

    The information in this document is organized as follows:

I. National Efforts to Reduce Air Toxics
    A. What is our overall air toxics program?
    B. Why are we concerned about urban air in particular?
    C. What is the Integrated Urban Air Toxics Strategy?
II. Federal Activities Related to the Integrated Urban Air Toxics 
Strategy
    A. What HAPs pose the greatest threat in urban areas?
    B. How does EPA plan to address requirements for area sources of 
HAPs?
    C. What regulatory actions will EPA take to implement the 
Strategy?
    D. How do the various Federal authorities help EPA implement the 
Strategy?
III. State, Local and Tribal Activities
    A. Why are State, local and Tribal programs integral to the 
process?
    B. What are the objectives of State, local and Tribal 
activities?
    C. What were comments on the State/local/Tribal programs and how 
are they being addressed in the Strategy development?
    D. How can State, local or Tribal agencies participate in the 
Strategy?
    E. What elements should a State, local or Tribal program 
contain?
IV. Assessment Activities
    A. How will we assess progress toward goals?
    B. What methods, tools, and data will we use to estimate risk?
    C. What is our overall risk assessment approach for the 
Strategy?
    D. How will we design future assessments?
V. Knowledge and Tools

[[Page 38707]]

    A. How will we review and expand ambient monitoring networks?
    B. How will we update and maintain the emission inventory?
    C. What air quality and exposure models will we use to implement 
the Strategy?
    D. What are the research needs and what is EPA doing to address 
them?
VI. Public Participation and Communication
    A. How will we encourage stakeholder involvement?
    B. What is our overall timeline for action?
    C. What reports will we prepare to communicate with the public?

Appendix A. Summary of other authorities, laws, rules, and programs 
to help reduce HAP emissions

I. National Efforts to Reduce Air Toxics

    The 1990 Clean Air Act Amendments provided the foundation for our 
current air toxics program. This program is designed to characterize, 
prioritize and equitably address the serious impacts of HAPs on the 
public health and the environment through a strategic combination of 
regulatory approaches, voluntary partnerships, ongoing research and 
assessments, and education and outreach. Since 1990, we've made 
considerable progress in reducing emissions of air toxics \1\ through 
regulatory, voluntary and other programs. To date, our overall air 
toxics program, summarized in section I.A., has focused on reducing 
emissions of toxic air pollutants from major stationary sources through 
the implementation of technology-based emissions standards as required 
in section 112(d). These actions have resulted, or are projected to 
result, in substantial reductions in HAP emissions.\2\ Additionally, 
actions to address mobile and stationary sources under other Clean Air 
Act programs are achieving reductions in HAP emissions (for example, 
the phase-out of lead from gasoline). However, we expect that the 
emission reductions that will result from these other actions are only 
part of what will be necessary to protect public health and the 
environment from toxic air pollutants. In identifying additional steps, 
we'll use a risk-based focus to develop, implement and facilitate 
additional Federal and local regulatory and voluntary measures.
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    \1\ Our use of the terms ``air toxics'' or ``toxic air 
pollutants'' in this notice refers specifically to those pollutants 
which are listed under section 112(b) of the Act as ``hazardous air 
pollutants'' or HAPs. There are currently 188 HAPs listed.
    \2\ We project that by 2002, the full implementation of section 
112(d) maximum achievable control technology (MACT) standards 
adopted to date will yield emissions reductions of approximately one 
million tons of HAPs per year. Within the next six years, completion 
and full implementation of section 112(d) technology-based standards 
for the remaining stationary source categories listed pursuant to 
section 112(c) will contribute additional emissions reductions.
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    In considering additional steps towards protecting human health and 
the environment, we need to identify and focus on issues of highest 
priority. Current information indicates that there are potentially 
significant health risks associated with air toxics exposures affecting 
large numbers of people in urban areas, as discussed in section I.B. 
Recognizing this, Congress instructed us to develop a strategy for air 
toxics in urban areas that includes specific actions to address the 
large number of smaller, area sources,\3\ and that contains broader 
risk reduction goals encompassing all stationary sources. More 
specifically, section 112(k)(1) states:

    \3\ Area sources are those stationary sources that emit, or have 
the potential to emit, less than 10 tons per year of any one HAP or 
less than 25 tons per year of a combination of HAPs. Examples 
include hospital sterilizers and small publicly owned treatment 
works.
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    The Congress finds that emissions of hazardous air pollutants 
from area sources may individually, or in the aggregate, present 
significant risks to the public health in urban areas. Considering 
the large number of persons exposed and the risks of carcinogenic 
and other adverse health effects from hazardous air pollutants, 
ambient concentrations characteristic of large urban areas should be 
reduced to levels substantially below those currently experienced.

    As the ambient concentrations of HAPs in urban areas result from a 
combination of different sources (e.g., area, major,\4\ and mobile \5\) 
emitting many of the same pollutants, we need to recognize 
contributions from all types of sources in achieving the reductions in 
ambient concentrations referred to in this subsection. Therefore, in 
addition to addressing specific statutory requirements for area 
sources, we've devised an integrated strategy for reducing cumulative 
public health risks in urban areas posed by the aggregated exposures to 
air toxics from all sources. The Integrated Urban Air Toxics Strategy 
(the Strategy) presented here, and summarized in section I.C. below, is 
one part of our overall national effort to reduce toxics. The basic 
components of the Strategy consist of the same basic elements as those 
of the overall air toxics program but with a specific focus on the 
particular needs of urban areas.
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    \4\ Major stationary sources are sources that emit, or have the 
potential to emit, more than 10 tons per year of any one HAP or 25 
tons per year of a combination of HAPs. Examples include chemical 
plants, oil refineries, aerospace manufacturers and steel mills.
    \5\ Mobile sources include motor vehicles (e.g., cars and 
trucks) and off-road equipment (e.g., construction equipment and 
lawn mowers), and their fuels.
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    Before we describe the national efforts to control air toxics in 
more detail, we want to provide a brief overview of what air toxics 
are, their health and environmental effects, and their sources. These 
topics are discussed in more detail later in the notice, but their 
introduction here will help ensure that the remaining discussion in 
section I is based on a common understanding of the nature of the air 
toxics problem.
     What are air toxics?
    The Act identifies 188 compounds as HAPs. They include pollutants 
like benzene found in gasoline, perchloroethylene emitted from dry 
cleaners, methylene chloride used as an industrial solvent, heavy 
metals like mercury and lead, polychlorinated biphenyls (PCBs), dioxins 
and some pesticides. These pollutants may cause cancer or other serious 
effects in humans or in the environment. Health concerns result from 
both short-and long-term exposures to these pollutants. They may 
disperse locally, regionally, nationally, or globally and after 
deposition may persist in the environment and/or bioaccumulate in the 
food chain, depending on their characteristics (such as vapor 
pressures, atmospheric transformation rates). Although not specifically 
listed as a HAP in section 112(b) of the Act, diesel emissions contain 
many HAPs, and are thus collectively considered under our overall 
program and the Strategy.
     What health and environmental effects do they cause?
    Hazardous air pollutants can cause many health effects. More than 
half are known or suspected to be human carcinogens. Many are known to 
have respiratory, neurological, immune or reproductive effects, 
particularly for more susceptible or sensitive populations, such as 
children. Many of the HAPs are known to also cause adverse effects in 
many fish and animal species, including toxicity in fish or causing 
reproductive decline in bird species, including endangered species. 
These environmental effects may be felt by individual species within a 
single level of the food chain or by the entire ecosystem where 
multiple species are affected.
     What are the sources of air toxics?
    There are literally millions of sources of air toxics, including 
large industrial complexes like chemical plants, oil refineries and 
steel mills; small (area) sources such as dry cleaners, gas stations, 
and small manufacturers; and mobile sources including cars, trucks, 
buses, and nonroad vehicles like ships and farm equipment.

[[Page 38708]]

A. What is Our Overall Air Toxics Program?

    Our overall approach to reducing air toxics reflects the mandates 
under the Act to develop technology-based standards and then 
subsequently to implement a risk-based program to ensure the protection 
of public health and the environment. For example, in amending the Act 
in 1990, Congress required us to establish national standards to reduce 
emissions of air toxics from stationary and mobile sources. Under 
section 112(d), Congress emphasized the implementation of technology-
based standards for stationary source categories emitting air toxics. 
These emission standards are known as maximum achievable control 
technology (MACT) standards, and generally available control technology 
(GACT) standards. Section 112(k) requires us to list area source 
categories and to ensure 90 percent of the emissions from area sources 
are subject to standards pursuant to section 112(d). In addition, under 
section 202, Congress requires us to set standards to control HAPs from 
motor vehicles and their fuels.
    Further, the Act contains additional provisions that have a risk-
based focus. Section 112(f) of the Act requires us to evaluate the risk 
remaining after implementation of MACT standards (i.e., the ``residual 
risk'') in order to evaluate the need for additional stationary source 
standards to protect public health and the environment.
    Under section 112(k), the Act specifically mandated that we develop 
a Strategy (the subject of this notice) to address public health risks 
posed by air toxics from area sources in urban areas and report to 
Congress on this issue. In addition, section 112(k) of the Act also 
mandates that the Strategy achieve a 75-percent reduction in cancer 
incidence attributable to HAPs emitted by stationary sources.
    Other sections of the Act call for study of other types of specific 
air toxics problems including a focus on certain HAPs that persist and 
bioaccumulate in the environment. These studies include the deposition 
of air toxics to Great Waters,\6\ HAP emissions from electric 
utilities, and the health and environmental effects of mercury 
emissions, in particular.\7\
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    \6\ The Great Lakes, Chesapeake Bay, Lake Champlain and coastal 
waters are collectively referred to as the ``Great Waters.''
    \7\ These studies are required by sections 112(m), 112(n)(1)(A), 
and 112(n)(1)(B), respectively.
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    Our current national air toxics goal was developed to meet 
requirements of the Government Performance and Results Act (GPRA), 
which requires us to report on the status of our progress in 
implementing our programs. That goal is to reduce air toxics emissions 
by 75 percent from 1993 levels and to significantly reduce the risk to 
the public of cancer and other serious adverse health effects caused by 
airborne toxics. Because our knowledge and tools to assess the impacts 
of these emissions on public health and the environment were limited 
when we set this current goal, it reflects the straightforward intent 
to reduce total air toxics emissions as a means to reduce risks 
associated with exposure to air toxics. However, as we extend our 
knowledge, develop better assessment tools and begin to address the 
risks associated with these emissions as required by the Clean Air Act, 
we intend to modify our goal to one directed specifically at risk 
reductions associated with exposure to air toxics. In working toward 
such a risk-based goal, we'll focus particularly on populations and 
areas disproportionately impacted, including, for example, densely 
populated areas, children at risk of developmental effects and people 
who are highly exposed to water and food affected by air toxics (e.g., 
subsistence fishers living near contaminated water bodies). For more 
information on assessments, see section IV for an explanation of the 
assessment methods.
    We intend to progress toward the program goal through a combination 
of our authorities, regulatory activities and voluntary initiatives. 
The overall approach to reducing air toxics consists of the following 
four key components:
     Source-specific standards and sector-based standards. As 
previously mentioned, section 112 specifies MACT/GACT standards, and 
residual risk standards, as well as those area source standards which 
are contemplated by the Integrated Urban Air Toxics Strategy. 
Additionally, section 129 requires standards for solid waste 
incineration and section 202(l) requires EPA, based on the mobile-
source related Air Toxics Study, to promulgate reasonable requirements 
to control HAPs from motor vehicles and their fuels.
     National, regional, and community-based initiatives to 
focus on multi-media and cumulative risks. Section 112(k)(4) requires 
us to ``encourage and support area wide strategies developed by the 
State or local air pollution control agencies.'' Our risk initiatives 
will include State, local and Tribal program activities consistent with 
the Integrated Urban Air Toxics Strategy on the local level as well as 
Federal and regional activities associated with the multimedia aspects 
of HAPs, such as the Great Waters program \8\ and initiatives 
concerning mercury, and other persistent bioaccumulative toxics (PBTs). 
Other Agency initiatives include collaboration between the air and 
water programs on the impact of air deposition on water quality (e.g., 
by accounting for the contribution of air deposition to the total 
maximum daily load (TMDL) of pollutants to a water body), and 
collaboration between offices within EPA's air program to assess the 
risks from exposures to air toxics indoors and to develop non-
regulatory, voluntary programs to address those risks.
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    \8\ Under section 112(m) of the Act, we assess and report to 
Congress on the deposition of air pollutants in the Great Lakes, 
Chesapeake Bay, Lake Champlain, and coastal waters. The third report 
to Congress on ``The Deposition of Air Pollutants to the Great 
Waters'' will be released later this year.
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     National air toxics assessments (NATA). National air 
toxics assessments will help us identify areas of concern, characterize 
risks, and track our progress toward meeting our overall air toxics 
program goals, as well as the risk-based goals of the various 
activities and initiatives within the program, such as the Integrated 
Urban Air Toxics Strategy. The NATA activities include expansion of air 
toxics monitoring, improving and periodically updating emissions 
inventories, national- and local-scale air quality, multi-media and 
exposure modeling (including modeling which considers stationary and 
mobile sources), continued research on health effects and exposures to 
both ambient and indoor air, and use and improvement of exposure and 
assessment tools. These activities will provide us with improved 
characterizations of air toxics risk and risk reductions resulting from 
emissions control standards and initiatives for both stationary and 
mobile source programs.
     Education and outreach. In light of the scientific 
complexity inherent in air toxics issues, we recognize that the success 
of our overall air toxics program depends in part on our ability to 
communicate effectively with the public about air toxics risks and 
activities necessary to reduce those risks. This includes education and 
outreach efforts on air toxics in the ambient as well as indoor 
environments.
    Following is a more detailed discussion of the activities under 
each of the four components of the national program.

[[Page 38709]]

1. Source-specific Standards and Sector-based Standards
    Maximum achievable control technology. The 1990 Clean Air Act 
Amendments required us to use a ``technology-based'' and a performance-
based approach to significantly reduce emissions of air toxics from 
major sources of air pollution. These reductions are to be followed by 
a risk-based approach to address any remaining, or residual risks. 
Under the ``technology-based'' approach we develop standards for 
controlling the ``routine'' emissions of air toxics from each major 
source within an industry group (or ``source category''). These 
standards--known as ``maximum achievable control technology (MACT) 
standards''--are based on emissions levels that are already being 
achieved by the better controlled sources in an industry. This approach 
assures citizens nationwide that each major source of HAPs will be 
required to employ effective measures to limit its emissions.
    Under this program, we listed for regulation 174 source categories 
that emit the 188 HAPs listed under section 112(b). To date, we've 
promulgated 43 standards regulating 78 source categories. We've 
proposed an additional 7 standards covering 8 source categories. Five 
source categories have been delisted. We're continuing to develop 
standards to cover the remaining source categories.
    Combustion standards. We've also issued final rules to control 
emissions of certain air toxics from certain types of solid waste 
combustion facilities. These rules, required under section 129 of the 
Act, set emission limits for new solid waste combustion facilities and 
provide emissions guidelines for existing solid waste combustion 
facilities. These rules affect municipal waste combustors and hospital/
medical/infectious waste incinerators, which account for 30 percent of 
the national mercury emissions to the air. By the time these rules are 
fully implemented we expect them to reduce mercury emissions from these 
sources by about 90 percent from current levels, and reduce dioxin/
furan emissions by more than 95 percent from current levels. We're 
working on additional rules to address industrial and commercial waste 
incinerators, other solid waste incinerators and small municipal waste 
combustor units.
    Residual risk. The residual risk program, required under section 
112(f) of the Act, is designed to assess the risk from source 
categories after MACT standards are implemented. If we find a 
remaining, or residual, risk, we're required, within 8 years of the 
promulgation of the MACT standard, to set additional standards if the 
level of residual risk doesn't provide an ``ample margin of safety to 
protect public health'' or ``to prevent, taking into consideration 
costs, energy, safety, and other relevant factors, an adverse 
environmental effect.'' \9\
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    \9\ The Residual Risk Report to Congress, March 3, 1999, 
describes our approach on risk assessment methods for use across the 
air toxics program, and our approach for conducting residual risk 
analyses. (EPA-453-/R-99-001)
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    In analyzing residual risk, we'll conduct risk assessments 
consistent with the Agency's human health and ecosystem risk assessment 
technical guidance and policies. We'll use a tiered approach, usually 
first conducting a screening level assessment for a source category, 
and move to a refined assessment only where the risks identified in the 
screening assessment appear unacceptable. Depending on the 
characteristics of the HAPs, these assessments will address single or 
multiple pathways of exposure as well as human and ecological 
endpoints.
    Risk management decisions will be consistent with Agency policies. 
For carcinogens, we'll use a linear dose-response model unless data 
support nonlinear mechanisms. We'll follow the Agency's mixtures 
guidelines where a source category emits multiple HAPs.
    For non-cancer effects, we'll use the EPA reference concentration 
or comparable criteria from other government agencies. As with the 
cancer effects, we'll follow the mixtures guidelines for emissions of 
multiple non-carcinogens.
    In general, we'll base decisions on exposures predicted from 
modeling HAP emissions in air and, where appropriate, other media. 
Where available, we'll include monitoring data as part of our analysis 
for refined assessments. We'll estimate the size and characteristics of 
the exposed population, and conduct uncertainty and variability 
analysis where appropriate.
    Currently we're conducting analyses on 13 of the earliest standards 
that we promulgated. We're conducting these analyses on a source 
category basis. Depending on the outcome of these analyses, we may find 
it necessary to modify our residual risk approach.
    Mobile source standards. We started enforcing the first federal 
emission standards for passenger cars in 1968. Since then, acting under 
specific mandates from the Congress and under general authority, we've 
developed emission standards for all types of highway vehicles, their 
fuels, and engines used in virtually all varieties of mobile or 
portable nonroad equipment such as tractors, construction vehicles, 
recreational and commercial vessels, and lawn and garden equipment. 
We've also made the emission standards more stringent over time. New 
highway vehicles using gasoline are now all equipped with advanced 
catalysts and computer-controlled fuel systems. Diesel vehicles and 
most nonroad engines have been substantially redesigned to meet our 
emission standards as well. Diesel buses in urban areas are subject to 
a special limit on their emissions of particulate matter. All gasoline 
and highway diesel fuel used in the United States is subject to 
emission-reducing standards for volatility and sulfur, respectively. 
About one-quarter of the gasoline used in the United States is now 
subject to our reformulated gasoline program, and has lower volatility, 
reduced concentrations of benzene and other aromatics, and other 
beneficial changes. In May of this year, we proposed stringent new 
standards for all cars and light trucks, and the gasoline they use. At 
the same time we issued an advanced notice of proposed rulemaking to 
solicit information relating to control of diesel fuel quality. This 
year, we're also reviewing our standards for heavy-duty highway 
vehicles. In 2001, we'll do the same for heavy-duty nonroad engines.
    To date, most of our emission standards have been aimed at 
improving urban air quality for the criteria pollutants carbon 
monoxide, ozone, and PM10. However, the emission control equipment on 
engines and vehicles, along with the fuel changes that have been needed 
to meet our emission standards, are also effective at reducing 
emissions of many HAPs. Our requirement to reduce and then end the use 
of lead additives in gasoline is an example of a standard that 
specifically reduced emissions of toxic pollutants. The reformulated 
gasoline program is another example, as it includes a performance 
standard for the emissions of several important HAPs.
    Because of the time it takes for older vehicles to retire and be 
replaced with newer vehicles that comply with the latest emission 
standards, total mobile source toxics emissions will decline for many 
years into the future.
    While the toxic reductions from our emission standards have been 
large, prior to 1990 we had no specific directions from Congress for a 
planned program to control toxic emissions from mobile sources. 
However, section 202(l), added by the Clean Air Act Amendments of 1990, 
requires us to complete a study of motor vehicle-related air toxics, 
and to promulgate

[[Page 38710]]

requirements for the control of HAPs from motor vehicles based on that 
study. We completed the required study in 1993, and are presently 
preparing an update to that study, and considering rulemaking under 
section 202(l)(2). In addition, the 1990 Amendments give us 
discretionary authority to control toxic emissions from nonroad mobile 
engines. We plan to study the role of nonroad engines in the air toxics 
problem over the next couple of years, and may propose standards if 
appropriate.
2. National, Regional, and Community-based Initiative to Focus on 
Multi-media and Cumulative Risks
    The Clean Air Act requires a number of risk studies to help us 
better characterize risk to the public and the environment from HAPs. 
Information from these studies will provide information for rulemaking 
in some cases but will also provide information to support national and 
local efforts to address risks through other voluntary and pollution 
prevention programs. The following paragraphs describe these studies.
    Utility study. Section 112(n)(1)(A) of the Act requires ``a study 
of the hazards to public health reasonably anticipated to occur as a 
result of emissions by electric utility steam generating units of 
pollutants listed under subsection [112(b)].'' We completed this study 
in February of 1998. We're currently collecting additional information 
to support a determination on whether regulations are appropriate and 
necessary to address risks from HAPs from these sources. We expect all 
test reports required under our information requests by May 31, 2000. 
We'll use this information to conduct additional analysis of the 
emissions of mercury from utilities and potential control technologies. 
In addition, we'll continue the analysis of health-related issues. We 
plan to make our determination about the need for regulation by 
December 15, 2000.
    Great Waters Program. Section 112(m) requires us to monitor, assess 
and report on the deposition of HAPs to the ``Great Waters,'' which 
include the Chesapeake Bay, Lake Champlain, the Great Lakes, National 
Estuary Programs, and National Estuarine Research Reserves. We're 
required to assess deposition to these waters by: establishing a 
deposition monitoring network; investigating the sources of pollution; 
improving monitoring methods; evaluating adverse effects; and sampling 
for the pollutants in aquatic plants and wildlife. Pollutants of 
concern to the Great Waters include mercury, lead, cadmium, nitrogen 
compounds, polycylic organic matter/polynuclear aromatic hydrocarbons 
(POM/PAHs), dioxin and furans, PCBs and seven banned or restricted 
pesticides.
    We're also required to provide an update to Congress every two 
years on any new information relating to deposition of HAPs to the 
Great Waters. We issued the first two reports to Congress in 1994 and 
1997. In addition, in March 1998, we made a determination under section 
112(m)(6) that we have enough authority under the Act to address the 
HAPs impacting the Great Waters. The third report to Congress is 
scheduled for September 1999, and will focus on the contribution of 
atmospheric deposition, environmental and public health effects, 
sources of pollution, and exceedences of standards.
    As part of the Great Waters Program, we're funding special 
monitoring studies at 13 different coastal areas. In addition, we're 
expanding the National Atmospheric Deposition Program to include more 
coastal sites for long-term deposition records. We'll continue to 
develop a coastal monitoring network and to improve air deposition 
monitoring methods.
    In an effort to coordinate programs under the Clean Air Act and the 
Clean Water Act, we're conducting a pilot study to link air dispersion 
and deposition models with watershed fate and transport models. The 
results of this study will help us to improve our multimedia analysis 
efforts and will allow us to look at the connection between our legal 
authorities under the two Acts.
    Mercury study. Section 112(n)(1)(B) requires that we issue a report 
to Congress on the sources and impacts of mercury. We released the 
report in December 1997. The report included an assessment of the 
emissions of mercury from all known anthropogenic sources in the United 
States, the health and environmental implications of these emissions, 
and the availability and cost of control of these emissions.
    Urban Air Toxics Strategy. Section 112(k) of the Act requires us to 
develop a strategy to identify and address risks to the public in urban 
areas. We'll describe the Integrated Urban Air Toxics Strategy in more 
detail in later sections of this document.
3. National Air Toxics Assessments (NATA)
    As mentioned previously, in order for the national air toxics 
program to move to a more risk-based program, it's imperative that we 
have strong analytical tools to support activities to identify risks, 
to track progress toward risk goals and to help prioritize our efforts 
to address emissions and risks from air toxics. Several assessment 
activities are under way to support the national air toxics program, as 
described in the following paragraphs.
    Federal air toxics monitoring. Ambient air toxics information is a 
key component in supporting assessment activities, helping to determine 
exposure, tracking progress of the air toxics program goals, and 
evaluating models and other assessment tools. Because of the importance 
of this information, we're currently developing an approach to 
monitoring air toxics nationally and locally with State and local 
agencies. We envision a monitoring network with some monitors operated 
on the national level to track overall national trends. This monitoring 
network may include both new monitoring sites located for air toxics 
monitoring, as well as information leveraged from other national 
monitoring networks including Photochemical Assessment Monitoring 
Stations (PAMS) (which collect at least eight HAPs) and the PM2.5 sites 
(which collect most of the metals). We'll also compile data from the 
State toxics monitoring networks.
    In order to optimize our monitoring resources, we're working with 
our regulatory partners to expand monitoring networks by adding new 
sites; merging existing Federal and States sites where appropriate 
(e.g., PACS, PM2.5 and Speciation Trends sites); targeting urban 
population-oriented sites; developing a common Acore'' list of 
compounds to monitor; and implementing a phased approach to expanding 
the number of sites and compounds to fill the data gaps.
    Emissions inventories. Over the past several years we've worked to 
build a program for a national inventory of air toxics emissions. We 
now have data sets for the 1990 to 1993 period and a draft for 1996. 
The 1996 National Toxics Inventory (NTI) will be used as part of the 
NATA for modeling and data analyses. It includes information generated 
from MACT standards development, as well as information provided by 36 
States and various industries. The 1996 NTI is currently under review 
by the State and local agencies. We expect the 1996 NTI to be final in 
the fall of 1999.
    Modeling. The NATA will include modeling efforts using information 
from the emissions inventory and supported by the monitoring data. 
We're working toward a future focus on integrated multi-media/
multipathway assessments. We intend to conduct assessments on the 
national, regional, and local scales

[[Page 38711]]

to support activities at all levels of the air toxics program. 
Initially we'll use the Assessment System for Population Exposure 
Nationwide (ASPEN) model (used in the Cumulative Exposure Project) to 
conduct national level assessments.
    In the fall and winter of 1999, we'll conduct national level 
assessments to estimate ambient concentrations of HAP and predict the 
exposures that would result. This information will be released in the 
spring of 2000. These assessments are described in more detail in 
section IV.D.
    In addition, we intend to use air quality and exposure models for 
source-specific assessments and to look at selected urban areas. In the 
near future, we expect to use the Total Risk Integrated Model (TRIM) to 
address local or neighborhood scale applications. This model will have 
the capability to address human health and ecological impacts. We 
expect this to be available late in 2000. In addition, we're working on 
a Models-3/Community Multi-scale Air Quality (CMAQ) Modeling System. 
Initially, this model will support assessments on the urban-to 
regional-scale. Eventually, however, it will be used for neighborhood-
scale assessments. By the end of 2000, we expect to have an operational 
evaluation of the model using mercury and some semi-volatile compounds, 
with a final evaluation completed by 2001. This model includes 
capabilities to address ozone and PM, together with air toxics, and 
will be able to link with a human exposure model.
4. Education and Outreach
    We believe that public participation is vitally important in the 
implementation of the overall air toxics program. We're committed to 
work with cities, communities, State, local and Tribal agencies, and 
other groups and organizations that can help implement our approach to 
reducing toxics emissions. For example, we expect to work with the 
cities, our regulatory partners, and other interested stakeholders in 
the national air toxics assessments that will be conducted. In 
addition, we'll continue to work with stakeholders on regulation 
development. We intend to involve local communities and industries in 
development of local risk initiatives such as the total maximum daily 
load (TMDL) initiatives.

B. Why Are We Concerned About Urban Air in Particular?

    In urban areas, toxic air pollutants raise concerns because sources 
of emissions and people are concentrated in the same geographic area, 
leading to large numbers of people exposed to the emissions of many 
HAPs from many sources. Additionally, while urban exposures to some 
pollutants may be fairly similar across the country, studies in a 
number of urban areas indicate that exposures to other pollutants, and 
any associated risks, may vary significantly from one urban area to the 
next. The tools we rely on in our efforts to better characterize urban 
health risks from air toxics each have associated uncertainties, which 
may add to our concerns. We intend our NATA activities to improve our 
ability to describe these uncertainties and where possible, reduce 
them. As currently available, the various types of information (e.g., 
emissions, ambient air quality monitoring and modeling) that will be 
central to our NATA activities illustrate the importance of focusing on 
urban areas.
    First, our baseline national emissions inventory \10\ for the air 
toxics program indicates that the vast majority of HAP emissions 
(approximately 75 percent of the total HAP emissions of all 188 HAPs 
from all sources) are within counties with urban areas.\11\ 
Additionally, a greater number of different HAPs may be emitted from 
the multiple sources present in urban areas than from the more limited 
number and variety of sources present in rural areas. This is 
particularly important because even in cases where individual pollutant 
levels are low enough that exposure to any one pollutant wouldn't be 
expected to pose harm, some pollutants may work together such that 
their potential for harm increases and exposure to the mixture poses 
harm. Thus, depending on exposure levels and characteristics of the 
pollutants, multiple pollutant exposures, which may be prevalent in 
urban populations, may pose increased public health risks.
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    \10\ The baseline national toxics inventory (NTI) that we've 
compiled over the past few years is representative of the years 
1990-93. We believe that this is an appropriate baseline because 
these years represent the ``pre-MACT'' emissions for HAP sources. 
This baseline inventory contains information on major, area and 
mobile sources for all 188 HAPs and provides information on whether 
the emissions are urban or rural. A subset of this baseline 
inventory is information collected and extensively reviewed by the 
public to support analyses for this Strategy and regulatory actions 
under section 112(c)(6).
    \11\ In estimating the amount of emissions from urban areas, 
we've totaled emissions from all U.S. counties that include a 
metropolitan statistical area with a population greater than 250,000 
or for which more than 50 percent of the population has been 
designated ``urban'' by the U.S. Census Bureau. For a more detailed 
description of emissions allocation, see the emissions information 
prepared to support this Strategy (``Emissions Inventory of 40 
Candidate Section 112(k) Pollutants; Supporting Data for EPA's 
112(k) Regulatory Strategy''), available at www.epa.gov/ttn/uatw/
112k/112kfac.html.
---------------------------------------------------------------------------

    Second, ambient air monitoring information collected by States in 
certain metropolitan areas during the 1990s demonstrate the 
simultaneous presence of many HAPs in urban air and, thus, the 
potential for urban population exposures to multiple HAPs. In assessing 
the implications of these monitored HAP concentrations for potential 
public health concerns, we combined the measured ambient HAP 
concentrations with quantitative estimates of each HAP's cancer 
potency. This limited evaluation of a subset of the small number of 
HAPs monitored indicates the presence of HAPs in some cities that when 
evaluated cumulatively is suggestive of upper bound estimates of 
additional cancer risks at or above one in ten thousand.\12\ This type 
of limited evaluation can provide indications of potential public 
health concerns, but should not be considered a characterization of 
actual health risks.
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    \12\ The technical support documentation for this assessment 
analysis is available from the public docket and includes a 
presentation of ambient monitoring data in 17 cities for a variety 
of HAPs. Also presented are the upper bound estimates of excess 
cancer associated with continuous lifetime exposures at those 
concentrations.
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    Third, an early effort by the Agency to model ambient HAP 
concentrations on a national scale performed for EPA's Cumulative 
Exposure Project (CEP) suggests that HAP exposures are prevalent 
nationwide, and that for some HAPs, in some locations, concentrations 
are significantly higher than the concentrations that, if exposures are 
continuous over a lifetime, are associated with a one-in-one million 
lifetime excess cancer risk.\13\' \14\ As stated above, estimated 
concentrations greater than risk-based concentrations should be viewed 
as indicators of a potential public health problem and not as 
characterizations of actual health risks. Illustrating the need for 
special attention in urban areas, the early modeling analysis found 
that for 75 percent of the HAPs modeled, the average estimated 
concentrations in urban census tracts \15\ were greater, and in some 
cases much greater, than the overall national average concentrations.
---------------------------------------------------------------------------

    \13\ SAIC. 1998. Final Report, Modeling cumulative outdoor 
concentrations of hazardous air pollutants.
    \14\ Woodruff, et al. 1998. Public Health Implications of 1990 
Air Toxics Concentrations across the United States. Environ. Health 
Persp. 106(5):245-251.
    \15\ Census tracts with residential population density greater 
than 750 persons per square kilometer.
---------------------------------------------------------------------------

    The concentration of activities in urban areas leads to the 
presence of multiple emission sources and

[[Page 38712]]

proportionately higher emissions of multiple HAPs. Many of these 
emission sources are area or mobile sources, and their emissions are 
more likely to be released at ground level, where people are more 
likely to be exposed to them. Because approximately 80 percent of the 
U.S. population lives in metropolitan areas,\16\ exposures resulting 
from urban air toxics emissions may pose a significant risk to public 
health. Additionally, the prevalence of minority and low income 
communities in urban industrial and commercial areas, where ambient 
concentrations of HAPs may be greater, increases the likelihood of 
elevated HAP exposures among these subgroups. The potential for air 
toxics in urban areas, either directly or indirectly, to contribute to 
elevated health risks among these and other subgroups (especially 
including children, the elderly and persons with existing illness or 
other potential vulnerability) demonstrates the need to assess risk 
distributions across urban populations in order to address 
disproportionate impacts of air toxics hazards.\17\
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    \16\ U.S. Department of Commerce, 1997, Population Profile of 
the United States. Current population reports, special studies P23-
194. Economic and Statistics Administration, Bureau of the Census, 
Washington, D.C.
    \17\ The reader should note that all of these examples 
illustrate that there are different ways of representing urban 
areas. These are all individually valid, but the result is that 
different definitions lead to different approximations of the 
affected population. In the remainder of the Strategy, we'll explain 
which definition we're using in each particular context.
---------------------------------------------------------------------------

    As described earlier in this notice, we have been and are 
continuing to develop various Federal standards for stationary and 
mobile sources as part of the air toxics program and under other Clean 
Air Act authorities. These standards, as well as standards developed by 
State and local authorities, are expected to improve air quality in 
urban areas. As part of the air toxics program, we will be assessing 
what additional actions, both at the national and local level, are 
needed to further improve air quality in urban areas. This is a primary 
focus of the Integrated Urban Air Toxics Strategy, described more fully 
in the rest of this notice. We will include State and local 
authorities, and in particular mayors, in planning activities to assess 
local air quality and to address concerns.

C. What is the Integrated Urban Air Toxics Strategy?

    The Strategy presented in this notice has been developed in 
response to the requirements of sections 112(k) and 112(c)(3) of the 
Act, and also reflects activities to control mobile source emissions 
required under section 202(l). As stated previously, the Strategy 
represents an integration of our authorities to identify and address 
risks from both stationary and mobile sources. In this section of the 
notice, we describe the goals and major components of the Strategy, 
while later sections describe more fully those components. 
Additionally, section 112(k) of the Act also requires us to report to 
Congress, on two occasions, regarding actions taken under the Strategy 
and current information regarding public health risks posed by HAP 
emissions in urban areas. We're currently preparing the first of these 
two reports to Congress, and its release is planned for later this 
year.
1. Goals of the Strategy
    Our goals for the Strategy reflect both statutory requirements 
stated in section 112(k) and the goals of our overall air toxics 
program. These goals consist of the following:
     Attain a 75-percent reduction in incidence of cancer 
attributable to exposure to HAPs emitted by stationary sources. This is 
relevant to all HAPs from both major and area stationary sources, in 
all urban areas nationwide. Reductions can be the result of actions by 
Federal, State, local and/or Tribal governments, achieved by any 
regulations or voluntary actions.
     Attain a substantial reduction in public health risks 
posed by HAP emissions from area sources. This includes health effects 
other than cancer posed by all HAPs. Reductions can be the result of 
actions by Federal, State, local and/or Tribal governments, achieved by 
any regulations or voluntary actions.
     Address disproportionate impacts of air toxics hazards 
across urban areas. This will necessarily involve consideration of both 
stationary and mobile source emissions of all HAPs, as well as sources 
of HAPs in indoor air. We intend to characterize exposure and risk 
distributions both geographically and demographically. This will 
include particular emphasis on highly exposed individuals (such as 
those in geographic Ahot spots'') and specific population subgroups 
(e.g., children, the elderly, and low-income communities).
    The Act includes certain specific requirements for the Strategy. 
First, we're required to identify at least 30 HAPs, ``which, as the 
result of emissions from area sources, present the greatest threat to 
public health in the largest number of urban areas'' (section 
112(k)(3)(B)(i) of the Act). Second, we're required to assure that 
sources accounting for 90 percent of the emissions of identified area 
source HAPs are subject to standards (section 112(k)(3)(B)(ii) and 
section 112(c)(3)). These steps will contribute to our progress toward 
the Strategy's goals.
    In meeting the Strategy's goals, we'll consider reductions in HAPs 
resulting, not only from actions under our overall air toxics program 
(e.g., MACT, residual risk standards, mobile source emission controls) 
and measures resulting from programs to attain the national ambient air 
quality standards for particulate matter and ozone (as well as our 
other regulatory programs), but also from State, local and Tribal 
measures. Further, we'll consider cumulative risks presented by 
exposures to emissions of HAPs from sources in the aggregate. This is 
consistent with the language of section 112(k)(1) of the Act, quoted 
earlier. Further, consistent with the direction of section 112(k)(4) to 
encourage and support area-wide strategies developed by State or local 
air pollution control agencies, we'll work with State, local, and 
Tribal air pollution control programs for additional progress toward 
these goals.
    Continuous advances in our knowledge and activities within the 
broader air toxics program, both of which are expected to contribute 
especially relevant information, will be integral to the implementation 
of the Strategy. For example, certain air toxics, such as mercury, may 
be deposited from the air into soil and/or water, taken up by organisms 
into the food chain, and bioaccumulate so that concentrations increase 
through each level of the food chain. The result is that humans and 
wildlife can be exposed to these ``air'' toxics by eating contaminated 
food, especially predatory fish from affected water bodies. We're 
concerned about individuals in urban areas that eat more than the 
average amount of fish from local sources, including urban subsistence 
fishers. Under the Great Waters program, we monitor air toxics 
deposition and evaluate potential adverse effects on public health and 
the environment including those related to contaminated ecosystems and 
fish. This information will assist us in assessing the potential for 
certain HAPs to pose multipathway health risks to urban residents of 
coastal areas (e.g., risks from both inhalation of HAPs and consumption 
of fish contaminated by deposition of HAPs to waterways).
    The indoor environments program is another Agency activity with 
particular relevance to the Strategy because people in urban settings 
spend as much as 80

[[Page 38713]]

to 90 percent of their time indoors.\18\ Additionally, outdoor air is 
brought indoors through infiltration and mechanical ventilation and 
there are also many sources of air toxics indoors. As part of this 
Strategy, EPA will assess the current information on indoor emissions 
and air concentrations of air toxics, and will use the data, to the 
extent possible, to estimate exposures to air toxics in indoor 
environments. As we continue to develop and enhance our knowledge of 
exposures and risks from indoor air toxics through the indoor 
environments program, we'll seek to include information on indoor 
exposures in our characterization of risk associated with outdoor 
sources and in the development of risk management options for air 
toxics. We also intend to conduct additional research on indoor air 
exposures to HAPs and on the relative significance of outdoor and 
indoor concentrations of HAPs, as well as on the relationship between 
outdoor emission sources and indoor concentrations of HAPs.
---------------------------------------------------------------------------

    \18\ The indoor environments program is a non-regulatory 
program, working under the authority of Superfund Amendments and 
Reauthorization Act (SARA) Title IV to perform research and provide 
information to the public on the health problems associated with air 
pollutants in the indoor environment. Most of the guidance provided 
by the indoor environments program focuses on reducing pollutants 
throughout buildings through proper building design, operation, and 
maintenance, including management of indoor sources. The program 
works through an extensive network of partners in providing training 
and information on indoor air environmental issues throughout the 
United States.
---------------------------------------------------------------------------

2. Developing the Strategy
    To address the problem of exposure to air toxics in urban areas, we 
published a draft strategy on September 14, 1998 (63 FR 49240) that 
addressed the urban air toxics risks from both stationary and mobile 
sources. We asked for, and received, extensive public comment on the 
draft strategy. We received over 120 letters and heard from numerous 
speakers at stakeholder meetings in Alexandria, VA; Durham, NC; 
Chicago, IL; and San Francisco, CA, as well as at other meetings 
including a public meeting in New York City and meetings with the 
National Environmental Justice Advisory Council. As discussed 
throughout the following sections of this notice, we considered these 
comments in developing the final Strategy. Comment letters, meeting 
summaries, and material developed to analyze and respond to comments 
are in the public docket (Docket No. A-97-44).
    The Strategy being published today will produce a set of actions in 
response to the cumulative public health risks presented by exposures 
to emissions of multiple HAPs from multiple sources. We believe that by 
considering urban air toxics emissions from all sources, we'll better 
understand and address the relative risks posed by any one pollutant 
and/or source category. Thus, by integrating activities under different 
parts of the Act, we can more realistically address aggregate exposure 
in areas where the emissions and risks are most significant and 
controls are the most cost effective.
3. Components of the Strategy
    Consistent with the broader overall air toxics program (described 
in section I.A.), the Strategy is made up of four interrelated parts or 
components for addressing the public health risk associated with urban 
air toxics. Information from each of the four components provides 
feedback to the others to inform the decisions needed to make progress 
toward meeting our goals.
    The first component includes our regulatory tools and programmatic 
activities for source-specific and sector-based standard setting, as 
well as those of States, local agencies, and Tribes, which contribute 
to reductions in emissions of air toxics from major, area, and mobile 
sources. This component includes activities such as selecting urban 
HAPs, setting emission standards, conducting studies, developing 
policies, and conducting enforcement and compliance assistance 
activities. These actions result in emission reductions, as well as 
associated reductions in risk. Sections II and III of this document 
describe the regulatory activities we'll pursue to implement the 
Strategy.
    The second component of the Strategy involves local and community-
based initiatives to focus on multi-media and cumulative risks within 
urban areas. These may include activities such as pilot projects to 
identify and address risk, and may rely on some of the assessment 
activities and tools described below. Section III of this document 
describes the nature of some of these activities.
    The third component is the urban component of NATA, which will 
provide us with meaningful information and allow us to describe 
progress that we've made in meeting our overall program and strategy-
specific goals. We'll identify the pollutants and sources that 
contribute to any failures in meeting our risk reduction goals, and 
provide meaningful information to support regulatory and policy 
decisions needed to move us closer to meeting them. Section IV of this 
document, Assessment Activities, describes how we'll design and conduct 
these assessments. These activities rely on our improving base of 
knowledge (e.g., concerning health effects and exposure 
characteristics) and tools (e.g., emissions inventories, monitoring 
networks, and computer models), which are described in section V, along 
with our plans for their improvement and related research.
    The fourth component, communicating about risk through education 
and outreach to the public, ensures that the activities we undertake 
are responsive to your concerns. We'll depend on stakeholder 
involvement at the national and local levels to implement the Strategy. 
Section VI explains how we'll communicate with the public on these 
issues.
    We've formulated an integrated Strategy to characterize, 
prioritize, and equitably address the public health impacts of HAPs in 
urban areas. The Strategy relies on a strategic combination of 
regulatory approaches and voluntary partnerships, both of which are 
based on ongoing research and assessments, and include educational 
outreach. Sections II through VI of this document explain how the 
components described above work, how they'll be expanded and improved, 
and how we expect to meet our goals to reduce risk from HAPs.
4. Overview of the Strategy
    The Integrated Urban Air Toxics Strategy, in conjunction with the 
overall air toxics program, will continue to lower human exposure to 
air toxics by reducing emissions. Progress will be achieved by:
     Completing MACT standards.
     Addressing residual risk.
     Implementing the urban air toxics strategy.
     Enhancing our ability to characterize risk and estimate 
exposures.
     Developing new tools for monitoring progress with the 
goals of the air toxics program.
     Developing a monitoring network.
     Effectively implementing and enforcing standards.
    We'll achieve these objectives by following the guiding principles 
of the air toxics program:
     Working cooperatively and effectively with State and local 
communities.
     Focusing on communities, susceptible populations, and 
sensitive ecosystems.
     Providing cost-effective, common-sense solutions to 
problems, through flexible strategies.
     Developing and executing an effective education and 
outreach program.

[[Page 38714]]

    The Strategy will bring together the four basic components 
(standards, initiatives, assessment, and outreach). It will be an 
iterative and evolving process that will use existing programs and 
tools to target risk reduction and to continually assess risk and 
measure progress.

II. Federal Activities Related to the Integrated Urban Air Toxics 
Strategy

A. What HAPs Pose the Greatest Threat in Urban Areas?

    This section provides further discussion of what air toxics are, 
the concerns they present, and describes how we evaluated and selected 
a list of HAPs to guide our actions under the Strategy. In brief, we 
evaluated the health effects information available for the 188 HAPs, 
estimated emissions from all known sources using a variety of 
techniques, assessed available air quality monitoring data, reviewed 
existing studies, and produced a list of pollutants based on the 
relative hazards they pose in urban areas, considering toxicity, 
emissions, and related characteristics. From this effort, we 
established a list of urban HAPs which pose the greatest threats to 
public health in urban areas, considering emissions from major, area 
and mobile sources. Among these urban HAPs are a subset of the 30 HAPs 
having the greatest emissions contribution from area sources (the 
``area source HAPs'').
1. Air Toxics Defined
    Section 112(b) of the Act identifies 188 toxic chemicals as HAPs. 
Hazardous air pollutants include a wide variety of organic and 
inorganic substances released from industrial operations (both large 
and small), fossil fuel combustion, gasoline and diesel-powered 
vehicles, and many other sources. The major categories of toxic air 
pollutants include volatile organic compounds (known as VOCs), metals 
and inorganic chemicals, and semi-volatile organic chemicals. Volatile 
chemicals are usually released into the air as vapor, while semi-
volatile organics and metals may be released in the form of particles. 
Additionally, 17 of the 188 HAPs are defined as chemical groups rather 
than unique chemicals. In evaluating the health effects, emissions and 
monitoring information for these chemical groups we made specific 
decisions regarding our treatment of the available information for the 
group or the individual chemicals represented by the group (see the 
technical support document in the public docket for the identification 
of the urban HAPs).
    Of the 17 chemical groups, polycyclic organic matter (POM) posed 
particular complications. Polycyclic organic matter is defined in 
section 112(b) of the Act as organic compounds with more than one 
benzene ring and a boiling point greater than or equal to 100  deg.C, 
which encompasses a complex mixture of thousands of polynuclear 
aromatic hydrocarbons (PAH). Among the many PAH constituents of POM are 
seven compounds (benzo[a]anthracene, benzo[a]pyrene, 
benzo[b]fluoranthene, benzo[k]fluoranthene, chrysene, 
dibenzo[a,h]anthracene, and indeno[1,2,3-c,d]pyrene) that we've 
identified as probable human carcinogens. For the evaluation of POM as 
a potential public health threat in urban areas, and for the subsequent 
source category analysis, we used this group (referred to as 7-PAH) as 
a surrogate for the much larger, more complex and diverse mixture of 
POM.
    The 188 HAPs have been associated with a wide variety of adverse 
health effects, including cancer, neurological effects, reproductive 
effects and developmental effects. Additionally, the specific health 
effects associated with the various HAPs may differ, depending on the 
particular circumstances of exposure (e.g., the amount of chemical, the 
length of time a person is exposed, the stage in life of the person 
exposed). We've classified many of the HAPs as ``known,'' ``probable,'' 
or ``possible'' human carcinogens and have included this information in 
our Integrated Risk Information System.\19\ The HAPs can also be 
described with regard to the part of the human body to which they pose 
threats of harm. For example, neurotoxic pollutants cause harm to the 
nervous system. Other effects include cardiovascular, and respiratory 
effects, as well as effects on the immune system and reproductive 
system. The severity of harm can range from headaches and nausea to 
respiratory arrest and death. The level of severity differs both with 
the amount and length of exposure and the chemical itself (e.g., how it 
interacts with individual components of the nervous system). Some 
chemicals pose particular hazards to people of a certain age or stage 
in life or even based on their ethnic background. For example, some 
HAPs are developmental toxicants. That is, exposure to certain amounts 
of these chemicals during a woman's pregnancy or exposure of infants or 
children can prevent normal development into a healthy adult. Other 
HAPs are reproductive toxicants, meaning they may have the potential to 
affect the ability of adults to conceive or give birth to a healthy 
baby.
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    \19\ The Integrated Risk Information System (IRIS), prepared and 
maintained here at EPA, is an electronic data base containing 
information on human health effects that may result from exposure to 
various chemicals in the environment. IRIS was initially developed 
in response to a growing demand for consistent information on 
chemical substances for use in risk assessments, decision-making and 
regulatory activities. The information in IRIS is intended for those 
without extensive training in toxicology, but with some knowledge of 
health sciences. Further information about IRIS, including the 
information it contains, can be found on the IRIS website at http://
www.epa.gov/iris.
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    In addition, we're currently investigating the health risks 
associated with the mixture of compounds that comprise diesel exhaust 
which originates primarily from mobile sources. While not specifically 
listed as one of the 188 HAPs, diesel exhaust includes many HAPs, 
including chemicals that fall into the group of POM chemicals, as well 
as some HAP metals and volatile organic compounds. In addition, we're 
concerned about the potential health risks from the particulate matter 
component of diesel exhaust. Diesel particles are characteristically 
small and fall within the size range of inhalable particles addressed 
by the national ambient air quality standards for particulate 
matter.\20\ Our draft health assessment of diesel emissions identifies 
lung cancer as well as several other adverse respiratory health 
effects, including respiratory tract irritation, immunological effects, 
and changes in lung function, as possible concerns for long-term 
exposures to diesel exhaust.\21\ If new diesel engine models are used 
in an increasing share of the light duty fleet,\22\ concerns regarding 
potential

[[Page 38715]]

health risks from diesel exhaust will become more significant.
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    \20\ Inhalable particles are defined as particles of aerodynamic 
diameter less than or equal to 10 micrometers.
    \21\ Health Assessment Document for Diesel Emissions, SAB Review 
Draft, U.S. Environmental Protection Agency, Washington, D.C. EPA/
600/8-90-057C, February 1998. The evidence comes from studies 
involving occupational exposures and/or high exposure animal 
studies. The Health Assessment, when completed, will recommend how 
the data should be interpreted for lower environmental levels of 
exposure. The draft Health Assessment is currently being revised to 
address comments from a peer review panel of the Clean Air Science 
Advisory Committee (CASAC Review of the Draft Diesel Health 
Assessment Document, U.S. Environmental Protection Agency Science 
Advisory Board, Washington, D.C. EPA-SAB-CASC-99-001. The CASAC will 
review these revisions later this year.)
    \22\ Diesel engines in highway and nonroad mobile sources are 
numerous and widespread. Heavy-duty highway and nonroad diesel 
engines are the largest sources of diesel exhaust emissions. While 
diesel engines are used in a relatively small number of cars and 
light-duty trucks today, vehicle and engine manufacturers are 
developing new engine models that may be used in an increasing share 
of the light-duty fleet, particularly light-duty trucks.
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    As described above, HAPs and mixtures containing HAPs have the 
potential to pose a variety of health risks depending on their chemical 
characteristics, as well as the circumstances of human exposure. In the 
following two sections, we describe our identification of HAPs of 
particular concern in urban areas nationally.
2. The URBAN HAPs
    Although information is limited regarding actual health risks posed 
by specific HAP emissions, the availability of various other types of 
information is sufficient to achieve our objective of identifying those 
HAPs posing the greatest potential public health concern in the largest 
number of urban areas. For the purpose of meeting the requirements of 
section 112(k) and section 112(c)(3), we've listed in Table 1 the 33 
HAPs that, on a national scale, we believe pose the greatest threat to 
public health in the largest number of urban areas. Of these 33 HAPs, 
29 appeared on the draft urban HAPs list published in our September 14, 
1998 Federal Register document (63 FR 49240). Changes to the list 
resulted from changes made to the method for urban HAPs selection, the 
input data and the final selection criteria upon consideration of 
comments received on the draft list and its supporting methodology. 
\23\
---------------------------------------------------------------------------

    \23\ The final list includes beryllium compounds, 
hexachlorobenzene, polychlorinated biphenyls and 1,1,2,2 
tetrachloroethane, which hadn't appeared on the draft list, and 
doesn't include bis(2-ethylhexyl)phthalate (DEHP), 1,4-
dichlorobenzene, methyl chloride and methylene diphenyl diisocyanate 
(MDI), which were on the draft list.

    Table 1.--List of Urban HAPs for the Integrated Urban Air Toxics
                                Strategy
                          [``Urban HAPs List'']
------------------------------------------------------------------------
                           HAP                              CAS No.+HAP
------------------------------------------------------------------------
acetaldehyde............................................           75070
acrolein................................................          107028
acrylonitrile...........................................          107131
arsenic compounds.......................................  ..............
benzene.................................................           71432
beryllium compounds.....................................  ..............
1,3-butadiene...........................................          106990
cadmium compounds.......................................  ..............
carbon tetrachloride*...................................           56235
chloroform..............................................           67663
chromium compounds......................................  ..............
coke oven emissions*....................................         8007452
1,2-dibromoethane*......................................          106934
1,2-dichloropropane (propylene dichloride)..............           78875
1,3-dichloropropene.....................................          542756
ethylene dichloride (1,2-dichloroethane)................          107062
ethylene oxide..........................................           75218
formaldehyde............................................           50000
hexachlorobenzene.......................................          118741
hydrazine...............................................          302012
lead compounds..........................................  ..............
manganese compounds.....................................  ..............
mercury compounds.......................................  ..............
methylene chloride (dichloromethane)....................           75092
nickel compounds........................................  ..............
polychlorinated biphenyls (PCBs)........................         1336363
polycyclic organic matter (POM).........................  ..............
quinoline...............................................           91225
2,3,7,8-tetrachlorodibenzo-p-dioxin (and congeners and           1746016
 TCDF congeners)........................................
1,1,2,2-tetrachloroethane...............................           79345
tetrachloroethylene (perchloroethylene).................          127184
trichloroethylene.......................................           79016
vinyl chloride..........................................          75014
------------------------------------------------------------------------
+ Chemical Abstracts System number.
* HAPs with less significant emissions contributions from area sources.

    This list of 33 urban HAPs includes not only those with emissions 
from area sources, but reflects the integrated nature of the Strategy 
by including those posing public health concerns in urban areas 
regardless of emissions source type. Included among the 33 urban HAPs 
are the 30 HAPs with greatest emissions contributions from area sources 
(i.e., the area source HAPs'').
    In response to publication of our draft list of urban HAPs, we 
received comments regarding our inclusion of HAPs emitted predominantly 
from non-area sources. Several commenters said that it was 
inappropriate to include HAPs for which area source contribution was 
low or negligible. Although section 112(k)(3)(B)(i) only requires that 
we list HAPs emitted from area sources, we believe that the public is 
exposed to complex mixtures of pollutants, and that these pollutants 
are emitted by all types of sources. In other words, the risk from 
exposure to HAPs has public health implications regardless of the 
source or source type from which they are emitted. Therefore, in the 
interests of best protecting public health in urban areas, we've listed 
the 33 HAPs in Table 1 considering the aggregate exposure potential of 
mobile,

[[Page 38716]]

area, and major stationary source emissions combined. At the same time, 
as described below, we've also identified the 30 HAPs with the greatest 
area source contribution. Under section 112(k), there aren't any 
specific regulatory implications of listing the other three HAPs. 
However, we'll use all 33 HAPs in prioritizing efforts to address risk.
    Section 112(k)(3)(B) of the Act requires us to identify not less 
than 30 HAPs that are estimated to pose the greatest threat to public 
health in the largest number of urban areas ``as the result of 
emissions from area sources.'' The Act, however, doesn't state that 
such threats must be exclusively the result of emissions from area 
sources. Therefore, from the list of 33 urban HAPs (i.e., the HAPs that 
pose the greatest threat to public health in urban areas because they 
ranked highest relative to the other HAPs in the analysis discussed 
above), we identified those 30 HAPs with the greatest contributions of 
national urban emissions from area sources, thus ensuring consistency 
with the specification in section 112(k)(3)(B)(i). Without these 
contributions from area sources, the threat from these HAPs would not 
be as great. Emissions of only the 30 area source HAPs were considered 
in the area source category listing required under section 112(c)(3) 
and section 112(k) and described in section II.B. of this document. The 
other three HAPs in Table 1 for which area sources are less significant 
contributors to total emissions (i.e., those HAPs noted on Table 1 with 
an asterisk), can be addressed, as appropriate, using our other 
existing authorities, as described in section II.C. of this document.
    During the public comment period on the draft Strategy, we received 
substantial comment regarding the role of diesel engine emissions among 
urban air pollutants, with several commenters suggesting that we 
include diesel exhaust among the priority urban HAPs. As described 
earlier, diesel exhaust, although not specifically listed among the 188 
HAPs in section 112(b) of the Act, is a particular type of emission 
which is composed of many HAPs. We agree with commenters that diesel 
exhaust plays an important role among urban air pollutants, and, as 
previously mentioned, we're investigating the health risks associated 
with diesel exhaust. Meanwhile, we plan to address diesel exhaust in 
our section 202(l) rulemaking for air toxics from motor vehicles and 
their fuels.
    It's important to note that the list in Table 1 was generated based 
on our best estimates representing 1990 national baseline air toxics 
emissions and ambient concentrations for urban areas. For example, 
implementation of technology-based standards for coke ovens has reduced 
the benzene, coke oven gases, and POM from these sources by 80 percent 
(or 1,408 tons per year) since 1993. In addition, certain urban areas 
have reduced other benzene emissions by as much as 30 or 40 percent. 
Much of this reduction is attributable to the implementation of mobile 
source reformulated gasoline requirements. To insure that we 
appropriately target reductions of urban air toxics to support the 
protection of public health, it will be important to reevaluate our 
priorities as we develop emissions estimates and obtain more 
comprehensive monitoring information for more recent years.
3. Method to Identify the Urban HAPs.
    This section summarizes how we identified HAPs for the urban HAPs 
list. Our identification methodology included three separate analyses. 
The results of these analyses were compared using specific criteria in 
order to identify the urban HAPs. The three analyses relied on a 
variety of information types including toxicity information, emissions 
estimates, ambient monitoring, and air quality modeling. The 
methodology is summarized here and more fully described in the 
technical support document (``Ranking and Selection of Hazardous Air 
Pollutants''), which is available through the public docket and on our 
website.
    In 1997, we conducted an initial screening evaluation using a 
preliminary methodology. In addition to identifying HAPs for which we 
separately conducted a public review of our national emissions 
inventory information, this evaluation provided us with the opportunity 
for peer review of our preliminary methodology. Like the methodology 
relied on for our final list, this preliminary methodology relied on 
various types of information relevant to potential health risks posed 
by the 188 HAPs, and it integrated the results of three relative 
rankings using the different types of information. This initial 
screening run provided a starting point for focusing improvements in 
the national emissions inventory and for evaluating and refining our 
methodology for selecting the list of urban HAPs.
    The preliminary methodology and screening analysis were reviewed by 
a panel of outside experts. In early January of 1998, the preliminary 
methodology was presented to the peer review panel in a written report. 
A full day session of the peer review panel was held on January 21, 
1998 to discuss the methodology and underlying data. The reviewers 
evaluated all facets of the methodology and its suitability for 
identifying HAPs for the urban HAPs list, the relative value of various 
data sources, the availability of additional data sources, the 
scientific validity of assumptions, consistency across the methodology 
and appropriate presentation formats. Reviewers provided oral comments 
at the January 21 meeting, as well as written comments before and after 
the meeting. The final methodology described here has incorporated 
revisions made to address comments raised by the January 1998 peer 
review.
    Comments were also received from the public in response to our 
publication of the draft list of urban HAPs (September 14, 1998, 63 FR 
49240). Consideration of issues raised by some commenters led us to 
modify certain aspects of both the identification methodology and the 
underlying data inputs. These changes were not inconsistent with 
recommendations made by the 1998 peer review panel. Consistent with 
peer reviewer recommendations to use the available information in the 
most robust manner, our final identification methodology integrates the 
results of three separate analyses. These ranking analyses are 
discussed in the following sections. Because each analysis focused on 
different aspects of the available information, such that no one 
analysis fully captured all important aspects of the urban air toxics 
information, we and the peer reviewers agreed that all three of the 
analyses should be performed and their results integrated, to yield a 
more comprehensive methodology.
    a. Analysis 1: Risk-related ranking indices. In the first of the 
three analyses, we ranked HAPs by combining surrogates for toxicity 
with surrogates for exposure into ranking indices. The surrogates for 
toxicity were risk-based concentrations (RBCs) for inhalation or risk-
based doses (RBDs) for ingestion. The RBCs and RBDs were derived from 
acute and chronic (cancer and non-cancer) health-based reference 
values.\24\
---------------------------------------------------------------------------

    \24\ Acute RBCs were set equal to risk management exposure 
guideline levels (e.g., Acute Exposure Guideline Levels (62 FR 
58839-51) or Emergency Response Planning Guidelines (American 
Industrial Hygiene Association, 1998. Emergency response planning 
guidelines and workplace environmental exposure guidelines.) for 
mild, transient or no effects from short exposure periods, when 
available. Additionally, two chronic RBCs and two chronic RBDs were 
derived for each HAP for which the requisite data were available. 
For carcinogenic HAPs, we compared the continuous exposure levels 
associated with predicted upper-bound lifetime increased cancer 
risks of one-in-one million and one-in-ten thousand to the 
continuous exposure level (e.g., EPA's reference concentration) 
estimated to be without adverse non-cancer effects in human 
populations, including sensitive subgroups. We then set the two 
chronic RBC or RBD values to the lower two of those three levels. 
For other HAPs, both of the two chronic RBC or RBD values were set 
to the continuous exposure level estimated to be without adverse 
non-cancer effects in human populations, including sensitive 
subgroups. A fuller discussion of these steps is included in the 
technical support document.

---------------------------------------------------------------------------

[[Page 38717]]

    Types of information used as surrogates for exposure included 
measured ambient concentrations and yearly emission estimates from 
area, major and mobile sources in all urban areas nationwide. To 
address the potential for certain HAPs to pose significant risks of 
exposure through pathways other than inhalation (primarily by consuming 
food with accumulated HAPs), one set of indices also incorporated 
measures of bioaccumulation potential. As described in more detail in 
the technical support document, a total of seven separate indices \25\ 
were calculated using these different types of toxicity and exposure 
information. Lack of the requisite data prevented all seven indices 
from being calculated for all of the 188 HAPs. The indices were 
combined into a single HAP ranking.
---------------------------------------------------------------------------

    \25\ Four of the indices relied on chronic RBCs and emissions or 
monitoring information, two other indices relied on chronic RBDs 
plus emissions and bioaccumulation information, and the seventh 
index relied on acute RBCs and monitoring information.
---------------------------------------------------------------------------

    During the public comment period, we received comments stating that 
the role of monitoring information in the methodology should be 
strengthened. Because ambient concentrations directly influence 
people's exposure to HAPs and there are differences among HAPs in the 
many variables affecting their behavior after being emitted into the 
air, we agree that it is important that the monitoring information play 
a strong role in this analysis. Relying solely on emissions information 
in selection of the urban HAPs would ignore the many factors which 
influence ambient HAP concentrations. Since the publication of the 
draft list, we've expanded our monitoring database to increase both the 
number of pollutants for which we have monitoring information and the 
number of measurement values. We've also improved our treatment of non-
detect measurements, first by assuming undetected HAPs are present at 
one half the detection limit (instead of omitting the observation), and 
by omitting data altogether for HAPs having fewer than ten percent of 
observations above the detection limit. These changes have improved the 
technical basis of the ambient indices.
    We also received comment stating that inappropriate weight was 
assigned to those HAPs for which the acute index was developed. In the 
analysis for the draft Strategy, the requisite information for 
calculating this index (both an acute RBC and an estimate of short-term 
peak exposure) were available for only 21 of the 188 HAPs. We 
appreciate the issue raised by the commenter that, because of the 
relatively small number of HAPs for which this index could be 
calculated, it was not necessarily assigning HAPs the appropriate 
emphasis. Through our improvements to the ambient database described 
above, and by increasing the number of acute RBCs, we have addressed 
this issue and reduced bias in this index.
    Commenters also recommended increased emphasis on persistent, 
bioaccumulative and multipathway pollutants for which non-inhalation 
exposure pathways may be important. It's important to recognize that 
persistent bioaccumulative toxics (PBTs) are also often multipathway 
pollutants, because the pattern of exposure is frequently other than 
inhalation. However, not all multipathway pollutants are PBTs.
    One commenter said ``EPA should consider multi-pathway exposures 
under 112(k) when there is sufficient evidence demonstrating that 
airborne emissions of the listed HAP have both direct and indirect 
exposure pathways, which have been clearly identified.'' Another said, 
``It is appropriate to include compounds with exposure pathways other 
than inhalation because these pathways are a true concern in urban 
areas where atmospheric deposition of particulate phase HAPs is 
occurring (i.e., lead, mercury, cadmium, dioxin and PCBs) and being 
taken up by fish, garden vegetables or hand-to mouth activity observed 
in infants.'' With regard to the PBTs, some commenters said PBTs should 
have been given more thorough consideration for listing. They said the 
risks from PBT exposure are high, and the concentrations of many PBTs 
are higher in the urban than non-urban areas. We support the use of the 
multipathway analysis to assess total human exposure, particularly in 
the case of PBTs.
    Additionally, commenters said that indices should be calculated so 
that the size of index value differences among HAPs could be more 
clearly observed, and any bias related to different numbers of HAPs 
ranked by each index removed. Because we believe that both of these 
issues are important, we changed the index calculation methodology to 
address these recommendations. This change had its greatest impact on 
the food chain pathway index, in which HAPs with high bioaccumulation 
potential and ingestion toxicity received much higher index values. 
Primarily as a result of this change, Table 1 now includes two 
additional persistent, bioaccumulative HAPs--PCBs and 
hexachlorobenzene--that were absent from the September 1998 draft list. 
Hexachlorobenzene and PCBs, as well as mercury, cadmium, lead, POM and 
dioxin (also identified as urban HAPs in Table 1), are among the 
pollutants of concern for our Great Waters program. Additionally, PCBs, 
mercury and dioxin were identified as pollutants of concern in the 
Great Lakes by the International Joint Commission of the United States 
and Canada. Hexachlorobenzene, PCBs, dioxins, mercury, and alkyl-lead 
were targeted for virtual elimination in the Great Lakes in the 1997 
Canada-United States ``Strategy for the Virtual Elimination of 
Persistent Toxic Substances in the Great Lakes'', known as the 
``Binational Toxics Strategy''.
    Some commenters said that the identification methodology emphasized 
cancer as a health effect and didn't consider other health effects 
including asthma, birth defects and reproductive effects. The 
methodology does, however, consider health effects other than cancer. 
Reference values (RBCs and RBDs) for each HAP used in the analysis were 
developed for the health effects believed to occur at the lowest 
exposure. In the case of HAPs which, in addition to these other health 
effects, also pose cancer risks, we developed RBC/RBD values for one-
in-one million and one-in-ten thousand predicted lifetime cancer risk 
levels. These risk levels have historically been used to inform 
environmental regulatory action. The cancer risk-based values were 
compared to RBC/RBD values for the most sensitive non-cancer health 
effect, and the lowest two RBC/RBD values for each HAP were used in the 
calculation of the chronic indices. This step, and the inclusion among 
the seven indices of an acute toxicity index based entirely on effects 
other than cancer, was intended specifically to recognize the 
importance of health effects other than cancer for some HAPs. Thus, we 
believe that the assessment methodology provides a balanced 
consideration of all health effects associated with each HAP, with 
index calculation and the resultant ranking depending significantly on 
effects other than cancer.
    We also received comments regarding the toxicity information used 
in the analysis. More specifically, commenters

[[Page 38718]]

suggested that in the case of 1,3-butadiene and vinyl chloride, we 
should rely on draft assessments in progress rather than on assessments 
currently available on IRIS. In the case of 1,3-butadiene, we agree 
that the IRIS risk estimate is not an appropriate basis from which to 
extrapolate human risk and the updated assessment has progressed to the 
point where it is appropriate for use here.\26\ Use of this new 
assessment, however, does not affect the presence of 1,3-butadiene on 
the urban HAPs list. In the case of vinyl chloride, we've chosen to use 
the Agency consensus assessment currently in IRIS rather than a draft 
assessment that may yet change significantly. However, we've confirmed 
that using the draft assessment for vinyl chloride wouldn't change its 
status on the final urban HAPs list.
---------------------------------------------------------------------------

    \26\ See April 27, 1999 internal memo, available in the public 
docket.
---------------------------------------------------------------------------

    Some commenters questioned the use of cancer-based RBC or RBD 
values for certain HAPs to which the Agency has assigned a ``C'' weight 
of evidence for carcinogenicity (``possible human carcinogens''). We 
evaluated the supporting data for each ``C'' carcinogen that had been 
proposed for listing to verify the appropriateness of the assessments 
for use in this analysis. Many of these substances are currently the 
subjects of research studies and EPA reassessment activities. In the 
case of 1,4-dichlorobenzene, the currently available information led us 
to modify our analysis so that the RBC and RBD values were based on 
effects other than cancer. For all other ``C'' carcinogens, we retained 
the RBC and RBD values. As updated information and assessments become 
available for these and other HAPs, we intend to use that information 
in analyses supporting future regulatory actions under the Strategy.
    Other commenters questioned our assumptions as to the predominant 
species of chromium and nickel in emissions and monitoring data. 
Because the national monitoring and emissions data used in this 
analysis don't differentiate among species of metals, we had to make 
certain assumptions. To address the likelihood, supported by limited 
available data, that all nickel present in emissions or ambient air 
isn't in the form that is thought to have carcinogenic potential (e.g., 
nickel subsulfide and other insoluble forms), we applied the cancer-
based RBC for nickel subsulfide to 25 percent of the total emissions 
and the ambient measurements for total nickel. We based this decision 
on the assumption that no more than 50 percent of ambient nickel is 
present in the insoluble form and no more than 50 percent of that is 
present in the crystalline form. In the case of the ingestion pathway, 
the non-cancer-based RBD was used. Regarding chromium, the limited 
emissions and monitoring information available for both hexavalent and 
total chromium indicated that approximately two thirds of the chromium 
present in ambient air or national emissions is likely to be other than 
the hexavalent form. Thus, we applied the cancer-based RBC for 
hexavalent chromium to 35 percent of the total emissions and to 35 
percent of the ambient measurement.
    A few commenters requested an analysis of uncertainties surrounding 
the calculations. To the extent that it's possible to conduct an 
uncertainty analysis, we believe the process already includes one. The 
calculation and presentation of seven different ranking indices, 
instituted in response to comments from the January 1998 peer review 
panel, is presented in graphic form in the technical support document. 
These graphs show the range of ranking indices for each HAP, which we 
regard as a measure of some of the uncertainty associated with this 
identification methodology.
    b. Analysis 2: Review of existing risk assessments and hazard 
rankings. For the second analysis, we reviewed a number of air toxics 
risk assessments or hazard rankings conducted previously by EPA staff, 
State agencies or others.\27\ We selected 14 of the available studies 
for use in this analysis, because they were sufficiently broad in the 
pollutants evaluated, they included area sources of HAPs, and they 
focused on the risks presented in urban areas. Each study provided a 
risk-based ranking of HAPs, with separate rankings for cancer and, when 
available, other health effects. The rankings within each study were 
converted to a scale common to all of the studies, and the values were 
summed across the studies, providing a total score for each HAP. 
Because section 112(k) places special emphasis on area sources of HAPs, 
scores were developed both for studies that considered combined 
emissions from major, area, and mobile sources, and for studies that 
considered emissions from area sources alone. From this analysis, we 
identified those HAPs that, when compared across studies, consistently 
ranked high.
---------------------------------------------------------------------------

    \27\ These assessments and rankings, and the details of this 
analysis, are described in the technical support document for the 
identification of the urban HAPs, which is available in the public 
docket.
---------------------------------------------------------------------------

    c. Analysis 3: Cumulative Exposure Project (CEP). In the third 
analysis, we used information provided by the CEP.\28\ In the CEP, the 
Assessment System for Population Exposure Nationwide (ASPEN) model was 
used with preliminary estimates of 1990 HAP emissions from all source 
types to predict long-term average concentrations at the census tract 
level for 148 HAPs. For some pollutants, modeled concentrations were 
augmented with estimates of background levels that were intended to 
represent contributions from natural sources, as well as historic 
emissions of persistent pollutants. The estimated ambient 
concentrations were then compared to risk-based concentrations (termed 
benchmarks by the authors) intended to represent either continuous 
exposure levels associated with a one-in-a-million upper bound estimate 
of excess lifetime cancer risk, or continuous lifetime exposure levels 
associated with no significant risks of adverse non-cancer effects 
(e.g., EPA's Inhalation Reference Concentration (RfC)). As stated 
earlier, estimated concentrations greater than risk-based 
concentrations should be viewed as indicators of a potential health 
problem, and not as a characterization of health risks. While we 
recognize certain limitations associated with this initial attempt at 
modeling HAP concentrations nationwide, and its inappropriateness for 
use in drawing conclusions at small geographic scales, this modeling 
effort is useful as a national screening tool. In this analysis, we 
used the information generated by the CEP for urban areas and 
identified those HAPs for which the modeled concentrations exceeded 
risk-based concentrations in the greatest number of urban census 
tracts.
---------------------------------------------------------------------------

    \28\ See footnotes 13 and 14.
---------------------------------------------------------------------------

    We received comments on several aspects of our use of the CEP 
analysis in our method for identifying the draft urban HAPs list. Some 
commenters felt that the addition of background concentrations was 
inappropriate. Additionally, some commenters questioned the 
appropriateness of the reference values used for some HAPs. We 
recognized that the background value for one of the HAPs (bis(2-
ethylhexyl)phthalate or DEHP) was wrong, and we agreed that we should 
focus the analysis on modeled concentrations resulting from 
controllable sources. Additionally, we're currently using updated risk-
based concentrations which, in some cases, differ from those used in 
the CEP analysis. Consequently, prior to using this analysis as part of 
our final methodology, we repeated the analysis

[[Page 38719]]

for the subset of affected HAPs using the modeled concentrations 
resulting only from current area, major and mobile sources (i.e., 
without addition of a background value) and an updated set of risk-
based concentrations. We've described the details of this reanalysis in 
the technical support document in the public docket.
    d. Integration of the three analyses. In selecting the urban HAPs 
for the integrated Strategy, we compared the results of these three 
separate ranking analyses and applied the following criteria when 
integrating their results. We selected those HAPs for which a publicly 
reviewed baseline national emissions inventory was available \29\ and 
which had been either:
---------------------------------------------------------------------------

    \29\ On June 20, 1997 we published notice of a draft listing of 
source categories for regulation under section 112(c)(6) of the Act 
(62 FR 33625). As part of this notice, we requested public review 
and comment on the baseline national emissions inventory for the 
seven pollutants identified under section 112(c)(6). In the fall of 
1998, we requested and obtained public review on our baseline 
national emissions inventory for 40 HAPs, five of which had also 
been reviewed as part of the rulemaking process under section 
112(c)(6). During both of these public reviews, many comments were 
received on various aspects of the emissions information, and we 
considered these comments in making improvements to the baseline 
national emissions inventory for those HAPs. Details concerning 
these two public reviews and documentation of the resultant 
inventory information are presented in two documents (``1990 
Emissions Inventory of Section 112(c)(6) Pollutants: Final Report'' 
and ``1990 Emissions Inventory of 40 Candidate Section 112(k) 
Pollutants'') available at www.epa.gov/ttn/uatw/112c6/112c6fac.html 
and www.epa.gov/ttn/uatw/112k/112kfac.html, respectively. The public 
reviews provided us with an inventory that was appropriate for our 
use on a national scale, in the identification of the urban and area 
source HAPs. However, this baseline inventory may require certain 
modifications for small scale detailed analyses such as those 
described in section II.B.
---------------------------------------------------------------------------

     Identified by at least two of the three analyses 
(regardless of area source contribution); or
     Identified by at least one of the three analyses and 
having an area source contribution to total emissions of at least 25 
percent.
    The second criterion was set in recognition of the area source 
emphasis of this integrated Strategy. These criteria produced an 
integrated list of 33 urban HAPs.
    As discussed earlier, section 112(k)(3)(B) of the Act requires us 
to identify not less than 30 HAPs that are estimated to pose the 
greatest threat to public health in the largest number of urban areas 
as the result of emissions from area sources (``the area source 
HAPs''). To identify these 30 area source HAPs, we ranked the list of 
33 urban HAPs by percent contribution to national urban emissions from 
area sources and selected the 30 urban HAPs with the greatest area 
source contributions. The remaining three urban HAPs (i.e., coke oven 
emissions, 1,2-dibromoethane, and carbon tetrachloride) have less 
significant emissions contributions from area sources and aren't among 
the 30 area source HAPs considered in the area source category listing 
described in section II.C.
    Some commenters on the draft Strategy were concerned that the 
percent contribution to national urban emissions from area sources was 
too low for some of the HAPs on the draft area source HAPs list, thus 
not placing enough emphasis on risks from area sources. While we note 
that the percent contribution from area sources for the area source 
HAPs ranges down to as low as 2.9 percent, these values apply to total 
urban emissions nationally. In individual urban areas as well as in 
local communities within large areas, area sources may play a much 
larger role. Because the Act requires us to select not less than 30 
area source HAPs and because the percentage of emissions from area 
sources will vary, we consider this an appropriate approach to identify 
the area source HAPs on which the Strategy will focus in reducing area 
source emissions and any associated health risks in individual urban 
areas nationwide.\30\ Accordingly, this list of 30 area source HAPs was 
used in identifying the list of new area source categories for which 
standards will be addressed as required by section 112(c)(3) and 
section 112(k)(3)(B)(ii).
---------------------------------------------------------------------------

    \30\ Given the uncertainties and limitations associated with the 
information upon which the 30 area source HAPs selection was based, 
we don't believe that identifying greater than the statutory minimum 
of 30 HAPs is warranted at this time.
---------------------------------------------------------------------------

B. How does EPA Plan to Address Requirements for Area Sources of HAPs?

1. Area Source Category Selection Approach in Draft Strategy
    The Clean Air Act includes two provisions--sections 112(c)(3) and 
112(k)(3)(B)(ii)--that instruct us to identify and list source 
categories that contribute to the emissions of the 30 ``listed'' (or 
area source) HAPs, and that are, or will be, subject to standards under 
section 112 of the Act. The language in these two sections differs 
slightly. Section 112(c)(3) requires us to list, pursuant to section 
112(k)(3)(B), sufficient categories of sources ``to ensure that area 
sources representing 90 percent of the area source emissions of the 30 
[listed] hazardous air pollutants'' are subject to regulation under 
section 112. As explained in the draft Strategy, this would seem to 
allow us to regulate sources accounting for either 90 percent of the 
combined emissions of all of the 30 area source HAPs, or 90 percent of 
the emissions of each of the 30 area source HAPs. By contrast, section 
112(k)(3)(B)(ii) requires us to identify sufficient categories to 
``assure that sources accounting for 90 per centum or more of the 
aggregate emissions of each of the 30 identified hazardous air 
pollutants'' are subject to standards under section 112(d). This 
language explicitly requires us to regulate sources accounting for 90 
percent of the emissions of each of the 30 area source HAPs. As a 
result, in the draft Strategy we adopted the interpretation that 
allowed us to read the two provisions consistently, and assembled a 
draft list of area source categories representing 90 percent of the 
emissions of each of the 30 area source HAPs.
    We adopted a two-step process for selecting the source categories 
for the draft list. First we listed all of the area source categories 
already subject to area source standards. For each of these source 
categories we identified their percentage contribution to the total 
area source emissions for each of the 30 area source HAPs. We then 
listed additional area source categories as necessary, listing the 
largest contributors first, until the list of area sources represented 
90 percent of the emissions for each of the 30 area source HAPs.
2. Improvements in Area Source Category Information
    Since issuing the draft Strategy, we've significantly improved our 
emissions inventory data for many area source categories. (The final 
information on the subset of pollutants of the baseline inventory used 
in this analysis and a description of the changes made is in the 
technical support document ``Emissions Inventory of 40 Candidate 
Section 112(k) Pollutants; Supporting Data for EPA's Section 112(k) 
Regulatory Strategy'' available at www.epa.gov/ttn/uatw/112k.) The 
draft inventory for the subset of the HAPs of the baseline emission 
inventory was available twice for public review. From this extensive 
review, we received over 200 comments on the inventory, which were 
addressed where data were provided. Based on the large number of public 
comments, and information from internal comments, we've made many 
changes to the baseline emissions inventory used to identify HAP 
sources. In particular, better emission information for many of the 
sources subject to section 112(d) MACT standards made a significant 
difference in the inventory. The percent

[[Page 38720]]

contribution from major versus area sources for each source category 
was also refined and updated based on better information. For many MACT 
standards, we now have lists of regulated facilities, which allows for 
better designation of major facilities in the inventory.
    We received several comments requesting that the area source 
categories designated as ``SIC combined'' be broken down into 
individual SIC (or Standard Industrial Classification) codes. Examples 
of these source categories from the draft Strategy were Electronic and 
other Electric Equipment Manufacturing (SICs combined), Food Products 
(SICs combined) and Instruments and Related Products (SICs combined). 
The way in which the SIC codes were combined didn't reflect a technical 
analysis of whether these SIC codes could in fact be combined into 
single source categories for regulatory purposes. In general, the 
combinations included large numbers of different industry types which 
would later have to be broken down into separate projects and separate 
source categories for regulation. In addition, it was difficult to 
discern from the list which subsets of the multiple SIC codes were 
actually emitting the pollutants of concern and would eventually be 
subject to regulation.
    For the final Strategy, we listed source categories (presented in 
Table 3) that primarily represent single SIC codes in order to more 
accurately identify the sources that may ultimately be subject to 
regulation. The exception to this is when the source category was 
derived directly from information obtained during the development of a 
section 112(d) standard (e.g., Paint Stripping Operations), in which 
case the area source category described for the standard may 
incorporate multiple SIC codes.
    Despite these improvements in the baseline, there are still 
uncertainties in the emissions reported in some categories and in some 
of the TRI reporting. Our awareness of these uncertainties is based on 
our improved knowledge of some source categories and emission 
estimation methods, and also on an improved recognition of the limits 
of our data for other source categories. For the development of the 
area source category listing, we needed to use the baseline inventory 
information on a more refined scale (at the source category level) than 
we did in development of the HAPs list where we used the baseline 
inventory on a national scale. For this reason, we sometimes modified 
the individual source category information in various ways, such as by 
combining source categories' emission information. In a few cases, we 
changed the emission information related to tonnage for some source 
categories. These adjustments to tonnage didn't affect the total 
emissions used on a national scale. As a result of these changes, the 
information presented in the area source category analysis (source 
category names and tonnage) may not always match the way source 
categories are presented in the final baseline inventory.
    Examples of some changes made in the area source category analysis 
include combining all the emissions from human and animal cremation, 
because they will be addressed under one rulemaking (Other Solid Waste 
Incinerators). For the same reason, we combined all the emissions from 
institutional and commercial heating, as this will be addressed under 
one rulemaking (Institutional/Commercial Boilers). We also included the 
area emission estimates for the source category Paint Stripping 
Operations, because they were inadvertently excluded from the final 
baseline inventory. We changed the name of the source category listed 
as Chlorine Production in the baseline to Mercury Cell Chlor-Alkali 
Plants. This revised source category name better represents the portion 
of the industry which will be ``subject to standards''. Additional 
changes are described in the technical support document for identifying 
area source categories.
    As discussed in section II.A.2., several of the 30 area source HAPs 
listed in the draft Strategy have been replaced based on updated 
information. The result is the addition of the following HAPs to the 
list of 30 area source HAPs: beryllium compounds, hexachlorobenzene, 
polychlorinated biphenyls (PCBs), quinoline, vinyl chloride, and 
1,1,2,2,-tetrachloroethane. Quinoline was included in the draft 
Strategy list for major sources only, but based on updated information 
is now included for area sources. These changes in the area source HAPs 
list have also led to changes in the area source categories list.
3. Area Source Category Selection Approach in Final Strategy
    We've reviewed the provisions in sections 112(c)(3) and 
112(k)(3)(B)(ii), and believe the most reasonable interpretation of the 
Act is still the interpretation adopted in the draft Strategy. In order 
to comply with the requirements of both sections, we must list those 
source categories representing 90 percent of the emissions of each of 
the 30 area source HAPs.
    We have, however, changed our criteria for selecting the source 
categories contributing to emissions of the 30 area source HAPs. Again 
we've adopted a two-step approach with the first step being similar to 
that in the draft Strategy. In the first step we've identified area 
sources that contribute to emissions of the 30 area source HAPs, and 
that are subject to existing standards, or will be subject to standards 
that are currently being developed. These area source categories have 
already been listed for regulation under the Act. As in the draft 
Strategy, for each of these source categories we identified the percent 
contribution to the total area source emissions for each of the 30 area 
source HAPs.
    In the second step, we've decided, at this time, to add only those 
area source categories that contribute at least 15 percent of the total 
area source emissions of any of the individual area source HAPs to the 
list of source categories. We've adopted this criterion to account for 
the uncertainties in our current inventory data. While we've been able 
to significantly improve our baseline emissions inventory data, data 
gaps and uncertainty still remain. This is particularly true as we move 
to a more refined scale to determine emissions at a source category 
level. As a result, we've decided to only list new categories of area 
sources at this time if the inventory data demonstrate that each newly 
listed area source category contributes at least 15 percent to the 
national urban emissions of at least one of the 30 area source HAPs. 
Once listed, we've counted the percent contribution, even if less than 
15 percent, to emissions of any other area source HAPs, because once 
the source is subject to regulation its emissions of any of the 30 area 
source HAPs can be counted toward the 90-percent goal for each of the 
area source HAPs. Likewise, when we subject these source categories to 
regulation we'll evaluate regulation of all 188 HAPs, not just the 33 
urban HAPs listed under this Strategy.
    The result of these new criteria for the source selection process 
is that the current list doesn't, at this time, contain area source 
categories representing 90 percent of the emissions of each individual 
HAP. It's important to make clear that we still intend to meet our 
statutory obligation to list area sources accounting for 90 percent of 
the emissions of each of the 30 area source HAPs. We've chosen to 
complete this list in stages, adding to, deleting from, or shuffling 
the list as we gather more and improved data. This first stage lists 
those area source categories that contribute at least 15 percent, and,

[[Page 38721]]

therefore, we're confident add real contributions to the total area 
source emissions of a particular area source HAP. As discussed in 
section IV.D., we'll be conducting an initial national risk assessment 
in the spring of 2000 that will be used in part to prioritize which 
standards to pursue first. This initial assessment will use the much 
better-developed 1996 NTI. We'll use this information as part of our 
process to reevaluate the source categories listed in the Strategy. 
Based on this updated information, we may decide to remove an area 
source category listed here if, for example, the reason for the listing 
was inaccurate (e.g., faulty reporting to TRI) or if no urban area 
sources exist. We'll also use this assessment to evaluate area source 
categories to be added to the list.
    We believe this iterative approach is consistent with the general 
scheme for listing and regulating area sources under section 112 of the 
Act. Section 112 establishes two distinct steps for regulating 
emissions of HAPs--one for listing source categories under 112(c) and 
one for setting standards under 112(d). Section 112(k) incorporates 
this two-step approach. The source category listing step (see for 
example, sections 112(c)(1) and (9)) is intended to be an ongoing 
process. Under section 112(e)(4), listing of a particular source 
category isn't considered final agency action until EPA issues emission 
standards for that source category. Thus, we feel the list of area 
source categories is flexible both for the addition of new area source 
categories and/or removal of area source categories, through public 
notice. We believe our current approach for fulfilling the 90-percent 
requirements in sections 112(k)(3)(B) and 112(c)(3) is consistent with 
the overall structure of section 112 which authorizes us to treat the 
list of area source categories as a work in progress.
    One alternative to this iterative approach would be to attempt to 
list all sources accounting for 90 percent of the emissions of each 
individual area source HAPs as we did in the draft Strategy, and to 
make changes in the future as data are collected and improved. We 
decided against this approach because it would involve listing many 
area source categories contributing very small amounts of a particular 
HAP based on data that we consider in many instances to still have 
significant uncertainty despite numerous improvements. In the end, we 
believe the two approaches aren't meaningfully different. Even if we 
officially ``listed'' these small contributors, their status on the 
list would be tentative at best. Under the current approach, we've 
identified all of these small contributors in the supporting materials 
for this rulemaking, but we've chosen not to list them under section 
112(c)(3) at this time, if the emissions currently appear to be less 
than 15 percent of the total area source emissions of any individual 
area source HAP. Under both approaches the list will likely change with 
new and improved inventory data.
4. New Area Source Category List
    With the two-step approach described above, we identified the area 
source categories listed in Tables 2 and 3. In step one, we identified 
those area source categories that contribute to emissions of the 30 
area source HAPs, and that are subject to existing standards, or will 
be subject to standards that are currently being developed. These 
source categories are provided in Table 2. We've included Hazardous 
Waste Combustors on this list, despite the fact that information 
related to the percentage contribution from area source Hazardous Waste 
Combustors hasn't yet been completely defined, because the Hazardous 
Waste Combustor NESHAP (as proposed) would subject area sources to the 
same standards as major sources. Once we determine the percentage of 
urban area emissions from the area source categories affected by this 
rule, their emissions will be counted toward the 90-percent requirement 
for the appropriate HAPs.
    Table 3 includes those new area source categories being listed 
under section 112(c)(3) for the first time. These area source 
categories were identified in step two of our selection process, which 
identified area source categories contributing at least 15 percent of 
the total area source emissions of any of the 30 area source HAPs.

       Table 2.--Area Source Categories Already Subject to Standards or Which Will Be Subject to Standards
----------------------------------------------------------------------------------------------------------------
              Chromic acid anodizing                                     Industrial boilers
----------------------------------------------------------------------------------------------------------------
Commercial Sterilization Facilities..............  Institutional/Commercial Boilers.
Other Solid Waste Incinerators (Human/Animal       Medical Waste Incinerators.
 Cremation).
Decorative Chromium Electroplating...............  Municipal Waste Combustors.
Dry Cleaning Facilities..........................  Open Burning Scrap Tires.
Halogenated Solvent Cleaners.....................  Portland Cement.
Hard Chromium Electroplating.....................  Secondary Lead Smelting.
Hazardous Waste Combustors.......................  Stationary Internal Combustion Engines.
----------------------------------------------------------------------------------------------------------------


                                Table 3.--New Area Source Categories Being Listed
----------------------------------------------------------------------------------------------------------------
 
----------------------------------------------------------------------------------------------------------------
Cyclic Crude and Intermediate Production.....  Municipal Landfills.
Flexible Polyurethane Foam Fabrication         Oil and Natural Gas Production.
 Operations.
Hospital Sterilizers.........................  Paint Stripping Operations.
Industrial Inorganic Chemical Manufacturing..  Plastic Materials and Resins Manufacturing.
Industrial Organic Chemical Manufacturing....  Publicly Owned Treatment Works.
Mercury Cell Chlor-Alkali Plants.............  Synthetic Rubber Manufacturing.
Gasoline Distribution Stage I.
----------------------------------------------------------------------------------------------------------------


[[Page 38722]]

5. Meeting the Requirement To List Area Sources Representing 90 Percent 
of Emissions
    The current list of area source categories doesn't include 
categories representing 90 percent of the emissions of each of the 30 
area source HAPs. The current list meets the 90-percent or greater 
requirement for 11 31 of the 30 area source HAPs. For 10 
32 other HAPs, the list accounts for at least 80 percent of 
the emissions, and for ethylene dichloride the list accounts for 
approximately 78 percent of the emissions. Improved inventory data may 
demonstrate that the current list of area sources already meets the 90-
percent requirement for some of these HAPs. The remaining HAPs on the 
list represent less than 75 percent of the emissions: arsenic 
compounds, cadmium compounds, chromium compounds, hexachlorobenzene, 
lead compounds, manganese compounds, nickel compounds, and 
polychlorinated biphenyl.
---------------------------------------------------------------------------

    \31\ Including 1,1,2,2-tetrachloroethane, 1,2-dichloropropane, 
polycyclic organic matter, acetaldehyde, acrolein, benzene, dioxin, 
furans, ethylene oxide, formaldehyde, quinoline, and 
tetrachlorethylene.
    \32\ Including 1,3-butadiene, 1,3-dichloropropene, 
acrylonitrile, beryllium compounds, chloroform, hydrazine, mercury 
compounds, methylene chloride, trichloroethylene, and vinyl 
chloride.
---------------------------------------------------------------------------

    In the case of the metal compounds for arsenic, cadmium, chromium, 
lead, manganese and nickel, we know we haven't listed enough new area 
source categories to say that we've completely addressed the emissions 
from these area source HAPs. In the case of the metal HAPs, there tend 
to be numerous source categories, each contributing only a small 
percentage of the HAPs. In many cases, this is because the source 
categories have already reduced emissions due to other control programs 
in place. However, because these pollutants can have significant health 
effects, we'll be developing a separate strategy to specifically 
address emissions of these metals. As part of our initial evaluation of 
the area sources of these HAPs, we're including the following source 
categories for further evaluation (our current data indicate that each 
contributed five to twelve percent of area source emissions of one or 
more of these metal HAPs):
     Sewage Sludge Incineration.
     Aluminum Foundries (castings).
     Steel Foundries.
     Secondary Copper Smelting.
     Stainless and Nonstainless Steel Manufacturing--Electric 
Arc Furnaces (EAF).
     Iron Foundries.
     Plating and Polishing.
     Cadmium Refining and Cadmium Oxide Production.
     Autobody Refinishing Paint Shops (called Paint 
Applications in the baseline inventory).
     Pressed and Blown Glass and Glassware Manufacturing.
    We aren't listing these categories for possible regulation at this 
time; however, after further evaluation of these categories, some or 
all may be added to our area source category list.
    We haven't listed any area source categories which specifically 
contribute emissions of PCBs or hexachlorobenzene, although some of the 
source categories listed may emit one or both of these HAPs. We've 
decided to wait on listing any source categories contributing to area 
source emissions of hexachlorobenzene or PCBs, because these HAPs 
weren't included in the candidate list of HAPs for which we collected 
detailed inventory data in preparation for the Strategy; therefore the 
emissions inventory baseline for these HAPs didn't receive the same 
level of review. We've already begun efforts that may supplement our 
inventory data for these HAPs, and, as appropriate, we'll list new area 
source categories when we collect more data and make the list available 
through public notice. For example, we're currently researching the 
sources of PCBs, and whether PCBs may be the product of incomplete 
combustion. The findings of this research could significantly change 
the emissions inventory for this pollutant. Even though we're not 
listing source categories of these pollutants at this time, like the 
metals, we're concerned about the potential health effects of these 
pollutants, and we have a number of programs across EPA working to 
address them (e.g., the PBT initiative and the Binational Toxics 
Strategy).
    We anticipate evaluating the source categories for these and the 
other remaining HAPs for which we haven't reached a 90-percent emission 
reduction, including the six metal HAPs, PCBs and hexachlorobenzene, 
when we conduct the initial risk assessment in the spring of 2000 
(discussed in section IV.D.). We intend to adjust this list in the 
event that new information comes forward and will complete the list by 
2003.
6. Comments on Specific Source Category Listings
    Several comments on the draft Strategy addressed the need to add or 
delete certain source categories. Many of these comments have been 
addressed with the changes described above to the emissions inventory 
and the urban HAPs list. Many of these commenters asked that we add 
several source categories (such as dry cleaners, retail gas stations, 
print shops, autobody shops, and beauty shops). Some of these source 
categories are already addressed by area source MACT standards (e.g., 
dry cleaners). Many of the others involve organic emissions from 
consumer products such as surface coatings, metal cleaning, solvents, 
personal care products, and household cleaning products. While these 
products may be responsible for a significant fraction of the emissions 
of several of the 30 area source HAPs, we believe section 112 isn't 
necessarily the most appropriate regulatory mechanism for controlling 
them. For many of these emissions, we believe section 183(e) provides 
the more useful authority. For example, in September 1998, we published 
a VOC rule under section 183(e) for household consumer products. This 
rule will affect approximately 220 consumer product manufacturers and 
importers nationwide. At the same time we published two other national 
rules which address VOC emissions from consumer and commercial 
products: Architectural Coatings and Automobile Refinishing coatings. 
These combined rules should provide reductions of over 2.4 million tons 
of VOC per year. Automobile Refinishing is also included on our list 
for further evaluation due to metals emissions.
    Similarly, we don't believe section 112 is the most appropriate 
tool to address refueling emissions at gas stations. Instead, 
consistent with Congress' intent, we've chosen to regulate these 
emissions through sections 182(b)(3) and 202(a)(6). The ``stage II'' 
and ``onboard requirements'' programs developed under these authorities 
will lead to reductions of VOCs and HAPs of 300,000 to 400,000 tons per 
year (63 FR 17844, April 10, 1998).
    Commenters also said the list should focus on source categories 
emitting the deadliest HAPs. As we explained in section II.A., toxicity 
was one of the key criteria in all of the rankings used to develop the 
list of 30 area source HAPs. As a result, pollutants such as dioxins 
and beryllium compounds, because of their high toxicities, are included 
on the list of 30 area source HAPs, despite relatively small overall 
emissions in urban areas. Thus, toxicity is built into the list of 
source categories selected for regulation because toxicity is built 
into the list of pollutants used to select these source categories.

[[Page 38723]]

7. Additional Requirements for Area Source Categories Already Subject 
to MACT
    Several of the source categories listed today (e.g., Municipal 
Landfills, and Publicly Owned Treatment Works) are already in source 
categories covered by MACT standards for major sources. As discussed in 
section II.C.1., we'll develop area source standards for the listed 
area source categories. When it's practical during our rulemaking 
activities, we'll attempt to combine information gathering for area and 
major sources. A good example is the development of the MACT standard 
for municipal landfills. This source category is required to be 
evaluated for major sources as a MACT standard, and we've expanded our 
data base to include area sources as well. In other instances, such as 
for Publicly Owned Treatment Works, the MACT standard was already 
proposed and is near promulgation, so it isn't possible to coordinate 
rulemaking for the major and area sources at the same time.
    In the cases where standards already apply to listed area sources 
(e.g., Municipal Waste Combustors, Medical Waste Incinerators, Chromium 
Electroplating, and Halogenated Solvent Cleaning), we'll coordinate the 
need for additional regulation through assessments we'll be conducting 
under the section 112(f) residual risk program. Information on how 
we'll conduct assessments on residual risk are discussed in the 
residual risk report.\33\ We'll also be evaluating the effectiveness of 
the standards that are already in place through information provided by 
State, local and Tribal air agencies. Also, as we continue to assess 
our progress in meeting our air toxics Strategy goals, we'll reevaluate 
the need for additional area source standards to ensure that the 90-
percent requirement and our other goals are met.
---------------------------------------------------------------------------

    \33\ U.S. EPA. Residual Risk Report to Congress. EPA-453/R-99-
001. March 1999.
---------------------------------------------------------------------------

C. What Regulatory Actions Will EPA Take To Implement the Strategy?

    Consistent with our goals, we intend to assess cumulative risks to 
the public from HAP exposures resulting from stationary (area and 
major) and mobile sources. Based on the outcome of these assessments, 
we'll undertake the needed regulatory actions using the appropriate 
authorities. These actions include developing area source standards, 
which are discussed in sections II.C.1. though II.C.5. We'll also 
regulate motor vehicle and fuel HAPs as described in section II.C.6. 
Finally, we'll develop additional major source standards under section 
112(d), section 112(f), and other programs under the Act, as needed to 
reach our goals. The role of major stationary sources in the Strategy 
is discussed in more detail in section II.C.7. Our approach for 
addressing combinations of source types (e.g., at airports) is 
described in section II.C.8.
1. Our Approach to Developing Area Source Standards
    We plan to pursue a tiered approach that will consider three 
standard setting processes. The specific process selected for a 
particular source category will depend on the criteria outlined below. 
The three tiers of standard setting processes that will be considered 
are:
     Tier 1--MACT standard process;
     Tier 2--Source category specific GACT standard process; 
and
     Tier 3--Flexible GACT process.
    We received a number of comments on the draft Strategy stating that 
our regulatory intentions for area sources were unclear. In addition, 
we received comments requesting flexibility for State/local/Tribal 
governments and for emission sources in implementing these area source 
standards. The following discussion attempts to provide the needed 
clarifications and to explain our approach to developing a flexible 
regulatory development process.
    Tier 1--MACT standards. We'll develop MACT standards in accordance 
with the process outlined in section 112(d)(3) for those area sources 
whose emissions pose the greatest threat to human health and the 
environment and for which the technology to achieve maximum reductions 
in HAP emissions is appropriate. Section 112(d)(3) requires the 
standards to reduce HAP emissions as much as is achievable, considering 
the cost of these reductions, effects on health or the environment 
(other than air), and energy requirements.
    Section 112(d)(3) requires us to use a minimum statutory baseline 
(``floor'') when setting MACT standards. For new sources, the MACT 
standards for a source category or subcategory must be at least as 
stringent as the emission control achieved in practice by the best 
controlled similar source. The standards for existing sources can be 
less stringent than standards for new sources, but they can't be less 
stringent than the average emission limitation achieved by the best-
performing 12 percent of existing sources (excluding certain sources) 
for categories or subcategories with 30 or more sources, or by the 
best-performing 5 sources for categories or subcategories with fewer 
than 30 sources.
    We've issued MACT standards for area sources in previous cases. For 
example, in the chromium electroplating national emission standards for 
hazardous air pollutants (NESHAP), we developed MACT standards for area 
sources because of the high toxicity of chromium. Similarly, in the 
Portland Cement NESHAP, we determined that MACT controls were 
appropriate because of the quantity and toxicity of the HAPs being 
emitted from area sources. In addition, both of these source categories 
have numerous, widespread sources.
    Tier 2--Source category specific GACT standards. While we may 
develop MACT standards for some area sources, we expect most sources 
will be subject to GACT standards developed in accordance with section 
112(d)(5). As with MACT standards, GACT standards would be developed 
for a specific source category, but they would be based on the use of 
GACT as opposed to the use of MACT. This approach will be used to 
address source categories that present a human health risk or 
environmental concern, but where GACT is a more appropriate approach 
for reducing HAP emissions than MACT. To make these standard-setting 
decisions, we'll consider economic feasibility and other factors that 
could lead us to GACT.
    Tier 3--Flexible GACT process.
    Considering the large number and diversity of area sources and 
limitations in the data and information currently available for many of 
them, we expect it may be appropriate in some cases to develop flexible 
requirements that would apply to several area source categories where 
more flexibility is appropriate (e.g., where there are very few area 
sources, they are confined to a limited geographic area or areas, or 
they contribute to localized public health or environmental risks). 
Under this option, we might develop general requirements such as a 
process rule similar to section 112(g), which would be applicable to 
area sources in several source categories. These general requirements 
could outline procedures for determining what constitutes ``generally 
available control technology'' in this context. By following these 
procedures, States, local governments, and Tribal agencies could elect 
to develop GACT for the area sources. We'd review the resulting 
standards to ensure they were developed following the procedures 
contained within the general requirements and, if appropriate, we'd 
adopt the standards as GACT for these area sources.
    We believe this approach presents several advantages. It could be 
implemented in a manner that permits State, local and Tribal agencies 
to

[[Page 38724]]

address cumulative risk posed by exposures to HAP emissions from many 
different source categories. It also permits greater flexibility in 
tailoring GACT to individual area sources or area source categories 
which may contribute to an undue public health risk in a particular 
area. For example, a State, local or Tribal agency could tailor GACT to 
a particular source by requiring potentially more stringent controls 
when the source contributes emissions that, when aggregated with 
emissions from other sources in the area, pose health risk concerns. 
They could also require less stringent controls when the source is in 
an area where exposures to aggregated emissions don't present 
significant concern.
    To supplement our general requirements, we may choose to issue 
control technique guidelines or alternative control technology 
documents to provide information on generally available control 
technologies for controlling HAP emissions.
2. The Legal Basis for Using GACT for Area Source Categories
    Section 112(k)(3)(B)(ii) directs us to assure that the listed area 
sources are subject to standards under section 112(d), which includes 
two levels of standards--``maximum achievable control technology'' 
(MACT) and ``generally available control technology'' (GACT). We read 
the requirement in section 112(k)(3)(B)(ii) to give us flexibility in 
deciding which level of control to apply to a given source category.
    Unlike MACT, which is specifically described in sections 112(d)(2) 
and (3), the meaning of GACT, or of what is ``generally available,'' is 
not defined in the Act. Section 112(d)(5) authorizes the Administrator 
to:

    [P]romulgate standards or requirements applicable to [area] 
sources * * * which provide for the use of generally available 
control technologies or management practices by such sources to 
reduce emissions of hazardous air pollutants.

    Section 112(d)(5) thus doesn't limit us to strict ``standard 
setting'' in order to provide for the use of GACT. We read section 
112(d)(5) to authorize promulgation of at least two types of rules: 
rules that set emission levels based on specific controls or management 
practices (analogous to MACT standard setting), and rules that 
establish permitting or other regulatory processes that result in the 
identification and application of GACT. As long as the result of the 
section 112(d)(5) rulemaking is that sources use enforceable generally 
available control technologies or management practices, section 
112(d)(5) appears to give us flexibility in choosing between the 
adoption of numerical emission limits and the promulgation of other 
requirements that result in sources applying GACT.
    As discussed previously, we intend to determine which of these 
regulatory approaches is most appropriate when we conduct rulemaking on 
the individual source categories. However, it's important to bear in 
mind that we retain authority under section 112(d) to regulate any 
listed area sources more stringently, under MACT, where appropriate, to 
effectively address risk. In addition, we can lower the emission 
thresholds for defining sources as ``major'' and, therefore, subject 
what would have otherwise been area sources to major source 
requirements (MACT).
3. Issues on the National vs. Local Scope of Area Source Standards
    Section 112(k) requires that listed area source categories be 
subject to standards under section 112(d).
    Many commenters on the draft Strategy addressed the implications of 
selecting a national versus a local scope for the area source 
standards. Some said national area source standards are unfair and 
inefficient, because they apply to sources located outside of urban 
areas where they may pose less risk. However, others said failing to 
apply the standards nationally creates an unlevel playing field for 
businesses in urban areas, encourages urban sprawl, and creates a 
disincentive for new businesses in brownfield and urban development 
areas.
    As indicated by our initiatives on urban development and brownfield 
redevelopment, we share the concern of many commenters that applying 
standards only in the urban areas could negatively impact economic 
opportunities in the urban areas and could, in some cases, encourage 
urban sprawl. In addition, we're also concerned about the 
disproportionate public health risk for people, particularly sensitive 
populations such as children, in smaller cities or rural areas that 
might be located near area sources. However, we're aware that for some 
area source categories it may be more practical and appropriate to 
limit the applicability to urban areas. Thus, our expectations are to 
apply area source standards under section 112(k) nationally; however, 
for each individual area source category, we'll determine whether it's 
more appropriate for area source standards to apply nationally or only 
in urban areas.
    For those area source categories where the standards only apply in 
urban areas, we'll look to the consolidated metropolitan statistical 
area (C/MSA) boundaries as a starting point to define the urban area. 
Although we used the urban 1 and urban 2 definitions \34\ for the 
development of the inventory to support the HAPs and source category 
analysis, we believe the C/MSAs are more appropriate for defining 
applicability of area source standards because the C/MSAs better 
reflect the nature of population density, commercial development, area 
growth, and air emissions that represent urban areas.
---------------------------------------------------------------------------

    \34\ Urban 1 areas are those counties that have a population of 
more than 250,000. Urban 2 areas are counties where at least 50 
percent of the population is considered to be urban.
---------------------------------------------------------------------------

    Although we generally believe that urban areas are those C/MSAs 
with populations of more than 50,000, we recognize that the appropriate 
area in which standards should apply may vary among area source 
categories. Consequently, we believe the determination of the area in 
which standards will apply should be made separately for each source 
category.
4. Title V Permits for Area Sources
    Under section 502(a) of the Act, area sources can be exempted from 
Title V permitting if the Administrator determines that compliance with 
Title V requirements is impracticable, infeasible, or unnecessarily 
burdensome for the area sources in question. As specified in 40 CFR 
63.1(c)(2), 70.3(b)(2) and 71.3(b)(2), individual standards promulgated 
under part 63 will specify whether Title V permits are required for 
area sources. Consequently, we'll determine in each subpart that is 
developed for the Strategy whether area sources affected by the subpart 
are subject to, or exempt from, Title V permitting.
    Factors that might influence this determination were raised by 
commenters. For example, many commenters felt that area sources are 
often small businesses, and that requiring Title V permits for these 
sources places an unfair resource burden on them. Other commenters felt 
that these sources should be covered by Title V permits in order to 
provide resources to the States through the collection of Title V fees, 
and to provide an opportunity for community input on the establishment 
of area source requirements. Title V, which is implemented through 
regulations codified in 40 CFR parts 70 and 71, generally requires 
owners or operators of area sources subject to section 112 standards to 
obtain Title V permits.

[[Page 38725]]

    We also received a number of comments in regard to Title V fees and 
the Strategy. Some commenters requested that area sources subject to 
the Title V program be charged an annual fee, rather than a per ton 
fee. How Title V fees are assessed is determined by the individual 
permitting authority and is subject to approval by EPA as part of the 
permitting authority's Title V program submittal to the Agency. 
Permitting authorities are free to assess fees based on criteria other 
than emissions, including application fees or service-based fees. 
Moreover, permitting authorities can assess fees differently among 
Title V sources. Therefore, we don't have the authority under section 
112(k) of the Act to establish a new basis for assessing Title V fees.
    Other commenters requested that Title V fees be used to fund state 
toxics reduction programs. We must emphasize that, according to 40 CFR 
70.9(a), Title V fees are to be used solely to fund a permitting 
authority's Title V program and not non-Title V activities.
5. Schedule for Area Source Standards
    We've revised the time line we presented in the draft Strategy for 
area source standards development. We believe the following milestones 
reflect a more realistic estimate of the average 4 years it takes to 
develop MACT/GACT standards. We intend to address the source categories 
newly listed here by 2004, and address additional source categories 
listed later in the process of implementing the Strategy in later years 
(i.e., 2006-2009).
     2004--promulgate the area source standards newly listed in 
today's Strategy. We'll attempt to meet this demanding schedule as 
expeditiously as practicable.
     2006--promulgate additional area source standards to meet 
the 90-percent requirement.
     2009--promulgate all remaining area source standards 
necessary to meet the 90-percent requirement.
     2012--expected compliance under all standards.
    We'll prioritize the order in which we regulate source categories 
to address those posing the greatest risks first. This will be a part 
of our initial assessments, which will be done in the spring of 2000. 
We'll be developing standards between now and 2009. Compliance with 
these standards is required within 3 years of promulgation. Therefore, 
compliance with all standards is anticipated by no later than 2012.
6. Our Approach for Mobile Source Hazardous Air Toxic Controls
    Title II of the Act provides several mechanisms to achieve 
reductions in hazardous air pollutants from mobile sources. The most 
direct of these is section 202(l) which requires us to identify the 
need for and consider regulations for control of HAPs from motor 
vehicles and their fuels.
    Pursuant to section 202(l)(1) of the Act, we released the ``Motor 
Vehicle-Related Air Toxics Study'' in 1993.\35\ This study summarized 
information on emissions of toxic air pollutants associated with motor 
vehicles and motor vehicle fuels, as well as estimated exposures, and 
potential risks. The study also provided cancer risk estimates for 
several air toxics for different years under various control scenarios. 
We've recently completed draft analyses to update the emissions and 
exposure analyses done for this study to account for new 
information.\36,\ \37\ These draft analyses include base scenarios for 
1990, 1996, 2007, and 2020, and control scenarios in 2007 and 2020. We 
modeled toxic emissions and exposure for the following urban areas: 
Chicago, Denver, Houston, Minneapolis, New York, Philadelphia, Phoenix, 
Spokane, and St. Louis. We assessed emissions and exposure from 
benzene, formaldehyde, acetaldehyde, 1,3-butadiene, and diesel 
particulate. Experts and stakeholders are currently reviewing the 
methodologies and assumptions used in the analyses, and work is on-
going to extend and revise the analyses.
---------------------------------------------------------------------------

    \35\ Motor Vehicle-Related Air Toxics Study, U.S. Environmental 
Protection Agency, Office of Mobile Sources, Ann Arbor, MI, EPA 
Report No. EPA 420-R-93-005, April 1993.
    \36\ Estimation of Motor Vehicle Toxic Emissions and Exposure in 
Selected Urban Areas. Prepared by Sierra Research, Inc., Radian 
International Corp., and Energy & Environmental Analysis, Inc. for 
U.S. EPA, Office of Mobile Sources, Assessment and Modeling 
Division, Ann Arbor, MI, Report No. EPA420-D-99-002, March 1999.
    \37\ Sierra Research, Inc. ``On-Road Motor Vehicle National 
Toxics Exposure Estimates''. Memorandum from Philip Heirigs to Rich 
Cook, U.S. EPA. October 15, 1998.
---------------------------------------------------------------------------

    As mentioned before, diesel particulate matter (PM), which is 
emitted primarily by mobile sources, isn't included on the section 
112(b) list of 188 HAP, and, as a result, isn't included on the urban 
HAP list. However, we're currently investigating the health risks 
associated with diesel PM and assessing its role in the urban air 
toxics problem. We're concerned about the potential health risks 
associated with exposures to the emissions of this pollutant mixture.
    Diesel PM is a complex pollutant mixture that is emitted primarily 
by mobile sources. Heavy-duty highway and nonroad diesel engines are 
the largest sources of diesel PM, with the total on-road and non-road 
diesel PM emissions for 1997 being 516,373 thousand tons.\38\ While 
diesel engines are used in a relatively small number of cars and light-
duty trucks today, vehicle and engine manufacturers are developing new 
engine models that may be used in an increasing share of the light-duty 
fleet, particularly light-duty trucks. If sales of car and light trucks 
with diesel engines increase substantially over time, the potential 
health risks from diesel PM could also increase substantially.
---------------------------------------------------------------------------

    \38\ EPA National Air Pollutant Emissions Trends Update, 1970-
1997. December 1998, EPA-454/E-98-007. This number also represents 
PM10 emissions, while PM-2.5 emissions are approximately 474 million 
tons. Non-road emissions include locomotives, and the on-road 
calculation excludes tire and brake wear.
---------------------------------------------------------------------------

    Diesel PM typically consists of a solid core, composed mainly of 
elemental carbon, which has a coating of various organic and inorganic 
compounds. The characteristically small particle size increases the 
likelihood that the particles and the attached compounds will reach and 
lodge in the deepest and more sensitive areas of the human lung. Both 
the diesel particle and the attached compounds may be influential in 
contributing to a potential for human health hazard from long term 
exposure.
    Section 202(l)(2) of the Act directs us to set standards to control 
HAPs from motor vehicles, their fuels, or both. Those standards are to 
be set based on available technology, taking existing standards, costs, 
noise, energy and safety factors into account. The Act also specifies 
that, at minimum, benzene and formaldehyde emissions must be addressed. 
We're currently working on a proposal in compliance with section 
202(l)(2).
    In developing the section 202(l)(2) proposal, we'll draw on the 
1993 study, and more recent analyses when completed, to describe the 
magnitude of exposure and potential health risk to the public from 
toxic emissions from motor vehicles and their fuels. We'll examine 
exposure and potential risk in a number of urban areas, as well as on a 
nationwide basis. With regard to control strategies, several of the 
existing emission control programs developed under section 202(a) 
(motor vehicle

[[Page 38726]]

controls) and section 211 (fuel controls) of the Act already limit many 
HAP emissions from motor vehicles and their fuels. We'll consider these 
programs, as well as our on-going regulatory activities (such as our 
recent proposal for new light-duty ``Tier 2'' emission standards and 
gasoline sulfur controls and our recent Advanced Notice of Proposed 
Rulemaking for diesel fuel control), in our assessment of whether 
additional controls are appropriate under section 202(l)(2).
    In addition to fulfilling the requirement to examine emissions and 
health risks from motor vehicles and their fuels, we'll continue our 
efforts to ensure coordinated use of our standard-setting authorities 
to address priority risks from mobile sources. In particular, as we 
review existing regulations for a number of motor vehicle and nonroad 
engine categories, the goal of reducing air toxics risks will be 
considered. In addition, we envision that work done in the early stages 
of implementing the Strategy, such as improving monitoring and 
inventories, will help us compare options related to the various 
emissions sources in urban areas and control authorities to provide the 
best relative reduction of risk to the urban public.
7. Role Major Stationary Sources Play in the Strategy
    As discussed in section I.C., section 112(k)(3)(B) requires that we 
ensure that area sources accounting for 90 percent of the aggregate 
emissions of each of the 30 area source HAPs are subject to standards. 
However, in achieving required reductions in cancer incidences, section 
112(k)(3)(C) permits us to consider reductions in public health risks 
resulting from actions to reduce emissions from ``all stationary 
sources and resulting from measures implemented by the Administrator or 
by the States under this or other laws.'' Therefore, we'll consider 
emission reductions from a combination of major and area sources in 
conducting risk assessments to address this requirement.
    These assessments will support regulatory efforts under the Clean 
Air Act and other authorities, as necessary, to address the identified 
risk. For example, any reductions resulting from MACT, the national 
ambient air quality standards, and other programs that achieve 
reductions in HAPs can be included in the assessment of reductions in 
risks. Therefore, if we determine that a source category or an 
individual source is presenting a significant health risk, then we'll 
address it using the appropriate regulatory authority. For example, if 
needed to provide an ample margin of safety to protect human health, 
section 112(f) residual risk standards will be developed for source 
categories currently subject to MACT. Additionally, if our analyses 
reveal a major source category that is currently unregulated or 
unlisted, but poses a public health risk, we'll list that source 
category under the authority of section 112(c) and develop the 
necessary regulations under section 112(d), or we may address it 
through other activities like pollution prevention or voluntary 
programs. Similarly, if a specific source is contributing to a local 
risk problem, then the State, local or Tribal program may be more 
appropriate for addressing that risk.
8. Our Approach for Combinations of Sources
    We also intend to coordinate our authorities in addressing 
cumulative risks posed by exposures to aggregate emissions from 
multiple source types. For example, many commenters raised concerns 
about the risks from airports to the communities that surround them. 
Airports can be viewed as mini-cities, which produce numerous 
pollutants from multiple sources and are governed by many different 
authorities. We'll need to have an integrated strategy to reduce air 
emissions and the many other environmental impacts associated with 
aviation activities.
    Although airports don't meet the definition of ``area'' or 
``major'' source under section 112 of the Act, we're involved with 
numerous efforts to better understand and reduce the environmental 
impacts of aviation-related activities and their associated human 
health risks. For example, we co-chair the EPA/Federal Aviation 
Administration Voluntary Aircraft Emissions Reduction Initiative, a 
multi-stakeholder process designed to identify and evaluate technically 
feasible and cost-effective voluntary measures to reduce aviation 
emissions. We're also participating with other stakeholders in the 
development of the South Coast Ground Service Equipment memorandum of 
understanding (MOU) in California to identify ways to achieve 
additional emissions reductions from the commercial aviation community. 
Implementation of the MOU, which should be finalized in the summer of 
1999, should yield emission reductions through increased use of cleaner 
engines, electrification, and alternative fuels. In addition, we're 
developing a Green Airport Initiative to demonstrate innovative 
strategies for reducing the environmental impacts of aviation-related 
activities at an airport undergoing expansion. In April 1999, we 
released a report that assesses the current and potential impact of 
aircraft emissions on local air quality at ten selected airports. \39\ 
The regulatory and voluntary actions underway for aviation will produce 
data that can inform this Strategy and begin to address the 
environmental impacts of aviation-related activities and their 
associated risks to the communities that surround them.
---------------------------------------------------------------------------

    \39\ ``Evaluation of Air Pollutant Emissions from Subsonic 
Commercial Jet Aircraft,'' U.S. EPA, April 1999.
---------------------------------------------------------------------------

D. How do the Various Federal Authorities Help EPA Implement the 
Strategy?

    We've already made progress in addressing air toxics emissions 
using existing programs. To put the problem in perspective, we estimate 
that approximately 8.1 million tons of 188 HAPs were released in the 
United States in 1993.\40\ We've already issued at least 43 MACT and 
GACT standards and two section 129 standards with post-1993 compliance 
dates, which will address these emissions. Emission controls for the 
nation's cars, trucks and off-road equipment, and standards for fuels 
add even more to these reductions. In this section, we'll discuss the 
utility of these programs and others to achieve additional air toxics 
emissions reductions.
---------------------------------------------------------------------------

    \40\ ``Latest Finding on the National Air Quality: 1997 Status 
and Trends,'' December 1998.
---------------------------------------------------------------------------

Federal Regulatory Activities--Clean Air Act Section 112 Authorities
    Section 112 of the Act provides several authorities for us to use 
in meeting our air toxics goals. We've promulgated section 112(d) MACT 
and GACT standards that are projected to reduce air toxics emissions by 
approximately 1 million tons per year once fully implemented. Within 
the next 10 years, as we complete more MACT and GACT standards, the air 
toxics program is estimated to reduce emissions of toxic air pollutants 
by well over 1.5 million tons per year.\41\ These nationwide emission 
reductions will contribute significantly to reductions needed in urban 
areas.
---------------------------------------------------------------------------

    \41\ See footnote 40.
---------------------------------------------------------------------------

    The need for section 112(f) standards, or ``residual risk'' 
standards, is under consideration for some of the early source 
categories covered by MACT standards. Where justified, these standards 
will address remaining public health and environmental impacts of HAPs 
to ensure an ample margin of safety to protect public health and, in 
consideration of other factors, to prevent adverse environmental 
effects.

[[Page 38727]]

Consistent with the requirements of the Act, we'll evaluate the need 
for residual risk standards for those area source categories covered by 
MACT standards, and will consider such evaluation for those area source 
categories for which GACT standards have been promulgated.
    The chemical accident prevention regulations (``Risk Management 
Program requirements'' or ``RMP rule''), were promulgated under section 
112(r). These regulations require owners and operators handling more 
than a threshold quantity of any substance listed in 40 CFR 68.130 in a 
process, to develop risk management plans to prevent and address 
accidental releases. Eighteen of these listed substances are HAPs. By 
preventing accidental releases, the RMP rule will help reduce or 
prevent emissions of these HAPs in the future.
    We've already received several requests for permits under the 
section 112(g) construction and reconstruction rule. This rule applies 
to new or reconstructed major sources and requires them to install MACT 
to reduce HAP emissions. In addition, the section 112(i)(5) rule (early 
reductions) provides incentives for sources to reduce emissions by up 
to 95 percent from 1990 levels prior to proposal of MACT for that 
source category. Approximately 27 Title V permit applications have been 
received, representing HAP reductions of over 6,800 tons.
Other CAA Authorities
    Other programs under the Act also contribute to the reduction of 
HAPs in urban areas. For example, section 109 requires States to 
develop State implementation plans to attain compliance with the 
national ambient air quality standards (NAAQS). Many of the activities 
that are designed to address criteria pollutants (e.g., ozone, 
particulate matter and lead) and attain the NAAQS also achieve 
reductions in air toxics. For example, many of the VOCs that form ozone 
are also air toxics, such as benzene and 1,3-butadiene. In addition, 
some VOCs can react in the atmosphere to form HAPs such as 
formaldehyde. Thus, controlling VOCs leads to reductions in air toxics. 
Similarly, compliance with the PM standards will provide incidental, 
but potentially significant, reductions in HAPs that are either emitted 
in the form of particulate matter or that condense to form particles in 
the atmosphere. These include polycyclic organic matter (POM), 
chromium, mercury, and other metals. In addition, lead is a criteria 
pollutant and lead compounds are listed as a HAP, so reducing lead 
emissions through the lead NAAQS also reduces HAPs.
    With regard to mobile sources, in addition to authority under 
section 202(1) to address hazardous air toxics, other sections of Title 
II that address mobile sources, including other parts of section 202 
(motor vehicles), section 211 (fuel requirements), section 213 
(emission standards for nonroad engines and vehicles), and section 219 
(urban bus standards), are resulting in reductions in urban air toxics 
by limiting VOCs, oxides of nitrogen, and particulate matter.
    We've established section 129 performance standards for two source 
categories for combustion sources. These are expected to result in over 
50,000 tons per year in HAP reductions, much of which may be in urban 
areas. Finally, actions taken under Title IV, the acid rain program, 
and Title VI, stratospheric ozone layer protection, also reduce or 
eliminate certain urban air toxic emissions.
Other Federal Laws
    There are a number of other authorities, laws, rules, and programs 
that will also help reduce emissions of HAPs and consequent exposures 
and risks. We're evaluating the appropriateness of these statutes for 
controlling emissions of HAPs as described under section 112(k)(3) and 
intend to take further actions under these statutes as appropriate. The 
contribution of other Federal programs to achieving the goals of the 
strategy is discussed in more detail in Appendix A. Following is a list 
of some relevant programs:
     Superfund Amendments and Reauthorization Act (SARA) Title 
IV.
     Toxic Substances Control Act (TSCA).
     Resource Conservation and Recovery Act (RCRA).
     Comprehensive Environmental Response, Compensation and 
Liability Act (CERCLA).
     Clean Water Act (CWA).
     Federal Insecticide, Fungicide and Rodenticide Act 
(FIFRA).
     Emergency Planning and Community Right-To-Know Act (EPCRA) 
of 1986, especially Toxics Release Inventory requirements.
     Pollution Prevention Act (PPA) of 1990.
     Oil Pollution Act of 1990.

III. State, Local and Tribal Activities

A. Why are State, Local and Tribal Programs Integral to the Process?

    The Act requires that the Strategy achieve the risk reduction goals 
considering control of emissions of HAPs from all stationary sources, 
using measures implemented by us under the Clean Air Act or other laws 
or by the States. In addition, section 112(k)(4) requires us to 
encourage State and local programs. By providing for State reductions 
in achieving the goals, Congress acknowledged that there are many State 
programs achieving HAP emissions reductions and, therefore, reducing 
the chance for exposure and health risks, including cancer. For 
example, before the Act was amended in 1990, many State, local and 
Tribal governments developed their own programs for the control of air 
toxics from stationary sources. Some of these programs have now been in 
place for many years and, for some of the source categories, they may 
have succeeded in reducing air toxics emissions to levels at or below 
those required by the Federal standards. It's clear that Congress 
intended State and local governments to be important partners in 
carrying out the mandates of the Federal air toxics program, and this 
Strategy provides a mechanism to recognize the reductions made by them.
    Because of the varied nature of the emissions sources, legislative 
structures, and other factors, the State, local and Tribal government 
programs address air toxics in a number of ways. For example, some 
programs have enacted technology standards for source categories that 
require controls for specific HAPs, much like the MACT program. Other 
programs apply a risk standard that prohibits emissions that result in 
exceedances of a certain level of risk, or they use an ambient air 
standard for air toxics that is based on threshold or exposure levels. 
Still others may rely on reductions achieved through volatile organic 
compound, particulate matter, or lead regulations developed under 
section 110 or subpart D of the Act to meet national ambient air 
quality standards. Regardless of the approaches used to address air 
toxics, State, local and Tribal governments have accomplished and 
continue to accomplish reductions in HAPs. As we proceed to implement 
the Strategy, we'll work with these governments to better characterize 
these reductions in emissions and the resulting reductions of public 
health risks, including risk of cancer.
    Developing the Strategy is a challenge at the national level 
because urban air toxics problems vary significantly across the 
country. Because of this variability, the Strategy works best if 
approached as a partnership between EPA and State, local and Tribal 
governments. These governments (including municipal

[[Page 38728]]

offices other than pollution control departments) have the most 
experience with local air pollution issues, and can lend their 
expertise and knowledge to address and resolve air toxics concerns that 
are unique to cities. Many of these governments also have existing air 
pollution control programs that currently address, and can effectively 
continue to address, some or all of these issues. In addition, these 
governments are often able to act much more quickly than we can to 
address local concerns, which leads to less overall pollution, 
particularly in the areas where pollution is of greatest concern.
    At the Federal level, we can contribute Federal standards and 
requirements using our authorities to develop and implement a national 
regulatory program. We also have the resources and expertise to 
evaluate, or to help other agencies evaluate, toxic pollution problems. 
By integrating our relative strengths, we can provide a stronger, more 
efficient, and more effective program to address toxic air pollution in 
urban areas.

B. What Are the Objectives of State, Local and Tribal Activities?

    The Strategy will be a partnership between EPA and State, local and 
Tribal governments to address the risks from air toxics in urban areas. 
Section I.C. of this document describes the goals of the Strategy. 
Listed below are the objectives that we've identified to guide the 
actions taken by us and our governmental partners, so that those 
actions will be effective and efficient in achieving the goals of the 
Strategy:
     Establish appropriate Federal measures, through guidance, 
policies, and rulemaking, which enable State, local and Tribal agencies 
to be full partners. Many of the State, local and Tribal agencies may 
be unable to do more than the Federal laws and rules require. These 
agencies could benefit from Federal rulemaking guidance in addressing 
local issues. At the same time, we recognize the need for flexibility 
for these agencies to identify and address the local issues. We need 
State, local and Tribal agencies' help to reach the Act's goals for 
healthy air, and they'll benefit by being able to tailor the Strategy 
to their specific needs.
     Provide flexibility for strong State, local and Tribal 
programs. Many of these governments have developed their own air 
programs. In fact, we received many comments requesting that the 
Strategy acknowledge programs that are already in place. Those 
governments that have been pro-active in controlling air toxics can 
benefit by tailoring the Strategy to their own needs, or by being able 
to implement a program earlier than we can.
     Provide incentives for State, local and Tribal action. 
Since enabling through standards, policies and guidance and providing 
flexibility can result in more effective and earlier controls of urban 
HAPs, it will be beneficial to State, local, and Tribal governments, to 
us, and to the public to facilitate State, local and Tribal actions.
     Set priorities among urban areas and source categories. 
Given the broad scope of the Strategy and the time it may take to 
implement, it may be most effective to first identify and address those 
areas and sources with the highest air toxic emissions or exposure 
levels (including consideration of multipathway exposure where 
appropriate).
     Provide information to the public on HAPs and potential 
risk in urban areas. The public benefits by having a sound basis to use 
in setting their pollution control priorities and communicating their 
priorities to us. Providing information to the public is also our 
responsibility, and an informed public will be better equipped to help 
us set priorities for appropriate State, local and Tribal HAP control 
actions. This public outreach will include not only information on 
exposure to air toxics, but also information on the link between water 
quality and the deposition of air toxics.
     Facilitate a focus on areas with disproportionate impacts 
and greatest risks. The Strategy is intended to recognize the potential 
for disproportionate impacts of air toxics hazards across urban areas. 
State, local and Tribal governments can be particularly effective in 
identifying and addressing disproportionate impacts of HAPs. We'll work 
with our regulatory partners to provide technical and policy guidance 
to help identify and address disproportionate impacts from HAPs, 
including consideration of multipathway exposure as appropriate.

C. What Were Comments on the State/Local/Tribal Programs and How Are 
They Being Addressed in the Strategy Development?

    Commenters expressed a general desire for more information on the 
State/local/Tribal agencies' roles and responsibilities in the 
development and implementation of the Strategy. The nature of the 
discussion in this part of the Strategy is general because our efforts 
to develop urban air toxics strategies with State, local, and Tribal 
governments are in an early stage of development. As described in a 
later section, we plan to conduct assessments to better understand our 
status with regard to the goals of the Strategy. We intend to use this 
information and also gather more input from relevant parties in the 
development of those programs through stakeholder meetings.
    Commenters had a wide variety of opinions beyond a general desire 
for more information. Some State, local or Tribal governments have 
well-developed programs and ample resources for both the scientific and 
regulatory aspects of an air program, while many others have less 
experience and/or inadequate resources and don't do more than the 
Federal government requires. As a result, some States believe that 
their programs are mature enough to be given the flexibility to 
identify HAPs and source categories to address the section 112(k) 
requirements for themselves, and they and large industries located in 
these States requested local flexibility. Other regulatory agencies, 
small businesses and public health/environmental advocacy groups 
recommended against such flexibility and requested national Federally-
mandated programs with Federal enforceability. We believe there are 
valid points from all sides. Those wanting flexibility note that risk 
reductions tailored to the local situation can be more effective than 
national solutions and that this approach takes advantage of work they 
already have in progress. Those wanting Federally-imposed programs note 
that without such Federal mandates, the playing field wouldn't be level 
for small businesses across different areas. In addition, some State, 
local or Tribal programs wouldn't be able to address urban air toxics 
without a Federal requirement. We will convene stakeholder meetings 
early in the next fiscal year to resolve these issues on State, local 
and Tribal programs. This time frame will allow for consideration of 
information from our national assessment. We plan to bring stakeholders 
together regularly for approximately six months and then take their 
input, along with comments already received on the Strategy, to develop 
a plan for implementing the State program. We intend to release this 
plan no later than six months after the end of the stakeholder 
meetings.

D. How Can State, Local or Tribal Agencies Participate in the Strategy?

    The Strategy needs to be a partnership between EPA and State, local 
and Tribal agencies in order to focus on local urban air toxics 
concerns. But our relative roles may vary according to the needs of 
particular urban areas and any limitations faced by State, local and 
Tribal governments. With our regulatory

[[Page 38729]]

partners, we'll discuss and explore options for how the State, local 
and Tribal agencies should participate in developing and implementing 
the Strategy to address public and other environmental issues related 
to air toxics.
    We see a broad range of possibilities for State, local and Tribal 
agency participation. For example, as indicated above, many regulatory 
agency programs are designed to implement delegated Federal 
requirements. However to provide additional flexibility, we may be able 
to provide a Federal program that allows the agencies to either develop 
and substitute their own requirements for an existing Federal program, 
or, if they wish, to simply adopt and implement a risk reduction 
program designed by us. For example, we could promulgate a Federal rule 
describing how we'd develop and implement a local risk reduction 
program. State, local or Tribal agencies could then either develop and 
implement a program modeled on ours, or submit an alternative program 
for our approval.
    Alternatively, instead of promulgating a Federal rule setting out 
the details of an acceptable risk reduction program, we could 
promulgate a set of minimum elements that any local risk reduction 
program--whether implemented by us or a State, local or Tribal agency--
must contain. This would provide agencies with more flexibility to 
design and implement their own risk reduction programs that we could 
approve.
    The Federal role in developing additional risk reduction strategies 
for urban areas could be smaller still. It may not be necessary for us 
to directly guide development of State, local and Tribal programs. It 
may be enough for us to encourage them to meet the goals of the 
Strategy, and to provide necessary guidance. In the end, we (or the 
State, local or Tribal agency) would still need to measure progress 
against the mandatory goals of the Act. We might then need to determine 
whether additional Federal action is warranted to meet the goals.
    In evaluating and comparing the options we develop together, we and 
our regulatory partners and other stakeholders will need to consider 
how well each option addresses the objectives described in section 
III.B. We'll also need to consider such other issues as practicality of 
implementation, resource burden at each governmental level, and 
possible adverse impacts on other Federal, State, local or Tribal 
programs.

E. What Elements Should a State, Local or Tribal Program Contain?

    No matter who develops and implements State, local or Tribal 
programs, they should contain certain basic elements to allow them to 
meet the risk reduction goals of the Strategy. For example, the 
following list of elements should be considered:
     Locally-focused assessment using existing information and 
sufficiently refined tools to identify significant contributors to 
urban risk, problem chemicals and sources, geographic ``hot spots'' 
within an urban area, and characteristics of at-risk populations.
     A process, regulatory or otherwise, to develop strategies 
aimed at reducing risk from those sources.
     Opportunity for public review of both the baseline 
assessment and the proposed risk reduction strategies.
     A process and schedule for implementing the risk reduction 
strategies.
     Evaluation of whether the goals of the Strategy have been 
met.
     Provisions to implement additional risk reduction 
strategies if the goals have not been met.
     A process to encourage public participation.
    At this point, this list is fairly general, because we don't have 
enough information to more fully develop this program structure. 
However, over the next couple of years, we'll be working to further 
develop this aspect of the Strategy, to develop and use information 
from assessments and other tools to guide our thinking, and to get 
input from our stakeholders. For example, once we've completed the 
initial assessment in the spring of 2000 (as described in section IV), 
we'll know better our status with regard to risk reduction goals of the 
Strategy. This will inform us about additional Federal activities 
needed to meet those goals, and what additional State, local and Tribal 
activities are needed to complement these activities. As described in 
section IV, periodic assessments will continue to inform us about 
needed programs over time. In the interim, while we're waiting for 
completion of the initial assessment, we plan to meet with our State, 
local and Tribal partners. We'll be reviewing the goals and the various 
components of the Strategy and how they interrelate. In particular, 
we'll focus on the assessment tools and their role in defining Federal, 
State and local activities, and we'll exchange information to help 
better refine the tools.

IV. Assessment Activities

    This discussion of our assessment activities first focuses on how 
we generally intend to assess progress in meeting the goals of the 
Strategy. We then discuss our methods and tools for estimating health 
risks and describe more specifically how we intend to apply these risk 
assessment methods and tools in assessing progress and in supporting 
implementation of the Strategy. However, it is important to remember 
that the NATA assessments are designed to address all of the goals and 
activities of our overall air toxics program.
    Historically, Agency risk assessment and decision-making have 
focused on the likelihood of health effects associated with exposure to 
individual environmental contaminants. In recent years, as we move from 
a focus on emissions reductions toward a focus on estimated risk 
reduction, our risk assessment emphasis has shifted increasingly to a 
greater consideration of multiple endpoints, pathways and routes of 
exposure and holistic reduction of risk. This more complex assessment 
is often called ``cumulative risk assessment,'' defined according to 
who or what is at risk of adverse effects--from identifiable sources 
and stressors--through several routes of exposure over varied time 
frames. While various integrated approaches are now being used within 
the Agency, we realize that there are significant gaps in methods, 
models and data that limit our ability to assess cancer and non-cancer 
risks associated with cumulative exposure to mixtures of pollutants 
having different endpoints. We've identified both short-term and long-
term research needs to fill these gaps, highlighted in section V.D. of 
this notice. Progress toward more refined assessments of cumulative 
risks will depend upon the pace and evolution of our policy and 
guidance on cumulative risk and the underlying research.

A. How Will We Assess Progress Toward Goals?

    Assessing progress in reducing cumulative risk from HAPs will 
require us to move away from a focus on assessing reductions in tons 
per year emitted, toward a focus on estimating reductions in cancer and 
non-cancer risks associated with lower emissions.
    ``Cancer'' describes a group of related diseases that affect a 
variety of organs and tissues. Cancer results from a combination of 
genetic damage and non-genetic factors that favor the growth of damaged 
cells. At current cancer incidence rates, approximately one third

[[Page 38730]]

of U.S. residents may be expected eventually to contract some form of 
cancer. Cancer is associated with a wide range of factors, of which 
exposure to HAPs is only one. Other causes of cancer, including genetic 
susceptibility, diet, smoking, background radiation, and lifestyle, are 
thought to be the dominant factors determining total cancer incidence. 
Given these complexities, the rate of cancers associated with HAPs 
alone cannot be observed directly. Attributing cancer to specific 
factors is also complicated by the fact that many cancers do not appear 
for years, or decades, after exposure and, therefore, may have been 
caused by exposures long past and in different locations. As a result, 
we'll need to rely on modeled estimates of cancer risk rather than on 
direct measurements for assessing the Strategy's progress toward the 
goal of 75-percent reduction in cancer incidence associated with HAPs.
    Adverse health effects other than cancer (``non-cancer risks'') 
include a wide range of health endpoints in all organ systems (for 
example, cardiovascular, immune, liver, kidney).\42\ As with cancer, 
other factors such as diet, lifestyle, and other exposures (for 
example, smoking) may exert a dominant influence over incidence of 
adverse non-cancer health effects. Therefore, as with carcinogens, we 
expect to rely primarily on risk estimates to assess progress, rather 
than on direct measurements of changes in the incidence of adverse non-
cancer health impacts due to reductions in emissions.
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    \42\ Some HAPs that cause cancer may also cause adverse non-
cancer health effects at environmentally relevant doses. Thus, when 
we discuss ``non-carcinogens,'' we mean substances that may 
potentially cause non-cancer effects in humans. Some of the same 
substances may also be evaluated as carcinogens.
---------------------------------------------------------------------------

    The Act sets a clear numerical goal for reduction in cancer 
incidence, but specifies only a ``substantial'' reduction in public 
health risks for effects other than cancer. We see a need to define and 
clarify this goal more fully as we work to implement this Strategy, but 
we haven't yet developed a specific numerical goal for risk reduction 
for various non-cancer effects. One major purpose of our non-cancer 
risk assessments will be to provide a sound technical basis for 
developing and defining non-cancer goals that are quantifiable, 
attainable, and consistent with the Act.
    Since cancer and non-cancer health impacts can't be directly 
isolated and measured, we and others have spent more than two decades 
developing an extensive set of risk assessment methods, tools and data 
that serve the purpose of estimating health risks for many of our 
programs. Our risk assessment science has been extensively peer-
reviewed, is widely used and understood by the scientific community, 
and continues to expand and evolve as scientific knowledge advances. We 
intend to use the most current and appropriate risk estimation methods 
in tracking progress under the Strategy.
    Our risk assessments, reflecting the risk paradigm set forth by the 
National Academy of Sciences in 1983,\43\ are based in general on a 
combination of two types of analyses. The first type of analysis 
examines what adverse effects a substance causes (the ``hazard 
identification''), and the specific exposures at which these effects 
occur (the ``dose-response assessment''), and is usually based on human 
or animal studies of high quality published in peer-reviewed scientific 
journals. This type of analysis allows us to evaluate a chemical's 
potential to cause cancer and other adverse health effects.
---------------------------------------------------------------------------

    \43\ National Research Council (NRC). 1983. Risk assessment in 
the federal government: Managing the process. National Academy 
Press, Washington, D.C.
---------------------------------------------------------------------------

    The second type of analysis estimates the levels of exposure that 
people receive within the environment. We develop this ``exposure 
assessment'' in stepwise fashion for air pollutants, with the first 
step being the compilation of emissions data. Second, these data are 
input to a dispersion model, which estimates ambient air 
concentrations. These modeled ambient concentrations may be compared to 
monitoring data in order to test and validate the models. Third, we 
estimate exposures to ambient concentrations by applying models of 
human behavior patterns, and incorporate measured personal exposure 
information when available.
    These two types of analyses--the exposure that causes harm and the 
exposure people actually receive--are combined in a ``risk 
characterization'' that describes the potential for real-world 
exposures to cause harm, and the uncertainties surrounding the 
characterization.

B. What Methods, Tools, and Data Will We Use To Estimate risk?

1. Evaluating a Chemical's Potential To Cause Cancer
    Our dose-response assessments for carcinogens are based on 
mathematical models and assumptions that support extrapolation from 
high to low doses and from non-human test species to humans. As a 
matter of science policy, many of these assumptions are protective, to 
avoid underestimating cancer risks where data are incomplete. The most 
important of these assumptions for most carcinogenic chemicals is that 
risk is proportional to dose, with no threshold dose below which there 
is no risk. Our dose-response assessments for inhalation of carcinogens 
are expressed as a ``unit risk,'' that is, risk per microgram per cubic 
meter of daily exposure during a lifetime. The unit risk is defined as 
a conservative estimate of an individual's excess probability of 
contracting cancer at the end of 70 years exposure to a continuous 
level of one microgram per cubic meter. Risks from exposures to 
concentrations other than one microgram per cubic meter are modeled as 
proportional, with half the concentration producing half the estimated 
risk, and so on.
    Each word in the above definition of unit risk carries significant 
meaning. First, the unit risk is a conservative rather than a ``best'' 
estimate. This means that the actual unit risk is unknown, and is very 
likely to be lower than estimated and very unlikely to be higher. 
Second, as already described, risks are estimated rather than measured. 
Third, the unit risk applies to an individual, although cancer 
incidence in a population can be estimated across a group by 
aggregating the risk of each person. Fourth, unit risk estimates focus 
only on the route of exposure being analyzed. Fifth, unit risks are 
expressed in terms of probability. For example, we may determine the 
unit risk of a particular HAP to be one in ten thousand per microgram 
per cubic meter. This means that, of ten thousand people who 
continuously inhale an average of one microgram per cubic meter of this 
particular HAP for 70 years, no more than one would be expected to 
contract cancer from the exposure. Sixth, risks are generally expressed 
in terms of contracting cancer, not dying from it. Finally, exposures 
are averaged over a 70-year lifetime, to account for long-term 
exposures to low levels of carcinogens.
    We intend to use unit risk estimates as the dose-response component 
in estimating plausible reductions in cancer incidence achieved by this 
Strategy.
2. Evaluating a Chemical's Potential To Cause Adverse Effects Other 
Than Cancer
    Adverse health effects other than cancer (``non-cancer risks'') 
cover a wide range of health endpoints in all organ systems (for 
example, cardiovascular, immune, liver, kidney).

[[Page 38731]]

For this reason, we've developed our non-cancer dose-response 
assessment methods to address several additional sources of complexity 
beyond those found in cancer assessments. First, organisms possess 
varying abilities to eliminate, detoxify, and sequester many toxic 
substances, and to repair some amount of damage that those toxic 
substances may cause to tissues and organs. For this reason, most 
chemicals don't cause observable adverse non-cancer health effects 
until some threshold dose has been exceeded. Second, the appearance of 
a toxic response when the threshold dose is exceeded is seldom 
proportional to dose. The shape of ``dose-response curves'' (for 
example, a graph of the number of individuals affected at varying dose 
levels) varies substantially among chemicals, so there is no single 
model that can be applied to all non-carcinogens. Third, available 
information for most HAPs comes from animal studies, and significant 
uncertainty is associated with extrapolating these results to humans to 
support predictions of human dose-response curves.
    For these reasons, non-cancer dose-response assessments for 
inhalation are usually expressed in terms of a ``reference 
concentration,'' defined as an estimate (with uncertainty spanning 
perhaps an order of magnitude) of a continuous inhalation exposure to 
the human population (including sensitive subgroups) that is likely to 
be without an appreciable risk of deleterious non-cancer effects during 
a lifetime. We intend to use reference concentrations as the dose-
response component for estimating reductions in non-cancer risk 
achieved by this Strategy.\44\
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    \44\ The uncertainty surrounding reference concentrations (RfCs) 
varies substantially among HAPs, depending on the strength of the 
supporting data. As a result, RfCs vary in their level of 
protectiveness, with RfCs supported by strong toxicological data 
tending to be less protective. We recognize this important 
limitation to the use of RfCs, and may use more advanced dose-
response models for specific HAPs where they can be applied.
---------------------------------------------------------------------------

3. Assessing Exposures and Characterizing Risks
    In general, the choice of appropriate risk characterization 
approaches will be influenced by both the availability of data to 
support exposure assessment, and the level of detail and resolution 
needed to support the purpose of the assessment. Possible approaches 
span a wide range, from simple weighting adjustments of emissions data 
or ambient concentrations, to detailed multipathway risk assessments. 
We've identified four basic approaches that we plan to use for various 
assessments to evaluate the progress of the Strategy in reducing 
estimated risk. Each of these approaches uses the same dose-response 
information described above, but relies on different types of data to 
represent exposures. The four basic approaches we intend to use are: 
(1) Emissions or ambient concentration weighting;(2) comparisons 
between ambient concentrations and risk-based concentrations (RBCs) 
\45\; (3) comparisons between estimated exposures and RBCs, that may 
yield quantitative estimates of risk; and (4) quantitative estimates of 
carcinogenic risk for individuals and populations.
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    \45\ Risk-based concentrations for cancer are ambient 
concentrations associated with specific levels of cancer risk, 
assuming 70 years of continuous exposure. RBCs for non-cancer 
effects are ambient concentrations that pose no appreciable risk to 
humans, assuming continuous exposure. The use of RBCs does not imply 
a judgement that the concentrations are either acceptable or 
unacceptable, only that they have been derived in the same way for 
all HAPs.
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    Approaches (1) and (2) are considered hazard-based approaches, in 
that they lack the dispersion and/or human exposure modeling steps of 
an exposure assessment and therefore cannot provide quantitative 
estimates of risk. However, they can provide valuable information, 
subject to substantial uncertainty, that may be useful in evaluating 
progress toward risk reduction goals. In contrast, approaches (3) and 
(4) are considered risk-based approaches, in that they do incorporate 
exposure assessments and thereby can provide quantitative risk 
estimates.
    (1) Weighted emissions or ambient concentrations. Weighting of 
emissions or ambient concentrations is the least resource-intensive 
approach of the four in terms of data needs and computational 
requirements.\46\ This hazard-based approach combines HAP emissions or 
monitored HAP concentrations (acting as surrogates for exposure) with 
weighting factors (developed from unit risks and reference 
concentrations) that account for differences in relative toxicity among 
HAPs. Other weighting factors could also potentially be developed to 
account for differences in dispersion characteristics or variations in 
population density or behavior.
---------------------------------------------------------------------------

    \46\ Peer-reviewed examples of this approach include the EPA/
OPPT Risk-Screening Environmental Indicators, the EPA/OSW Waste 
Prioritization Management Tool, and the EPA/OAQPS ranking analysis 
for urban HAPs. See the public docket for a detailed list of risk 
assessment references.
---------------------------------------------------------------------------

    The toxicity adjustment is intended to account for differences in 
toxic potency among substances, placing all emissions data on the same 
scale of hazard potential. For example, acrylamide is approximately 160 
times more potent a carcinogen than benzene, such that weighting by 
toxicity would consider one ton of acrylamide emissions equivalent to 
160 tons of benzene. In a cumulative analysis, emissions or 
concentrations of each HAP would be weighted by its relative toxicity 
to allow for direct comparison and aggregation across HAPs (with 
carcinogenic and non-carcinogenic estimates aggregated separately). 
This type of analysis permits comparisons of relative hazard between 
pollutants with large mass emissions and low toxicity (for example, 
many non-chlorinated volatile compounds) against pollutants with small 
mass emissions but high toxicity (for example, dioxin).
    As discussed above, the weighted emissions-or concentration-based 
approach lacks the last two steps of an exposure assessment, and 
therefore doesn't provide a quantitative estimate of risk. Also, 
because of the absence of these important exposure assessment steps, it 
isn't possible to say how closely changes in weighted emissions or 
concentrations will be related to changes in health risk. Nevertheless, 
emissions and ambient concentrations clearly have a strong influence 
over exposure and risk, and we anticipate that the toxicity-weighting 
approach will provide useful information to estimate progress where 
appropriate data for more refined assessment approaches aren't 
available.
    (2) Ratios of ambient concentrations to RBCs. A second type of 
hazard-based approach is the comparison of ambient HAP concentrations 
with RBCs.\47\ Ambient concentrations may be measured (as discussed in 
section V.A.) or modeled (section V.C.). Appropriate modeling 
approaches for estimating ambient concentrations at different spatial 
scales using emissions data include national-scale and urban-to 
neighborhood-scale air quality models, as well as multi-media models 
for urban-to neighborhood-scale analyses.
---------------------------------------------------------------------------

    \47\ Peer-reviewed examples of the use of this approach include 
the concentration-toxicity screen used by EPA's Superfund program to 
select contaminants and exposures for detailed risk assessment, and 
EPA's Cumulative Exposure Project, which compared modeled ambient 
air concentration estimates with RBCs (termed Ahealth benchmarks'' 
by the authors) for 148 HAPs nationwide. See the public docket for a 
detailed list of risk assessment references.
---------------------------------------------------------------------------

    The RBCs used for comparison are derived from unit risks or 
reference concentrations. Specifically, cancer RBCs can be defined in 
terms of a fixed risk level (for example, HAP concentrations 
conservatively estimated to result in a one-in-ten-thousand or a

[[Page 38732]]

one-in-one-million upper-bound risk of contracting cancer from a 
lifetime exposure at the RBC). Non-cancer RBCs can be defined in terms 
of estimates of continuous exposure levels at which even sensitive 
subgroups are likely to be without any appreciable risk of adverse 
effects during a lifetime.
    Because it is more complex than emissions-weighting, this type of 
analysis brings two significant advantages. First, it supports a more 
complete treatment of ambient HAP concentrations that are already below 
non-cancer RBCs, for which further reductions may not carry significant 
health benefits. Second, the use of dispersion models to predict 
ambient concentrations can potentially account for variations in 
factors such as location of exposed populations relative to sources of 
HAPs, differences in meteorological conditions, and differences in fate 
and transport characteristics among HAPs.
    Nevertheless, this approach still lacks the third, human behavior-
related, step in an exposure assessment. Therefore, it doesn't provide 
a quantitative estimate of risk, and its use in estimating progress is 
subject to greater uncertainty than approaches (3) and (4), below. 
Changes in health risk may not precisely track changes in 
concentration/RBC ratios. However, because ambient concentrations are 
important determiners of exposure and risk, we anticipate that the 
concentration/RBC approach will provide useful information to estimate 
progress where exposure assessment is not possible.
    (3) Ratios of exposures to RBCs. A third type of approach begins 
with measured or modeled ambient HAP concentrations, and adds further 
refinement by overlaying estimates or measurements of population 
exposures. Thus, this risk-based approach is qualitatively different 
from the first two hazard-based approaches because it incorporates all 
three steps of an exposure assessment.
    While human exposures are directly affected by ambient 
concentrations, they're also influenced by behavioral factors such as 
time spent outdoors, periodic movements (such as commuting) within an 
urban area, and activity levels. Exposures may be estimated with 
exposure models, as discussed in section V.C., that simulate the 
behavioral factors that determine exposure. Human exposure may also be 
directly measured by personal monitoring, in which subjects wear small 
air samplers and record their daily activities.
    These estimated or measured exposures are then compared to RBCs 
\48\ (as described above for approach (2)). Analogous to the 
comparisons in approach (2), hazard potential would typically be 
presented in terms of ratios of the exposure concentrations divided by 
RBCs. The additional complexity of estimating exposure provides three 
significant advantages over considering ambient concentrations alone. 
First, it provides a more realistic comparison with RBCs, which are 
based on unit risks and reference concentrations usually derived from 
doses actually received by test organisms. Second, exposure estimates 
can take into account behavioral differences between populations in 
different cities, or between different demographic groups. Third, 
exposure estimates support combining effects of multiple HAPs, 
considering non-additivity and similarities or differences in toxic 
mechanisms. Comparison of exposures with reference concentrations for 
non-cancer effects (acting as RBCs) is currently the most advanced 
approach available for assessing non-carcinogenic HAPs, although this 
may change in the future for some substances.
---------------------------------------------------------------------------

    \48\ Peer-reviewed analyses of this type of analysis include 
many single-substance risk assessments. Several examples concern the 
fuel additives methylcyclopentadienyl manganese tricarbonyl (MMT) 
and methyl tertiary butyl ether (MTBE). See the public docket for a 
detailed list of risk assessment references.
---------------------------------------------------------------------------

    (4) Risk estimation. A fourth type of approach that can be used to 
estimate cancer incidence is comprehensive risk estimation, focusing on 
the most exposed individual or on entire populations or subgroups.\49\ 
We'll derive risk estimates by combining exposure estimates with dose-
response assessment results in terms of unit cancer risk estimates. 
Risk estimates will also consider non-standard dose-response models and 
complex interactions among different HAPs, if information is available. 
Such risk estimates represent the most refined analysis of the four 
approaches considered. Comprehensive assessments may contain modeling 
to account for environmental fate and transport of released pollutants, 
estimation of exposures to different subpopulations, detailed dose-
response assessments for each HAP, and information on complex, non-
additive interactions among HAPs. Results are expressed in terms of 
probabilities of developing cancer during a lifetime. Cancer risks are 
usually aggregated across HAPs by addition, but non-additive 
interactions are included if data permit.
---------------------------------------------------------------------------

    \49\ Examples of such multi-chemical, multipathway risk 
assessments include many performed by EPA's Superfund program under 
the Risk Assessment Guidelines for Superfund. See the public docket 
for a detailed list of risk assessment references.
---------------------------------------------------------------------------

    In its most complete form, risk estimation produces results in 
probabilistic form (that is, with calculations considering a range of 
cancer risks and the likelihood of each), expressed in terms of a 
frequency distribution rather than as a single deterministic estimate. 
Of currently available approaches, risk estimation, presented 
probabilistically, provides the most complete, best-supported, and most 
accurate presentation of both risk and the variability and uncertainty 
surrounding it. However, this risk-based approach is much more 
resource- and calculation-intensive than are simpler approaches.
4. Summary
    We anticipate tracking progress in reducing estimated cumulative 
risks from air toxics in urban areas by relying on estimates of health 
risk rather than by directly observing reductions in adverse health 
impacts in human populations. We consider these health risk estimates 
to be reasonable and appropriate indicators of progress toward meeting 
the goals of the Strategy. Their use is made necessary by the long 
latency period for cancer, the high background rate of human cancer 
from all sources, and complexities involved in attributing various non-
cancer health effects to specific environmental causes. Our assessments 
will use a variety of approaches, including some that do not include 
all exposure assessment steps. In some cases the information may be too 
uncertain to support conclusions. We intend to evaluate these 
approaches against each other, in terms of their ability to estimate 
risk and their resource and data requirements, when supporting data 
become available in early 2000. These results will assist us in 
determining the scope, refinement, and precision of future assessments 
developed to reflect different purposes under the Strategy.

C. What Is Our Overall Risk Assessment Approach for the Strategy?

    In section I, we discussed the key role that assessing air quality, 
exposure, and estimated risks will play in assessing progress toward 
meeting the goals of this Strategy. In addition, these assessment 
activities will, over time, also serve the following broader purposes:
     Improve the definition of the goal for ``substantial'' 
reduction in non-cancer risk.

[[Page 38733]]

     Support development of Federal area (as described earlier) 
and mobile (as appropriate under section 202(l)) source standards.
     Support decisions on how to conduct future risk 
assessments.
     Evaluate the effectiveness of each of the four approaches 
to characterizing risk reductions, described above.
     Provide guidance for State, local and Tribal agency 
efforts in conducting local assessments and developing risk reduction 
programs at the state and local levels.
    Our assessment approach will be basically iterative in nature, so 
as to take advantage of emerging science, new data, and improved tools 
that become available at the time future assessments are performed. 
Consistent with this approach, beginning in early 2000, we'll conduct 
an initial set of assessments that will be based on final, updated 
emissions data, as discussed in section IV.D. Subsequent assessments 
will reflect the best available data, methods, and tools available at 
the time the assessments are performed.
    Our national database of air toxics emissions from major, area, and 
mobile sources (including diesel exhaust), the NTI, will be a 
fundamental component of our risk assessments. We are now completing a 
baseline NTI representing the 1990-1993 period, and obtaining State 
review of a draft 1996 NTI suitable for use as input data for 
dispersion and exposure models (scheduled for completion in the fall of 
1999). We plan to update the NTI every three years, and to conduct 
subsequent risk assessments to coincide with these revisions. Monitored 
air toxics concentrations will also be an important component of our 
assessment activities, in part to help us evaluate and refine our air 
quality models. We are now working with the States to design and 
implement a national air toxics monitoring network that will provide 
important information for future assessment activities. Our plans for 
the ambient monitoring network are described in more detail in section 
V.A.
1. How We Will Design Our Assessments
    We'll tailor each assessment to the purpose(s) it is to serve 
(e.g., measuring progress against the 75-percent estimated cancer 
incidence reduction goal). Accordingly, assessments will vary in scope, 
level of refinement, and, thus, data and resource requirements. The 
scope of each assessment will generally be defined by the following 
characteristics:
     The number of HAPs to be evaluated (all 188 or some 
subset);
     Types of source included (area, major, mobile);
     Spatial resolution (for example, aggregation of results on 
the national, state, urban, or neighborhood scale); and
     Pathways/media to be evaluated (inhalation/air only or 
multipathway/multimedia).
    Further, for each assessment, we need to specify an appropriate 
approach to use in estimating progress toward our risk reduction goals, 
since, as discussed above, it will not be possible to directly measure 
reduction in cancer incidence or non-cancer risks attributable to 
hazardous air pollutant emissions. Alternative approaches, discussed in 
section IV.B., range from rough approximations to more precise risk 
estimates, with data and resource requirements increasing for more 
precise assessments that require greater refinement.
2. How Our Assessments Will Address Disproportionate Risks
    Disparities in risks from air toxics in the urban environment may 
exist between different cities, between neighborhoods or demographic 
groups within a city, or within a similarly-exposed population that 
includes sensitive groups. In our assessments, we intend to pay 
particular attention to areas, populations, and sensitive groups with 
substantially higher-than-average risks.
    While differences in risk between different urban areas may be 
discernible from national screening-level modeling, more refined 
modeling will generally be needed to evaluate localized disparities 
within any one urban area. This is because highly localized disparities 
may be obscured by the simplifying assumptions that are necessarily 
inherent in national screening-level assessments. For this reason, the 
ability of EPA or State and local authorities to assess localized risk 
disparities will depend on the availability of detailed data on 
emissions and population distribution, local-scale models, and 
sufficient resources.

D. How Will We Design Future Assessments?

    We'll conduct a series of assessments starting in early 2000 and 
periodically thereafter at appropriate times during the implementation 
of the Strategy. The assessments will include both national-scale and 
urban-scale analyses. All assessments will incorporate the most current 
data, information, and assessment tools available at the time they are 
performed. As the Strategy progresses, we may eventually use risk 
assessment tools that are now only in early development, or perhaps 
have not yet been envisioned. For this reason, we can't describe in 
detail assessments that will be conducted several years from now.
1. Initial Assessments--National
    We'll conduct an initial national assessment in early 2000. This 
assessment will define an appropriate hazard-or risk-based approach 
consistent with the limited available information on HAP emissions and 
ambient concentrations. The principal limitation of the baseline 
emissions information is that, although the baseline NTI will be a 
comprehensive county-level inventory, it will lack the source-specific 
information necessary to support air quality modeling.\50\ Thus, any 
assessment of progress relative to the base year will be limited to 
using either a weighted emissions or a weighted ambient concentration 
analysis, since the other approaches include an air quality modeling 
step. Future assessments, however, will not be limited in this way 
because emission inventory data, beginning in 1996, will include 
information needed for modeling.
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    \50\ We note here, as discussed in sections I.B. and II.A., that 
as part of the Agency's Cumulative Exposure Project, the ASPEN model 
to estimate HAP ambient concentrations nationwide was developed and 
tested using a 1990 emissions inventory that was based on the 
limited HAP information available in the mid-1990s prior to the 
substantial improvements that are now reflected in the baseline NTI. 
While that first national-scale modeling exercise provided 
screening-level information that we've used in conjunction with 
other information in selecting the urban HAP list, we believe that 
the uncertainties in the CEP's 1990 emission inventory are too large 
to support a meaningful comparison with modeled concentrations for 
future years that will result from the application of the ASPEN 
model using updated emissions inventories. These updated 
inventories, starting with the 1996 NTI, are specifically designed 
to include sufficient source-specific information to support air 
quality modeling.
---------------------------------------------------------------------------

    The initial assessment will serve several purposes. First, we'll 
develop an estimate of progress that has already been made toward the 
goals of the Air Toxics Program and the Strategy. Consistent with 
section 112(k) of the Act as amended in 1990, which focuses on 
reductions ``below those currently experienced,'' we've established 
1990 as the base year for assessing progress. To estimate progress 
since the base year, we'll compare the base year emissions inventory to 
the inventory for 1996, due to be completed in fall of 1999, using a 
weighted emissions analysis. This assessment will be limited to the 
weighted-emissions approach because the base year inventory (although a 
comprehensive county-level inventory) will lack the source-specific 
information

[[Page 38734]]

necessary to support air quality modeling. Subsequent assessments, 
however, will not be limited in this way because emission inventory 
data, beginning in 1996, will include information needed for 
modeling.\51\
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    \51\ Peer-reviewed examples of this approach include the EPA/
OPPT Risk-Screening Environmental Indicators, the EPA/OSW Waste 
Prioritization Management Tool, and the EPA/OAQPS ranking analysis 
for urban HAPs. See the public docket for a detailed list of risk 
assessment references.
---------------------------------------------------------------------------

    Second, the initial national assessment will provide basic 
information to assist us in prioritizing HAPs and area, mobile, and 
major source categories for regulations to be developed consistent with 
section 112(k), section 202(l) and other authorities (e.g., residual 
risk), respectively, based on their relative importance as contributors 
of risk. Third, the assessment will provide the clearest and most 
current picture of inter-urban and demographic disparities in risk, and 
will provide insight on more refined analyses that may be appropriate 
to identify types of sources associated with particularly high risk 
levels. Fourth, we intend to use information from the initial 
assessment to develop a more complete and quantitative goal for a 
``substantial'' reduction in non-cancer risk. Finally, we'll use the 
initial assessment to compare different hazard- and risk-based 
approaches. In particular, we intend to correlate results of assessment 
approaches (1) and (2) (which lack exposure assessments) with exposure 
assessment-based approaches, to determine their relative accuracy and 
to quantify uncertainties. These comparisons, in combination with data 
and resource availability, will help us to scope the details of future 
assessments and finalize our estimates of progress from 1990 to 1996.
    We'll use all four types of approaches (emissions weighting, 
comparisons between ambient concentrations and exposure estimates and 
RBCs, and modeled estimates of risk) in the initial national 
assessments, to the extent possible. As discussed in section V.C., we 
plan to use the ASPEN model to estimate national air quality 
concentrations in conjunction with the use of the Hazardous Air 
Pollutant Exposure Model (HAPEM) to estimate national exposures. We'll 
conduct screening level analyses before progressing to more refined 
analyses, to ensure that we're allocating appropriate amounts of 
resources to each assessment, given our information needs. The 
assessment will focus on inhalation exposures, with the expectation of 
including multipathway exposures, as appropriate, in subsequent 
assessments. The initial assessment will include all urban areas in the 
United States, and we anticipate presenting results with county- and/or 
urban-scale resolution. The assessment will address as many HAPs as the 
data support, but will include at least the 33 urban HAPs and diesel 
PM.
2. Initial Assessments--Urban
    We plan to conduct urban-scale assessments for a number of selected 
cities to serve as case studies that may be particularly useful as 
guidance for State, local and Tribal program assessments. We'll also 
provide technical support and risk assessment tools for authorities 
that wish to conduct their own local assessments to analyze area-
specific progress and intra-urban disparities. The experience we gain 
through these analyses will also help us refine future assessments.
    We'll develop these initial urban assessments using the specific 
approaches that are appropriate for the quality of data available. Each 
assessment will describe a single urban area, and we anticipate 
presenting the results with high spatial resolution (for example, a 1-
kilometer grid). The scope of each assessment will address a subset of 
HAPs that we identify as being priority HAPs for the particular urban 
area being assessed. We plan to consider both inhalation and 
multipathway exposures as appropriate and as available data permit.
3. Periodic Assessments
    In the years following the initial national assessment, we'll 
conduct new analyses at appropriate intervals as new data become 
available. These periodic assessments will serve two principal 
purposes. First, they'll measure progress toward the goals of the 
Strategy, considering all actions taken that reduce HAP emissions 
(including Federal, State, local and Tribal actions, as well as 
voluntary initiatives by local communities and industry) for any 
purpose. Second, they'll assist us in prioritizing which future 
regulatory actions would be most effective in making needed further 
progress. We'll develop the periodic assessments using the specific 
approaches that have proved most efficient (that is, the least 
resource-intensive approach that accomplishes the purpose of the 
assessment). Assessments will include all urban areas in the United 
States, with results presented on county- and urban-scale level 
resolution. Assessments will address the full list of 188 HAPs, to the 
extent to which emissions, monitoring, and health data are available. 
If appropriate tools become available, periodic assessments for 
bioaccumulative HAPs will include multipathway exposures.
    By measuring ongoing progress, periodic assessments will also 
inform us when we have met our goals, and will help us to measure the 
degree to which we have reduced disparities in risk. The approaches 
used for such goal-specific comparisons will be determined by the 
results of earlier assessments, and developed to fit the Strategy's 
purpose.

V. Knowledge and Tools

    This section describes the activities we'll undertake to improve 
our base of knowledge (e.g., concerning health effects and exposure 
characteristics) and tools (e.g., emissions inventories, monitoring 
networks, and computer models), along with our plans for their 
improvement and related research.

A. How Will We Review and Expand Ambient Monitoring Networks?

1. Need for Ambient Data
    As described in section IV, our iterative approach to risk 
characterization looks at emissions as a rough surrogate for risks in 
the near-term, while providing for a plan to periodically conduct more 
refined analyses as risk tools and data are developed. In order to base 
the air toxics program on risk assessments backed by sound science, 
we'll need emissions and monitoring data to conduct good assessments. 
Emissions data are one way we can attribute HAP exposures to specific 
sources. On the other hand, ambient monitoring data allow us to 
continually evaluate and improve our models and inventories, to deal 
credibly with the difficult issue of background HAP concentrations, and 
to measure progress more directly. Furthermore, each type of data 
(source emissions data and ambient monitoring data) can be used to 
improve our understanding of the other. For example, ambient data can 
warn us when our inventory or models are seriously flawed, and modeled 
exposures can be used in siting monitors and directing analyses for 
both short- and long-term measurements.
2. Ambient Monitoring Network Program Design
    Currently, we have limited data on ambient concentrations of air 
toxics, because existing networks are limited, were developed for other 
purposes, or weren't specifically designed to develop the data needed 
to meet our current air toxic program goals. In fact, many commenters 
raised concerns that the current monitoring network was

[[Page 38735]]

inadequate and that the draft Strategy didn't adequately address this 
concern. Another problem is that ambient data can be both difficult and 
expensive to obtain. Our long-term plan is to build an air toxics 
monitoring network consistent with the goals of the air toxics program 
and the Strategy.
    Since it's not possible to monitor everywhere, we must develop a 
monitoring network that is representative of air toxics problems on a 
national scale, but that still provides a means of obtaining data on a 
more localized basis as appropriate and necessary. The appropriateness 
of a candidate monitoring site with respect to the projected uses of 
its data is a key consideration in identifying sites for the national 
network. For example, in selecting monitor locations we must evaluate 
how well the location allows us to directly evaluate public exposure 
and environmental impacts in the vicinity of the monitors. We'll also 
need to site monitors to allow us to obtain data that can help us 
establish an ambient baseline for toxics risk characterization, track 
trends in ambient levels to assess progress in meeting our emission and 
risk reduction goals, and assess the effectiveness of specific emission 
reduction activities.
    We'll design the monitoring network to address all of the needs of 
the air toxics program and the Strategy, which should satisfy the 
following objectives:
     Measure pollutants of concern to the overall air toxics 
program and the Strategy.
     Use scientifically sound monitoring protocols to ensure 
nationally consistent data of high quality.
     Collect a sufficient amount of data to estimate annual 
average concentrations at each monitoring site.
     Complement existing national and State/local monitoring 
programs.
     Reflect Acommunity-oriented'' (i.e., neighborhood-scale) 
population exposure, including inhalation and non-inhalation exposure.
     Represent geographic variability in average ambient 
concentrations.
3. Network Implementation Schedule
    For the first 2 years of monitoring, we'll maximize our use of 
existing State/local air toxics monitoring sites, Photochemical 
Assessment Monitoring Stations (PAMS) sites, or planned particulate 
matter chemical speciation sites. These sites should provide coverage 
of both the largest metropolitan areas and neighborhood-scale sites, 
which fits with our focus on population-oriented urban sites. If 
existing platforms aren't suitable for characterization of population 
exposure to air toxics, we'll strive to establish new community-
oriented monitoring stations or upgrade existing ones to include urban 
HAP analyses. We'll also work to establish appropriate quality 
assurance, data management, data analysis, and data submission 
procedures, and will use established monitoring protocols in the next 
few years.
    After 2000, we expect the air toxics monitoring network to continue 
to grow to cover more urban areas and to include monitors in rural 
areas to permit estimates of background concentrations. We also expect 
to place other fixed-site monitors in areas that may be subject to 
localized high concentrations of air toxics. In some cases, temporary 
or mobile monitors may be used to evaluate these areas. The long term 
goal for a national network includes monitoring of sensitive ecosystems 
and other environmental concerns. To this end, the national network 
should incorporate the separately funded deposition monitoring 
activities associated with the Great Waters Program. Our tentative 
projection of the national network is 200 sites, but this will be 
revised as additional information becomes available and as the network 
itself expands.

B. How Will We Update and Maintain the Emission Inventory?

    We plan to update the NTI every 3 years using the same principles 
that we used when developing the 1996 NTI. The next version will be 
known as the 1999 NTI. The 1996 and subsequent NTIs will be compiled 
from State and local air toxics inventories. The State and local 
emission inventory data are supplemented with data gathered to support 
the development of MACT standards and Toxic Release Inventory (TRI) as 
well as calculated emission estimates for the majority of area and 
mobile sources. Unlike the baseline inventory developed for the 
Strategy, the 1996 and subsequent NTIs will contain location- and 
facility-specific data making the inventory suitable for input to 
dispersion and exposure modeling. These additional data are used to 
determine the exact types and location of facilities in urban and rural 
areas. We also expect that the quality of information available to use 
in developing future inventories will improve as data quality does and 
as we learn more about the locations and sources we are studying.
    As discussed in the rest of section V, we plan to obtain improved 
monitoring data that will influence our inventory efforts, as well as 
to undertake research projects to address our data needs. One tool 
we're in the process of developing is the consolidated emissions 
reporting rule, whose purpose is to simplify reporting, offer options 
for data exchange, and unify reporting dates for various categories of 
inventories.

C. What Air Quality and Exposure Models Will We Use To Implement the 
Strategy?

    A variety of mathematical models are often employed to assist in 
risk assessment activities. While not designed specifically to address 
urban areas, several models are currently available or under 
development to help describe the fate and transport of toxic air 
pollutant emissions. Although there is much associated uncertainty, the 
output of such models is then used as input to models that estimate 
human exposure and risk. This section discusses the model development 
activities and models that will be used in the air toxic assessments 
discussed in section IV.
    We'll rely on a variety of fate and transport modeling tools that 
vary in their complexity and the scale of the geographic area that 
they're capable of handling. For example, we plan to use the Assessment 
System for Population Exposure Nationwide (ASPEN) model to conduct 
national screening modeling for ambient (i.e., outdoor) air toxic 
concentrations. This model estimates annual average ambient air toxic 
concentrations by modeling the dispersion of a nationwide inventory of 
HAP emissions from major, area, and mobile sources. It can also address 
simple chemical transformations of air toxics in the atmosphere. 
Current developmental efforts are underway to add increased model 
functionality to allow for testing of various ``what-if'' emission 
reduction scenarios using the ASPEN model. We'll use the Industrial 
Source Complex Short-Term (ISCST3) model to estimate both short-term 
(one-hour) and long-term (annual) average concentrations at locations 
from the urban to neighborhood scales. The ISCST3 model can predict not 
only ambient air toxic concentrations, but the amount of air toxic 
pollutants that will settle to the soil and/or into bodies of water. 
These settling rates are sometimes used to track the fate of air toxic 
pollutants where multimedia (air, water and/or soil) exposure and risk 
are of concern (e.g., with mercury). When multimedia considerations are 
of concern, we'll use the environmental fate and transport module of 
the Total Risk Integrated Methodology (TRIM) to determine urban and 
neighborhood scale impacts. Likewise, when a HAP

[[Page 38736]]

associated with complex chemical reactions in the atmosphere is being 
considered, we'll use the Community Multiscale Air Quality (CMAQ) 
Model. This model is currently being developed in the EPA's Models-3 
Framework, and it can be used to predict regional and urban wide 
concentrations values. The Models-3 Framework also employs a state-of-
the-art meteorological pre-processor for accurate and detailed 
simulation of the meteorological data for input into the CMAQ model.
    Model estimates of HAPs in the ambient air (and water and soil, 
when appropriate) will provide input necessary for modeling exposures. 
An exposure assessment takes into account the fact that most people 
don't spend the majority of their lives in an outdoor environment. An 
exposure model can track day-to-day activity patterns, simulating the 
movement of population subgroups (e.g, children under 5 years of age) 
through different ``micro-environments'' (e.g., in homes, vehicles, 
school, work, or while bathing). These activity pattern relationships 
are then used to estimate levels of exposures of population subgroups 
to the HAPs. One such model that we've developed for determining 
inhalation exposures is the Hazardous Air Pollutant Exposure Model 
(HAPEM4). This model can work in tandem with the ASPEN model to predict 
long-term nationwide-scale inhalation exposures to HAPs. Applications 
requiring exposure estimates through multipathway routes (e.g., through 
inhalation, ingestion and dermal contact) can use the TRIM module, 
TRIM.Expo, which is currently under development. We're currently 
developing several other exposure models for specific applications that 
we may also consider in our air toxic assessments.
    As is the case with any mathematical simulation, the more detailed 
and accurate the simulation required, the more complex the input data 
requirements become. The availability, type, and quality of input data 
will directly influence the choice of the model or models selected for 
specific assessment purposes. Where gaps between input data and the 
required level of detail and accuracy are identified, we're making 
efforts to supplement and improve our data sets (e.g., improvements in 
the NTI, establishment of national monitoring networks) to make use of 
the most state-of-the-art models available.

D. What are the Research Needs and What is EPA Doing to Address Them?

    The Strategy describes the process we'll use for identifying the 
various risks that may be present in an urban environment. Part of that 
process is to determine gaps in our scientific information and to 
identify the tools we'll need to assess urban risks and to implement 
the risk reduction elements of the Strategy. To address this concern, 
we plan to include a ``research needs'' chapter in our forthcoming 
``Integrated Urban Air Toxics Report to Congress'' (Urban Report), 
which will describe the activities and research that will be needed to 
assist in our assessment and management of risks in urban 
environments.\52\ The Urban Report will describe the research 
activities we'll undertake with the support of our Office of Research 
and Development, the research activities to be done by organizations 
outside of EPA and funded through our Grants program, and the research 
activities described in various other EPA reports that have relevance 
to the Strategy. We're also developing an ``Air Toxics Research 
Strategy'' (Research Strategy) which will expand on the planned urban 
``research needs'' chapter, to include information that would assist in 
assessing risks on a national or regional basis.\53\ This Research 
Strategy would reflect the needs of other elements of the air toxics 
program, such as the residual risk and Great Waters elements.
---------------------------------------------------------------------------

    \52\ We hope to release the ``Integrated Urban Air Toxics Report 
to Congress'' this summer.
    \53\ The ``Air Toxics Research Strategy'' will be finalized in 
fall 1999.
---------------------------------------------------------------------------

    In our Urban Report, we plan to present research needs using the 
risk assessment/risk management paradigm developed by the National 
Academy of Sciences as the basis for the requested research. This 
paradigm includes activities related to health and dose-response, 
emissions and exposure characterization, a risk assessment, and risk 
management. Briefly, the following identifies the research areas and 
describes some of our current activities:
    Urban HAP health effects and dose response needs.
     Additional knowledge of both cancer and non-cancer health 
effects will be accumulated. This will include determinations of 
specific toxicities (determined from animal and human studies) as well 
as the development of models to extrapolate across HAPs, species, time, 
and routes of exposure. Any such determinations should address the 
effects of HAPs or other factors which make sensitive subpopulations 
(e.g., children, the elderly, persons with existing illnesses) more 
vulnerable to exposure and effects.
     Development and updating of HAP health reference values, 
such as inhalation reference concentrations, acute reference exposure 
values, and cancer unit risk factors.
     Statistical methods for quantifying and reducing 
uncertainty in risk assessments using acute and chronic data.
    Emission characterization needs.
     Development of methods for measuring HAPs in emissions and 
for monitoring the ambient and indoor air, and the environment (e.g., 
deposition to water). The resulting measurements will be used to 
improve the spatial characterization of potential exposures and to 
establish a baseline against which modeling concentrations may be 
compared.
     Improved procedures to estimate and assess HAP emissions 
in a representative number of cities, and to extrapolate results to 
other locations.
     Improved models that include multiscale air dispersion 
models (neighborhood, urban, and regional) which consider atmospheric 
transport, fate, and their potential transformation products and which 
can simulate microenvironments when estimating inhalation exposures to 
urban HAPs.
    Exposure characterization needs.
     Improved data to better understand the potential for 
disproportionate impacts on those who are more susceptible to HAP 
exposures including minority and low-income communities.
     Improved understanding of human indoor and outdoor 
activity patterns in urban environments, especially for children.
     Improved understanding of the relationship between outdoor 
and indoor air and HAP concentrations.
     Improved monitoring to assess multipathway exposures to 
foods, such as fish, vegetables and beef, contaminated by deposition of 
urban HAPs.
    Risk assessment needs.
     Improved risk assessment methods for chemical mixtures.
    Risk management needs.
     Cost-effective control technologies for all HAPs and more 
effective controls for those HAPs posing residual risks even after 
applying currently available controls.
    Some of the major air toxic research activities currently planned 
or being undertaken by EPA include:
    Health effects and dose-response assessment research highlights.
     A proposed test rule under Toxics Substance Control Act 
(TSCA) that would require testing of 21 HAPs.
     Dose-response assessment efforts for mobile source 
pollutants (such as benzene, 1,3-butadiene, and various fuel additives, 
including

[[Page 38737]]

methylcyclopentadienyl manganese tricarbonyl (MMT)) and urban HAPs 
shown in Table 1.
     Reducing uncertainty in acute and chronic dose-response 
assessments through the use of statistical (and other) methods.
     Improved methods for identifying and quantifying the 
health effects associated with exposures to mixtures of pollutants.
     Development of a mixtures database to facilitate 
assessments involving more than one chemical.
    Emissions and exposure characterization research highlights.
     A national air toxics monitoring network.
     An updated, comprehensive emissions inventory of air 
toxics (the National Toxics Inventory).
     Various toxic emission characterization studies that 
include addressing emissions speciation for HAPs such as mercury.
     Improved nonroad and highway emission prediction models.
     Improved air quality models, including long-range 
transport models, a new model of acid deposition, and a modeling 
system, the Total Risk Integrated Methodology (TRIM), which will 
provide a framework for better assessing health and ecological risks 
from multipathway exposure to air toxic (as well as criteria) 
pollutants.
     Various exposure assessment studies and methodologies.
    Risk management research highlights.
     Identification of processes contributing to the HAP 
emissions from area source categories, and listing of control options 
and Pollution Prevention alternatives for these processes.
    In addition to those research needs and activities that will be 
identified in the Urban Report, research designed to improve 
quantitative risk assessment and management which may have relevance to 
urban HAPs, can be found in various other EPA documents. For example, 
we're developing a ``Mercury Research Strategy,'' which describes the 
key research questions for mercury that we plan to address over the 
coming 5 years. We expect that the mercury strategy will be finalized 
during 1999 (following consideration of peer review comments). A 
summary description of this and other research activities and the 
documents in which they are found will be included in a separate 
chapter of the Urban Report. As discussed earlier, we're also 
developing an ``Air Toxics Research Strategy'' that, building on the 
summary research descriptions in the Urban Report, will identify key 
research questions and the additional research that will be conducted 
to address those questions.

VI. Public Participation and Communication

A. How Will we Encourage Stakeholder Involvement?

    Because of the scope of the Strategy, we realize that various 
interests may perceive it differently. As a result, we'll make every 
effort to address the unique perspectives of the key stakeholders to 
this process, and we'll welcome their input to support an equitable 
approach to meeting our risk reduction goals. As described earlier, we 
intend to hold stakeholder meetings starting early in the next fiscal 
year to discuss State, local, and Tribal authority and implementation 
of the Strategy. With comments already received on the Strategy and 
through input from various stakeholders in these meetings, we will 
develop a plan for implementing the State, local and tribal programs. 
Below we have also provided more information on different groups that 
we plan to involve in implementing various aspects of the Strategy.
State, Local, and Tribal Governments
    National standards for mobile and major sources may not adequately 
address the human health risks in urban areas because of the combined 
emissions from these sources and the many different types of sources. 
For this reason, we expect State, local, and Tribal agencies to play an 
active role in tailoring local approaches to reduce risks in urban 
areas, and we'll ask for their help in developing practical programs to 
implement the Strategy. More information on their role is presented in 
section III.
    In a parallel effort to address the issue of roles and 
responsibilities, we'll be holding a series of meetings with State and 
Territorial Air Pollution Program Administrators and the Association of 
Local Air Pollution Control Officials (STAPPA/ALAPCO) to develop a plan 
for the most efficient and effective interaction among regulators. 
Additionally, over the next year, we plan to meet with other regulatory 
partners including Tribal leaders and city mayors to help shape the 
coordination process. In conducting urban scale assessments as 
discussed in section IV, we'll work with local communities as 
appropriate to characterize the air toxics emissions within a community 
(through monitoring and emission inventories), estimate the risks 
associated with these emissions, and identify actions which could be 
taken to reduce air toxics. We'll also explore to what extent and how 
to address air toxics indoors.
Environmental Justice Communities
    The cumulative impact of multiple emission sources on minority 
populations and low income populations in urban areas is of special 
concern. The Strategy will help identify and plan actions to decrease 
emissions that affect these communities. We're already coordinating 
with the National Environmental Justice Advisory Council (NEJAC) to 
establish mechanisms to work with communities to help solve urban air 
toxics problems. We'll work with NEJAC to explore the formation of 
groups such as round tables and panels as a means to involve 
communities, and other stakeholders, including representatives from 
universities and hospitals. These round tables/panels would explore 
issues related to rulemaking coordination, risk assessments, and the 
process of defining roles and responsibilities for Federal and State, 
local and Tribal agencies in implementing the Strategy.
Public Health Groups and Environmental Groups
    Public health concerns are a priority in this Strategy, especially 
the impact of air toxics on susceptible groups like children. We plan 
to identify and address health risks to children and seniors and 
welcome input on these key issues. We'll also encourage these groups to 
work with us on various aspects of the Strategy, such as defining the 
roles and responsibilities of State, local, and Tribal agencies.
Small Business and Industry
    Because the Strategy focuses on reducing emissions from area 
sources, impacts of the ultimate standards may be felt by small 
businesses. We'll strive, however, to ensure that regulations don't 
unfairly impact them. We also plan to involve small businesses in pilot 
projects to assess and design solutions to local air toxics risks.
    An example of how we'll provide concrete support to small 
businesses is our EPA Small Business Innovative Research (SBIR) 
Program. Under this program, we can award Phase I contracts of up to 
$70,000 over 6 months to small businesses with fewer than 500 employees 
to develop and commercialize new environmental technologies. The awards 
are based on the scientific merit and technical feasibility of the 
proposed technology. The results of Phase I determine whether the 
research idea is technically feasible, whether the firm can do high-
quality research, and whether sufficient

[[Page 38738]]

progress has been made to justify a larger Phase II effort. We can 
award Phase II contracts for up to $295,000 over 2 years to 
commercialize the technology or product. The FY2000 Phase I 
Solicitation will open on August 11, 1999 and close on October 13, 
1999. Copies of the solicitation will be posted on August 11, 1999 on 
our website at: http://www.epa.gov/ncerqa. The solicitation will also 
be available by fax at the EPA SBIR Helpline: 800-490-9194.
    In addition, large businesses could be affected by programs and 
regulations developed to implement the Strategy. As always, we'll work 
with industry representatives to try to develop technically sound, 
effective regulations that minimize the burden to affected sources.
Urban Developers
    In designing the Strategy, we've tried to avoid unfairly limiting 
the efforts of developers interested in creating business opportunities 
in urban industrial sites or areas needing revitalization. We plan to 
work with these interests to ensure that public health protection is 
achieved and economic development is encouraged.
    As with our previous air toxics regulatory development efforts, our 
efforts under the Strategy will involve stakeholders as early as 
possible in the process. We recognize that opportunities for public 
participation beyond the required notice and comment process help 
ensure we develop the most workable requirements that still achieve our 
environmental goals. We'll use the established urban air toxics 
Strategy website on the Internet (www.epa.gov/ttn/uatw/urban/
urban.pg.html) to update the public on ongoing activities and 
opportunities to participate in implementation of the Strategy. This 
will include updates on rule development, assessment activities, and 
progress toward meeting all of the Strategy goals. You can find 
information on all of our air toxics regulations at the following 
website on the Internet: www.epa.gov/ttn/uatw.

B. What is our Overall Timeline for Action?

    Many of the activities identified in the Strategy will require 
further public notice and comment, and we'll provide further 
opportunities for stakeholder input as they are developed. The public 
will also be able to measure the progress of the Strategy by tracking 
the following milestones projected in the coming five years:

 1999
    --Publish the Integrated Urban Air Toxics Strategy, including the 
urban HAPs list and the area source category list.
    --Issue the first Integrated Urban Air Toxics Strategy report to 
Congress under section 112(k)(5).
    --Complete 1996 NTI update.
    --Begin State/local/Tribal stakeholder communication and 
information exchange on implementing the Strategy.
    --Propose motor vehicle and fuel standards under section 202(l).
 2000
    --Complete initial national and urban scale assessment.
    --Complete motor vehicle and fuels standards development under 
section 202(l).
    --Start development of additional area source standards.
 2002
    --Complete 1999 NTI update.
 2003
    --Complete 1999 assessment.
    --Finalize source category list.
 2004
    --Promulgate standards for the area source categories newly listed 
in today's strategy.

    We'll attempt to meet this demanding schedule as expeditiously as 
practicable. We're currently engaged in significant efforts to develop 
standards for stationary sources that were previously listed under 
section 112(c). In addition, realistic schedule and resource 
constraints suggest that our efforts to develop additional standards 
should be phased in over time.

C. What Reports Will we Prepare To Communicate With the Public?

    We're required under section 112 of the Act to provide two reports 
to Congress on actions taken to reduce the risks to public health posed 
by the release of HAPs from area sources. The Act also requires that 
the reports identify specific metropolitan areas that continue to 
experience high risks to public health as the result of emissions from 
area sources.
    We'll submit our first report in late 1999. This report will 
provide more specific information about our Strategy, including further 
details on the methodologies we used to develop the final urban HAPs 
list and the list of source categories. The report will also provide an 
overview of previous studies conducted in various cities to 
characterize their respective urban air toxics problems and contain a 
detailed discussion of the research needed to achieve the goals of the 
Strategy. We also expect to report to the public about air toxics 
emissions trends and air quality in urban and other areas in our annual 
Air Quality and Emissions Trends Reports.

    Dated: July 6, 1999.
Robert Perciasepe,
Assistant Administrator for Air and Radiation.

Appendix A--Summary of Other Authorities, Laws, Rules, and Programs to 
Help Reduce HAP Emissions

    There are a number of other authorities, laws, rules, and 
programs that will help reduce emissions of HAPs and consequent 
exposures and risks. Some of these are discussed below. We're 
currently evaluating the appropriateness of these statutes for 
controlling emissions of HAPs as described under section 112(k)(3) 
and intend to take further actions under these statutes as 
appropriate.
    As discussed in section I., the Strategy involves collaboration 
between offices within the air program to assess the risks from 
exposures to air toxics indoors and will assimilate non-regulatory, 
voluntary programs developed to address those risks. Title IV of the 
Superfund Amendments and Reauthorization Act (SARA) provides EPA 
with the authority to perform research and provide information to 
the public on the health problems associated with air pollutants in 
the indoor environment.
    Under the Toxic Substances Control Act (TSCA), chemicals 
produced or imported into the United States are evaluated as to 
toxicity to human health and the environment. To prevent adverse 
consequences of the many chemicals developed each year, TSCA 
requires that any chemical that will reach the consumer marketplace 
be tested for possible toxic effects prior to commercial 
manufacture. Any existing chemical that is determined to pose health 
and environmental hazards is tracked and reported under TSCA. 
Procedures also are authorized for corrective action under TSCA in 
cases of cleanup of toxic materials contamination. The TSCA is a 
complementary authority to the Clean Air Act and has contributed to 
decreased emissions of several HAPs. For example, concern over the 
toxicity and persistence in the environment of polychlorinated 
biphenyl (PCB) compounds led Congress to include in TSCA 
prohibitions on the manufacture, processing, and distribution in 
commerce of PCBs (TSCA section 6(e), 15 U.S.C. 2605(e)). In 1990, 
TSCA authority was relied upon to eliminate chromium use in, and 
emissions from, comfort cooling towers (i.e., industrial process 
cooling towers used exclusively for cooling, heating, ventilation, 
and air conditioning systems).
    There are several provisions of the Resource Conservation and 
Recovery Act (RCRA) and its amendments which may yield reductions of 
urban air toxics. One impact evidenced in the 1990's is increased 
recycling and recovery of hazardous waste, including solvents which 
through volatilization contribute to HAP emissions. Section 3004(n) 
of RCRA has been the basis of a three-phased regulatory program to 
control air emissions from hazardous waste

[[Page 38739]]

treatment, storage and disposal facilities. The third phase would 
address any risks remaining after implementation of the control 
regulations issued in 1990 and 1994, which were estimated to reduce 
organic emissions by more than one million tons per year. Any 
resulting emissions and risk reductions can be considered in 
assessing progress toward the 75-percent reduction in cancer 
incidence from the baseline.
    Under the Comprehensive Environmental Response, Compensation and 
Liability Act, commonly known as Superfund, the clean-up of 
abandoned hazardous waste sites may also reduce emissions of HAPs. 
Where significant health risks from chemical releases to the air 
have been identified at Superfund sites in urban areas, clean-up 
will reduce risks from urban air toxics.
    Under the Clean Water Act (CWA), controls on the discharge of 
pollutants to surface water can also reduce the amount of HAPs 
entering the environment. These controls may take the form of 
national technology-based standards under the effluent guidelines 
program or site-specific water quality-based controls to achieve 
State water quality standards. In addition to providing control by 
establishing discharge limitations on pollutants (including HAPs) in 
the wastewater, process changes made in order to comply with these 
limitations may also reduce fugitive emission sources.
    As part of the effluent guidelines program under the CWA, we've 
issued effluent limitations for the pharmaceuticals industry. Human 
health benefits from these guidelines include reductions in excess 
cancer risk through inhalation. The regulatory impact assessment 
prepared for these guidelines estimates that the number of excess 
cancer cases avoided per year nationwide ranges from 0.02 to 0.35. 
These reductions are due to reductions in VOC emissions, including 
10 carcinogens (principally chloroform and methylene chloride). We 
can also point to air toxics benefits from the effluent guidelines 
for the pulp, paper, and particleboard industry. These regulations, 
coupled with the associated NESHAP, are expected to decrease 
background emission of HAPs by 121,200 megagrams annually.
    If a waterbody isn't meeting water quality standards even after 
all technology-based controls under the effluent guidelines program 
are in place, the State, local agency, or Tribe must list the water 
as ``water quality limited'' and prepare a ``total maximum daily 
load'' (TMDL) calculation that allocates the maximum amount of 
pollution, with a margin of safety, that the waterbody can absorb 
from point and nonpoint (including air deposited) sources. A plan 
must then be developed to implement the TMDL, which might include 
provisions to address air sources under Federal or State (or local 
or Tribal) programs. We're conducting a pilot project in two 
waterbodies to develop TMDLs identifying the relative contributions 
of mercury from various air sources. This project will also examine 
how Federal and State water programs can work together to reduce 
mercury contamination of water.
    The Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) 
provides Federal control of pesticide distribution, sale, and use. 
Several HAPs listed in Clean Air Act section 112(b) have been used 
as pesticides. An EPA registration is required of all pesticides 
sold in the United States and is intended to ensure that pesticide 
use, when in accordance with label specifications, doesn't cause 
unreasonable harm to people or the environment. It's a violation of 
FIFRA to use a pesticide in a manner inconsistent with its label. 
Registered pesticides classified as ``restricted use'' may only be 
used by registered applicators who have passed a certification exam. 
This restricted use requirement minimizes the number of persons 
having access to certain pesticides. The FIFRA regulations may also 
reduce emissions and exposures by banning (canceling or denying 
registration) or severely restricting pesticide use. Seven 
individual HAPs and members of three HAP compound groups have been 
banned or severely restricted in their use as pesticides.
    Two other Federal laws, the Emergency Planning and Community 
Right-To-Know Act (EPCRA) of 1986 and the Pollution Prevention Act 
(PPA) of 1990, while not directly regulating air emissions of HAPs, 
may influence decisions regarding chemical usage and storage, and 
yield significant reductions in air toxics risks in urban areas. The 
goal of EPCRA is to reduce risks to communities through informing 
communities and citizens of chemical hazards in their areas. 
Sections 311 and 312 of EPCRA require certain facilities to report 
the locations and quantities of chemicals stored at their facilities 
to State and local governments. This information is used by State 
and local agencies in preparing for, and responding to, chemical 
spills and similar emergencies.
    Through EPCRA, Congress mandated that a Toxics Release Inventory 
be made public. The TRI provides citizens with information about 
potentially hazardous chemicals stored, manufactured and used in 
their community. Section 313 of EPCRA specifically requires certain 
manufacturers and all Federal facilities to report to EPA and State 
governments, all releases of any of more than 600 designated toxic 
chemicals to the environment (including most of the 188 HAPs). Each 
year, more than 20,000 manufacturing facilities and 200 Federal 
facilities submit information to us on the releases of chemicals to 
the environment. We compile these data in an on-line, publicly 
accessible national database, which is a significant source of 
information regarding HAP emissions. Reporting requirements for TRI 
became more comprehensive in 1991, highlighting the importance of 
pollution prevention. In 1997 we added seven industry groups (metal 
mining, coal mining, RCRA subtitle C TSD and solvent recovery, 
petroleum distribution, electricity generating, and chemical 
distribution). We believe that for the manufacturing sector this 
public spotlight on releases and other waste management of toxic 
chemicals has led to reductions in their environmental release. 
We're also planning to lower the reporting thresholds under the TRI 
for several persistent, bioaccumulative toxic chemicals, including 
mercury and dioxin, that can cause human health and environmental 
damage at very low levels, so that additional information on 
releases will be available to the public.
    The passage of the Pollution Prevention Act (PPA) established an 
environmental hierarchy that establishes pollution prevention as the 
first choice among waste management practices. Traditionally, much 
environmental protection has involved controlling, treating or 
cleaning up pollution. Pollution prevention, which eliminates or 
minimizes pollution at the source, is most effective in reducing 
health and environmental risks because it (1) eliminates any 
pollutant associated risks, (2) avoids shifts of pollutants from one 
medium (air, water or land) to another, which can result from 
certain waste treatments, and (3) reduces waste of natural 
resources. For waste that cannot be avoided at the source, recycling 
is considered the next best option. A waste generator should turn to 
treatment or disposal only after source reduction and recycling have 
been considered. Pollution prevention strategies include redesigning 
products, changing processes, substituting raw materials for less 
toxic substances, increasing efficiency in the use of raw materials, 
energy, water, land and other techniques. The EPA implements the PPA 
by promoting voluntary pollution reduction programs, engaging in 
partnerships, providing technical assistance, funding demonstration 
projects and incorporating cost-effective pollution prevention 
alternatives into regulations and other initiatives.
    In addition, we've developed the ``Waste Minimization National 
Plan,'' a voluntary, long-term effort to reduce the quantity and 
toxicity of hazardous waste through waste minimization. The plan was 
built on extensive stakeholder involvement and was released in 1994. 
The plan focused on the following key objectives:
     Prioritize pollution prevention efforts based on risk.
     Promote source reduction over recycling.
     Adopt a multi-media approach and prevent cross media 
transfers.
     Provide flexibility in implementing pollution 
prevention activities.
     Provide accountability and measure progress.
     Involve the public.
    The plan calls for a 50-percent reduction in the presence of the 
most persistent, bioaccumulative and toxic (PBT) chemicals in 
hazardous waste by 2005.
    The starting point for selecting chemicals for the national 
waste minimization list is EPA's ``Waste Minimization Prioritization 
Tool,'' which is a software program that provides a screening-level 
assessment of the potential chronic risks that chemicals pose to 
human health and the environment, based on their persistence, 
bioaccumulative potential, and human and ecological toxicity. This 
software program contains full or partial PBT data for approximately 
4,200 chemicals. The draft ``Waste Minimization Prioritization 
Tool'' was released for public comment on June 23, 1997 (62 FR 
33868). We made significant changes in response to public comment 
and published a revised version on November 9, 1998 (63 FR 60332). 
The revised software, in conjunction with a publicly

[[Page 38740]]

reviewed methodology, was used to generate a draft list of 53 PBT 
chemicals, which is now in the process of being finalized.

[FR Doc. 99-17774 Filed 7-16-99; 8:45 am]
BILLING CODE 6560-50-P