[Federal Register Volume 68, Number 206 (Friday, October 24, 2003)]
[Notices]
[Pages 61084-61096]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-26923]



[[Page 61083]]

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Part III





Environmental Protection Agency





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Standards for the Use or Disposal of Sewage Sludge: Decision Not To 
Regulate Dioxins in Land-Applied Sewage Sludge; Notice

  Federal Register / Vol. 68, No. 206 / Friday, October 24, 2003 / 
Notices  

[[Page 61084]]


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ENVIRONMENTAL PROTECTION AGENCY

[FRL-7577-9]


Standards for the Use or Disposal of Sewage Sludge: Decision Not 
To Regulate Dioxins in Land-Applied Sewage Sludge

AGENCY: Environmental Protection Agency.

ACTION: Notice.

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SUMMARY: The U.S. Environmental Protection Agency (EPA or Agency) is 
giving final notice of its determination that neither numerical 
limitations nor requirements for management practices are currently 
needed to protect human health and the environment from reasonably 
anticipated adverse effects from dioxin and dioxin-like compounds in 
land-applied sewage sludge.

DATES: In accordance with 40 CFR 23.2, this final decision is 
promulgated for purposes of judicial review as of 1 p.m. Eastern Time 
on November 7, 2003. Under section 509(b)(1) of the Clean Water Act, 
judicial review of this final action can be obtained only by filing a 
petition for review in the United States Court of Appeals within 120 
days after the final action is considered promulgated for purposes of 
judicial review.

FOR FURTHER INFORMATION CONTACT: Robert Cantilli, U.S. Environmental 
Protection Agency, Office of Water, Office of Science and Technology, 
Health and Ecological Criteria Division (4304T), 1200 Pennsylvania 
Avenue, NW., Washington, DC 20460 (202) 566-1091. 
[email protected].

SUPPLEMENTARY INFORMATION: 

A. Interested Entities

    Entities typically regulated by Standards for the Use or Disposal 
of Sewage Sludge are those that prepare sewage sludge (also called 
``biosolids'') and/or use or dispose of the sewage sludge through 
application to the land, placement in a surface disposal unit, or 
incineration in a sewage sludge incinerator. Entities potentially 
interested by today's notice include those that prepare and/or use 
sewage sludge for land-application purposes. Categories and entities 
interested in today's action include:

------------------------------------------------------------------------
                Category                  Examples of affected entities
------------------------------------------------------------------------
State/Local/Tribal Government..........  Publicly owned treatment works
                                          and other treatment works that
                                          treat domestic sewage, prepare
                                          sewage sludge, and/or apply
                                          sewage sludge to the land.
Federal Government.....................  Federal Agencies with treatment
                                          works that treat domestic
                                          sewage, prepare sewage sludge,
                                          and/or apply sewage sludge to
                                          the land.
Farmers and ranchers...................  Individuals who apply sewage
                                          sludge to land.
Industry...............................  Privately-owned treatment works
                                          that treat domestic sewage,
                                          and persons who receive sewage
                                          sludge and change the quality
                                          of the sewage sludge before it
                                          is applied to the land.
------------------------------------------------------------------------

This table is not intended to be exhaustive, but rather provides a 
guide for readers regarding entities likely to be interested in this 
action. This table lists the types of entities that EPA is now aware 
could potentially be interested in this action. Other types of entities 
not listed in the table could also be interested. To determine whether 
your facility is affected by this action, you should carefully examine 
today's notice. If you have questions regarding the applicability of 
this action to a particular entity, consult the person listed in the 
preceding FOR FURTHER INFORMATION CONTACT section.

B. How Can I Get Copies of This Document and Other Related Information?

    1. Docket. EPA has established an official public docket for this 
action under Docket ID No. OW-2002-0019. The official public docket 
consists of the documents specifically referenced in this action, any 
public comments received, and other information related to this action. 
Although a part of the official docket, the public docket does not 
include Confidential Business Information (CBI) or other information 
whose disclosure is restricted by statute. The official docket is the 
collection of materials that are available for public viewing at the 
Water Docket in the EPA Docket Center, (EPA/DC) EPA West, Room B102, 
1301 Constitution Ave., NW., Washington, DC. The EPA Docket Center 
Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through 
Friday, excluding legal holidays. The telephone number for the Public 
Reading Room is (202) 566-1744, and the telephone number for the Water 
Docket is (202) 566-2426.
    2. Electronic Access. You may access this Federal Register document 
electronically through the EPA Internet under the ``Federal Register'' 
listings at http://www.epa.gov/fedrgstr/.
    An electronic version of the public docket is available through 
EPA's electronic public docket and comment system, EPA Dockets. You may 
use EPA Dockets at http://www.epa.gov/edocket/ to view public comments, 
access the index listing of the contents of the official public docket, 
and to access those documents in the public docket that are available 
electronically. Once in the system, select ``search,'' then key in the 
appropriate docket identification number. Although not all docket 
materials may be available electronically, you may still access any of 
the publicly available docket materials through the docket facility 
identified in section B.1.

C. Table of Contents

I. Abbreviations and Acronyms Used
II. What Is the Legal History of the Standards for the Use and 
Disposal of Sewage Sludge?
III. What Did EPA Propose for Dioxins in Land-Applied Sewage Sludge?
    A. Proposed Rule
    B. Notice of Data Availability (NODA)
IV. What Final Action Is EPA Taking Today?
V. What is the Basis for This Final Action for Dioxins in Land-
Applied Sewage Sludge?
    A. Overview
    B. Assessment of Cancer Risk From Dioxins in Land-Applied Sewage 
Sludge
    C. Findings Concerning Ecological Effects
    D. Indications From the 2001 Survey of Dioxins in Sewage Sludge
VI. Environmental Justice
VII. Discussion of Scientific Information Presented in the NODA
    A. Assessing Cancer Risk
    B. Assessing Non-Cancer Risk
VIII. Public Comments and Other Considerations
    A. Definition of ``Dioxins''
    B. The Need for Regulating Dioxins in Land-Applied Sewage Sludge
    C. Groundwater Exposure
    D. Synergistic Effects
    E. Voluntary Program
IX. List of References

I. Abbreviations and Acronyms Used

AMSA--Association of Metropolitan Sewerage Agencies
CFR--Code of Federal Regulations

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CWA--Clean Water Act
DMT--dry metric tons
EFH--Exposure Factors Handbook
EMS--Environmental Management System
EPA--U.S. Environmental Protection Agency
HQ--hazard quotient
HEI--highly exposed individual
LADD--lifetime average daily dose
MGD--million gallons per day
NBP--National Biosolids Partnership
ng TEQ/kg--nanograms toxic equivalence per kilogram body weight
NODA--Notice of Data Availability
NSSS--National Sewage Sludge Survey
PCBs--polychlorinated biphenyls
PCDDs--polychlorinated dibenzo-p-dioxins
PCDFs--polychlorinated dibenzofurans
pg TEQ/day--picograms toxic equivalence per day
pg TEQ/kg-d--picograms toxic equivalence per kilogram body weight per 
day
POTWs--Publicly Owned Treatment Works
ppt--parts per trillion
Q1*--cancer slope factor
RfD--reference dose
SAB--Science Advisory Board
SERA--screening ecological risk analysis
TBD--Technical Background Document
TCDD--2,3,7,8-tetrachlorodibenzo-p-dioxin
TEF--toxicity equivalency factor
TEQ--toxic equivalence
WHO--World Health Organization

II. What Is the Legal History of the Standards for the Use or Disposal 
of Sewage Sludge?

    EPA promulgated Standards for the Use or Disposal of Sewage Sludge 
(40 CFR part 503) under section 405(d) and (e) of the Clean Water Act 
(CWA), 33 U.S.C. 1345(d), (e), as amended by the Water Quality Act of 
1987. In these amendments to section 405 of the CWA, Congress, for the 
first time, set forth a comprehensive program for reducing the 
potential environmental risks and maximizing the beneficial use of 
sewage sludge. As amended, section 405(d) of the CWA requires EPA to 
establish numerical limitations and management practices, when 
appropriate, that protect public health and the environment from the 
reasonably anticipated adverse effects of toxic pollutants in sewage 
sludge. Section 405(e) prohibits any person from disposing of sewage 
sludge from a publicly owned treatment works (POTWs) or other treatment 
works treating domestic sewage for any use except in compliance with 
regulations promulgated under section 405.
    Section 405(d) calls for two rounds of sewage sludge regulations 
and sets deadlines for promulgation. In the first round, EPA was to 
establish numerical limits and management practices for those toxic 
pollutants which, based on ``available information on their toxicity, 
persistence, concentration, mobility, or potential for exposure, may be 
present in sewage sludge in concentrations which may adversely affect 
public health or the environment.'' CWA section 405(d)(2)(A). The 
second round is to address toxic pollutants not regulated in the first 
round ``which may adversely affect public health or the environment.'' 
CWA section 405(d)(2)(B).
    EPA did not meet the timetable in section 405(d) for promulgating 
the first round of regulations, and a citizen's suit was filed to 
require EPA to fulfill this mandate, (Gearhart v. Reilly, Civ. No. 89-
6266-HO (D. Ore.)). A consent decree was entered by the court in that 
case, establishing schedules for both rounds of sewage sludge rules. 
EPA promulgated the first rule, codified at 40 CFR part 503, in 1993 at 
58 FR 9248 (February 19, 1993) (``Round One''). For the second round 
(``Round Two''), EPA identified 31 pollutants and pollutant categories 
not regulated in Round One that EPA was considering for regulation. In 
November 1995, EPA narrowed the original list of 31 pollutants to 
polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated 
dibenzofurans (PCDFs) and dioxin-like coplanar polychlorinated 
biphenyls (PCBs) for the second round of rulemaking (USEPA, 1996). The 
consent decree required the Administrator to sign a notice for 
publication proposing Round Two regulations no later than December 15, 
1999, and to sign a notice taking final action on the proposal no later 
than December 15, 2001.
    On December 15, 1999, the Administrator signed a proposal to 
establish numerical limits for dioxins, dibenzofurans, and co-planar 
PCBs (``dioxins'') in sewage sludge that is applied to the land and 
proposed not to regulate dioxins in sewage sludge that is disposed of 
in a surface disposal unit or fired in a sewage sludge incinerator 
(December 23, 1999, 64 FR 72045). On December 15, 2001, the 
Administrator signed a final notice of EPA's determination that 
numerical limitations or management practices are not warranted for 
dioxins in sewage sludge that are disposed of in a surface disposal 
unit or incinerated in a sewage sludge incinerator (66 FR 66228). In 
that notice, EPA also announced that a final action on the Round Two 
proposal to amend the Standards for the Use or Disposal of Sewage 
Sludge for sewage sludge that is applied to the land would be published 
at a later date. The consent decree in Gearhart was amended to extend 
the deadline for final action on the land application Round Two 
rulemaking from the original date of December 15, 2001, to a new date 
of October 17, 2003.
    On June 12, 2002, EPA published a Notice of Data Availability 
(NODA) containing new information relating to dioxins in land-applied 
sewage sludge and requested public comments (67 FR 40554). The NODA 
provided a revised cancer risk assessment for dioxins in land-applied 
sewage sludge, newly collected data regarding concentration of dioxins 
in sewage sludge, and a new ecological screening risk analysis and 
solicited public comments.

III. What Did EPA Propose for Dioxins in Land-Applied Sewage Sludge?

A. Proposed Rule

    EPA proposed a numeric limitation of 300 part per trillion (ppt) 
for ``dioxins'' measured as toxic equivalence (TEQ) in land-applied 
sewage sludge, and related monitoring, record-keeping and reporting 
requirements. EPA proposed a definition of ``dioxins'' to mean 29 
specific congeners of PCDDs, PCDFs, and coplanar PCBs that have been 
found in sewage sludge. The proposed definition of ``dioxins'' 
specified seven 2,3,7,8-substituted congeners of PCDDs, ten 2,3,7,8-
substituted congeners of PCDFs, and twelve coplanar PCB congeners.
    The December 1999 proposal included a monitoring schedule for 
dioxins in land-applied sewage sludge that would have required 
wastewater treatment plants to monitor for dioxins in their sewage 
sludge for two consecutive years. EPA also proposed a modified 
frequency of monitoring based on analytical results from the first two 
years of monitoring.
    EPA also proposed to exclude from the proposed numeric limit and 
monitoring requirements those treatment works having a flow rate equal 
to or less than one million gallons per day (MGD) and certain sewage 
sludge-only entities that receive sewage sludge for further processing 
prior to land application. This proposed exclusion was based on the 
relatively small amount of sewage sludge that is prepared by these 
facilities and entities and, therefore, the low probability that land 
application of these materials could significantly increase risk from 
dioxins to human health or the environment.
    EPA's proposal was based on a deterministic risk assessment and 
data regarding dioxins in sewage sludge

[[Page 61086]]

collected in the 1988-1989 National Sewage Sludge Survey (NSSS). See 64 
FR 72045, 72048-72051 (December 23, 1999) and the National Sewage 
Sludge Survey (USEPA, 1990) for a full discussion of the proposed rule 
and supporting documentation.
    In addition, unrelated to dioxins in sewage sludge, EPA proposed 
technical amendments to the frequency of monitoring requirements for 
pollutants other than dioxins. These amendments were intended to 
clarify but, with one exception, not alter the monitoring schedule in 
the existing sewage sludge rule. The one exception would require 
preparers of material derived from sewage sludge to determine the 
appropriate monitoring schedule based on quantity of material derived 
rather than quantity of sewage sludge received for processing.

B. Notice of Data Availability (NODA)

    Based on comments critical of both the proposal's use of a 
deterministic risk assessment and its use of more than decade-old data 
on dioxins concentrations in sewage sludge, in 2001 EPA collected and 
analyzed samples of sewage sludge nationwide in order to obtain new 
information on the levels of dioxins in sewage sludge. EPA also 
substantially revised the cancer risk assessment for dioxins associated 
with land application of sewage sludge. EPA used new dioxins 
concentration data in the revised risk assessment and conducted 
statistical analyses to better understand the fluctuation of dioxins 
concentrations in sewage sludge samples over time. In the NODA, EPA 
summarized the new sewage sludge data, the revised risk assessment, and 
presented an approach to assess potential non-cancer health effects of 
exposure to dioxins associated with land application of sewage sludge. 
EPA also presented a screening ecological risk analysis (SERA) of the 
effects of dioxins in land-applied sewage sludge on ecological species. 
EPA requested comments on the new data and risk analyses, additional 
dioxins exposure information, and comments on any impact the data and 
information might have on the 1999 proposed rule with respect to land 
application of sewage sludge. EPA also requested comment on whether 
monitoring requirements to measure dioxins in land-applied sewage 
sludge should be promulgated in lieu of a numerical limitation.
    In the NODA, EPA also presented information from EPA's draft dioxin 
reassessment document, Exposure and Human Health Reassessment of 
2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds. EPA 
described implications of the draft dioxin reassessment for the final 
determination regarding regulation of dioxins in land-applied sewage 
sludge and requested public comment. EPA included this information in 
the NODA in order to be in a position to fulfill its obligations under 
the Gearhart v. Whitman consent decree. The consent decree requires EPA 
to take final action on or before October 17, 2003, regardless of 
whether EPA issues a final dioxin reassessment document, with some 
schedule adjustment allowed depending on the timing of EPA's issuance 
of a final dioxin reassessment document prior to October 17, 2003. EPA 
has not issued a final dioxin reassessment document; thus, the October 
17, 2003 deadline applies. Regarding the draft dioxin reassessment 
documents discussed in the NODA, EPA has continued to revise these 
documents, and the science continues to be under review. Review by the 
National Academy of Sciences is the next review to be undertaken, as 
specified by Congress in the Conference Report accompanying EPA's 
fiscal year 2003 appropriation. H.R. Conf. Rep. No. 108-10, at 1445-46 
(2003).

IV. What Final Action Is EPA Taking Today?

    EPA has determined that no further regulation of land-applied 
sewage sludge is needed to protect public health and the environment 
from reasonably anticipated adverse effects from exposure to dioxins in 
land-applied sewage sludge. Therefore, no numeric limitations, 
monitoring, operational standards, or management practices are being 
established in 40 CFR part 503 for dioxins in land-applied sewage 
sludge.
    While monitoring data could be useful to a local community to 
discover whether a significant increase is occurring in the dioxin 
concentration and assist in identifying the source of any such 
significant increase (see later discussion), the data indicate that 
such increases are short-term in nature, and the risk assessment 
showing low risk to the HEI takes these spikes into account. Therefore, 
EPA has determined that monitoring in lieu of a numerical limit is not 
warranted.
    With respect to revisions to the existing requirements pertaining 
to frequency of monitoring of pollutants other than dioxins in land-
applied sewage sludge, EPA is not taking final action at this time. 
Therefore, any comments on the proposed amendment to the footnote to 
Table 1 in 40 CFR 503.16 are not being addressed today. EPA may take 
final action on this proposed amendment in a subsequent rulemaking.

V. What Is the Basis for This Final Action for Dioxins in Land-Applied 
Sewage Sludge?

A. Overview

    Sewage sludge is a residual mixture of solids and water as a result 
of wastewater treatment. Generally, sewage sludge consists of 2 to 28 
percent solids in a water matrix. The solids component of sewage sludge 
typically contains microbial residue, microbes and trace quantities of 
chemicals such as metals and organic compounds, including dioxin and 
dioxin-like compounds. In the United States, approximately 8 million 
dry metric tons (DMT) of sewage sludge are produced annually by 16,000 
wastewater treatment plants. Approximately 54 percent (4.32 million 
DMT) are applied to land to fertilize and condition soils; 28 percent 
(2.24 million DMT) are disposed of at municipal solid waste landfills; 
17 percent (1.36 million DMT) are incinerated; and 1 percent (0.08 
million DMT) is disposed of in lagoons or sewage sludge-only landfills. 
Of the total amount land-applied, an estimated 85 percent (3.7 million 
DMT) are applied to agricultural lands used to raise crops for human or 
animal consumption. Sewage sludge is applied to some 0.1 percent of 
available agricultural land in the United States. Other land 
application sites include forests, reclamation sites such as strip 
mines, and public-contact sites, such as parks, golf courses, highway 
median strips, and lawns.
    EPA has decided not to regulate dioxins in land-applied sewage 
sludge because EPA considers the predicted risks to human health and 
the environment from dioxin and dioxin-like compounds in land-applied 
sewage sludge to be low. Based on recently collected data and 
assessment of risk, EPA has concluded that the existing regulation of 
sewage sludge in 40 CFR part 503 is adequate to protect human health 
and the environment from the reasonably anticipated adverse effects of 
dioxins in land-applied sewage sludge.
    Risk is determined based on both toxicity and exposure. Regarding 
toxicity, dioxins have been shown to elicit both cancer and a variety 
of non-cancer effects in animals, and there is strong evidence to 
indicate that humans are susceptible to the same toxic effects. 
Although dioxins are found in extremely small quantities in water and 
soil, they persist in the environment and accumulate in the food chain. 
However, regarding exposure, EPA's evaluation of the effects on human 
health due to

[[Page 61087]]

exposure to dioxins in land-applied sewage sludge shows the risks to be 
minimal.
    This evaluation looked at the segment of the U.S. population that 
EPA identified as the most exposed to dioxins in land-applied sewage 
sludge: farmers (and their families) who apply sewage sludge to their 
land and consume a high percentage of their own products. This 
population was selected in part because of their proximity to the land 
where sewage sludge is applied and, more importantly, because of the 
portion of their diet grown on land where sewage sludge is applied. 
EPA's risk assessment shows that even these ``highly exposed 
individuals'' (HEI) are at low risk of cancer from dioxins in land-
applied sewage sludge.
    The risk assessment analyzed cancer risk from exposure to dioxins 
in land-applied sewage sludge. The risk assessment predicted an excess 
lifetime cancer risk to members of the highly exposed farm family that 
is in the range of cancer risks that does not warrant additional 
regulation of land-applied sewage sludge. Indeed, the number of cancer 
cases for this farm family population is extremely low, less than one 
cancer case per year.
    Because the general population of the U.S. has lower exposure to 
dioxins from land-applied sewage sludge than the modeled farm family, 
the incremental cancer risk from exposure to dioxins in land-applied 
sewage sludge for the general population (i.e., those not members of a 
highly exposed farm family) is lower than the risk to the HEI. 
Therefore, having found that the existing sewage sludge land-
application regulations (e.g., grazing restrictions, agronomic rate 
application limitation) are adequate to protect the highly exposed 
population from the cancer risks due to dioxins in land applied sewage 
sludge, EPA concludes that the existing regulations are adequate to 
protect the general population, which is subject to lower exposures.
    With respect to non-cancer effects, EPA does not yet have a method 
to calculate the non-cancer risks that may occur to either the highly 
exposed modeled population or the general population. EPA used a model 
to predict the increased dioxin body burden over prolonged exposure to 
dioxins in land-applied sewages sludge. However, in the absence of an 
acceptable daily dose for dioxins (also referred to also as a reference 
dose, or RfD) or other measurement, EPA is not able to estimate the 
potential development of non-cancer effects in the modeled HEI 
population from the increases in dioxins body burdens. See section 
VII.B. for a discussion of the evolving science with respect to 
assessing non-cancer health risks from exposure to dioxins.
    EPA also performed a Screening Ecological Risk Analysis (SERA) on 
the risks to wildlife due to exposure to dioxins from land-applied 
sewage sludge. The screen calculated the ratio of estimated doses of 
dioxins to wildlife as a result of the land application of sewage 
sludge to acceptable dioxin doses to wildlife (dioxin wildlife 
benchmarks). While not definitive risk estimates, the results of the 
SERA indicate that wildlife species should not be significantly 
impacted by dioxins in land-applied sewage sludge.
    In addition, the results of EPA's 2001 Dioxin Update to the 
National Sewage Sludge Survey (USEPA, 2002b) indicate that dioxin 
levels in sewage sludge have declined since 1988, the last time that 
dioxins in sewage sludge were surveyed by EPA. There is reason to 
believe that this downward trend in dioxin concentration in sewage 
sludge will continue as additional regulatory controls are placed on 
additional sources of dioxin creation, especially on various types of 
combustion practices and their emissions, as well as effluent 
limitation guidelines for the pulp, paper, and paperboard point source 
category, 40 CFR part 430.
    In summary, the information available today on dioxin exposures, 
toxicity and assessed cancer risks supports EPA's determination that no 
additional numeric limits or management practices are required to 
adequately protect human health and the environment from the adverse 
effects of dioxins in land-applied sewage sludge.

B. Assessment of Cancer Risk From Dioxins in Land-Applied Sewage Sludge

    As EPA stated in the proposal and the NODA, EPA is basing its 
decision with respect to human health impacts on an assessment of the 
risk of cancer due to exposure to dioxins in land-applied sewage 
sludge. Both the risk assessment for the proposed rule and the revised 
risk assessment presented in the NODA were based on EPA's 
identification of cancer as the hazard to be assessed.
    1. Redefinition of the HEI and Assumptions Regarding the HEI: For 
the December 1999 proposal, EPA modeled a ``rural family'' as the 
Highly Exposed Individual (HEI) population. In the 1999 risk 
assessment, EPA assumed that the modeled rural family's risk of adverse 
health effects resulting from exposure to dioxins in land-applied 
sewage sludge is greater than that of the general population because a 
higher percentage of the family's diet consists of food grown on sewage 
sludge-amended soil. At proposal, the rural family was assumed to 
consume 10 percent of their beef, beef liver, and lamb diet, three 
percent of their dairy diet, and 43-59 percent of their produce diet 
from crops raised on sewage sludge-amended soil (64 FR 72053).
    In contrast, the revised risk assessment conducted in support of 
the final decision used a probabilistic method (Monte Carlo) to produce 
an estimate of the distribution of risk to the HEI. In general, the 
probabilistic risk assessment approach better characterizes the range 
of potential risks, and better accounts for uncertainty and 
variability. For the revised risk assessment, EPA retained the basic 
assumption from the proposal that the modeled HEI population is at 
greater risk than the general population. However, EPA revised a number 
of the exposure assumptions with respect to the modeled HEI population.
    In the revised risk assessment, EPA assumed that members of the 
highly exposed farm family live on farms where sewage sludge is land-
applied as fertilizer or a soil amendment on pasture land as well as 
crop land. In addition, in the revised risk assessment EPA assumed that 
a higher percentage of the farm family's diet consists of food grown on 
sewage sludge-amended soil. Specifically, EPA assumed that the farm 
family consumes 49 percent of the beef and 25.4 percent of the dairy 
products in their diet from products of their own farms. EPA also 
assumed, for the first time, that the adults on the farm consume fish 
caught from a nearby waterbody (stream) pond. As in the deterministic 
risk assessment, the revised risk assessment assumed that the farm 
family also raised a significant portion of its fruit and vegetable 
diet on sewage sludge amended soils. A description of the modeled HEI 
population and how its risk was estimated is presented in the 
Background Document, Standards for Use or Disposal for Sewage Sludge, 
Final Action (USEPA, 2003b).
    In the NODA, EPA requested comments on the Agency's use of the farm 
family scenario described for the revised risk assessment. A few 
commenters agreed with EPA's definition of the HEI population as the 
farm family. Most commenters believed that EPA's hypothetical farm 
family risk scenario was unrealistic and would overestimate risk. They 
argued that no family would farm its land in the manner described, nor 
consume such a high percentage of food (up to 50 percent) grown on 
sewage sludge-amended land. They also believed it

[[Page 61088]]

unlikely that every farm in America has a fish pond receiving dioxins 
runoff from land-applied sewage sludge. A few other commenters believe 
that EPA's assumptions were not sufficiently conservative, for example, 
that the percentage of home grown food in the diet was too low. 
Comments concerning the HEI also said that the risk assessment did not 
consider the possibility that farmland would be developed and that 
houses or schools could be built on farmland.
    EPA disagrees with comments that assumptions for the modeled HEI 
population are too conservative and should be changed. Regarding the 
comment that the amount of food grown on sludge-amended land consumed 
by farm families as modeled in the revised risk assessment is too 
conservative, EPA disagrees. The values that EPA used to estimate the 
proportion of the farmer's diet that is home produced were taken from 
Table 13-71 (Fraction of Food Intake that is Home Produced) of the 
Exposure Factors Handbook (USEPA, 1997), a peer reviewed source of data 
for use in risk assessments. For similar reasons, EPA also disagrees 
with comments that EPA's estimates of home grown food consumption are 
not sufficiently conservative. In addition, as some commenters pointed 
out, the risk assessment should model the ``reasonably maximum 
exposed'' individual. EPA believes that the HEI modeled in the risk 
assessment meets this description, and that ``reasonably maximum 
exposed'' is not equivalent to ``maximum exposed.'' Although one could 
conceive of the possibility that someone may consume up to100% percent 
of their diet from home grown products, EPA does not believe it is 
reasonable to use this assumption in the risk assessment.
    One commenter stated that houses could be built on farmland in the 
future and that EPA should factor this in (presumably to address 
families living on sewage sludge amended soil). However, because the 
risks associated with the scenario that EPA evaluated (the farm family 
as the highly exposed population) are greater than the risks EPA would 
estimate for a residential land use scenario, there is no need for EPA 
to evaluate residential exposure. In addition, the Agency evaluated the 
risks associated with a child's ingestion of sewage sludge amended 
soil, which could be typical of a residential scenario. Those risks are 
lower than those for a child's ingestion of contaminated beef and dairy 
products as in the modeled farm family described herein. (USEPA, 
2003a).
    Another commenter stated that it is unreasonable to assume that 
every farm has a fish pond receiving dioxins from runoff of land-
applied sewage sludge. Fish consumption by an adult recreational fisher 
on the farm was one of the pathways used in the exposure model. EPA 
agrees that while it is unlikely that every farm will have a waterbody 
from which fish are caught and consumed, it is a possible scenario and 
a valid one to include in the analysis. In any case, the risk 
assessment indicates that the consumption of fish from a stream 
receiving dioxins runoff in land-applied sewage sludge results in 
minimal influence on the risk estimate.
    2. Other Assumptions in the Risk Assessment: In addition to the 
revised modeled HEI population assumptions (USEPA, 2003a), other 
assumptions were used in the revised risk assessment. Again, these 
assumptions, to the extent possible, are presented as a range of 
values, which were modeled using a Monte Carlo probabilistic method. A 
number of assumptions concern farming practices and sewage sludge 
application rates. For sewage sludge application rates, EPA assumed a 
distribution ranging from 5 to 10 metric tons of sludge per hectare 
applied every other year for a period of time ranging from once to 40 
years (that is, EPA assumed that there would be from one to 20 
applications of sewage sludge). Half the acreage on the modeled farm 
was assumed to be in tilled crop production and half permanently in 
untilled pasture. EPA assumed that row crops are tilled three times per 
year, and that tilling incorporates sewage sludge into the top 20 cm of 
soil. EPA assumed that sewage sludge that is applied to pasture is not 
tilled. We used these assumptions because they are typical of 
agricultural application situations for soil amendment products by 
convention.
    Many of the assumptions and values used in the revised risk 
assessment differed from those in the 1999 risk assessment for the 
proposed rule. The revised risk assessment includes new exposure 
pathways and mechanisms to more accurately portray farm conditions for 
the modeled HEI population. For example, the 1999 risk assessment 
assumed that pastured animals only eat sewage sludge-amended soil 
containing dioxins; this was assumed to be the animals' only route of 
exposure. In contrast, the revised risk assessment assumed that cattle 
ingest dioxins from several sources: leaf surfaces containing dioxins 
volatilized from the top two centimeters of soil; sewage sludge 
particles that remain on the leaf surfaces; and direct ingestion of 
sewage sludge-containing soil. The revised risk assessment also 
included chickens and assumed that they ingest soil from a buffer area 
that receives dioxins through erosion of surface soils from adjacent 
sewage sludge-amended pasture and crop.
    EPA requested comments on the specific assumptions outlined in the 
revised risk assessment, and received a variety of public comments. 
Some commenters believed that these assumptions, like those concerning 
the HEI, were too conservative and reflected a worst-case scenario. 
Others wanted EPA to evaluate additional exposure pathways and 
scenarios (i.e., dermal exposure, risks for breast-fed infants combined 
with risks for child and adult receptors, and soil ingestion rates that 
reflect potentially different soil contact behavior for crops and 
pasture). Other commenters believed EPA underestimated risk of cancer 
from exposure to dioxins in land-applied sewage sludge. EPA received 
several comments on the conceptual site models and exposure scenarios. 
These comments included statements that the risk assessment did not 
account for harvesting and land-use restrictions, or variation in 
sludge application rates among different crops and regions. Other 
commenters stated that modeling assumptions such as the HEI modeled 
farm family being exposed to dioxins from multiple pathways were 
questionable (uncertainty inherent in application of models and use of 
many ``average'' values imbedded in the assessment) and the vapor 
dispersion model may underestimate vapor concentration.
    The revised risk assessment for dioxins in land-applied sewage 
sludge does not include additional exposure pathways, however, EPA has 
summed the risk from all pathways to estimate the overall risk to a 
given receptor. As explained later in this notice, EPA evaluated the 
risks to the adult, child, and nursing infant in the farm family. In 
addition to ingestion of breast milk for the infant, the risk 
assessment evaluated up to six additional exposure pathways and 
exposure routes: (1) Inhalation of ambient air; (2) incidental 
ingestion of soil in the buffer; (3) ingestion of above- and below-
ground produce grown on the crop land; (4) ingestion of beef and dairy 
products from the pasture; (5) ingestion of home produced poultry and 
eggs from the buffer; and (6) ingestion of fish from the nearby 
waterbody. More detailed descriptions of the revised risk assessment 
assumptions and methodologies are presented in the TBD, Section 5.

[[Page 61089]]

    No data were available on the variation in sludge application rates 
for specific crops or regions. Had these data been available, they 
could have been considered in the analysis. In the revised 
probabilistic risk assessment, however, EPA placed the conceptual farm 
scenario in 41 different meteorological and agricultural soil regions 
in the U.S. to account for variations in different crop harvesting and 
land use restrictions. The analysis as conducted is conservative and 
the risks estimated using these conservative use assumptions for the 
crops requiring the greatest fertilizer application still demonstrate 
low risks to even the HEI (members of a farm family that apply sewage 
sludge to their own land and consume products from their land).
    EPA disagrees with comments that the risk assessment does not 
appropriately consider volatilization of dioxins from sewage sludge. 
First, the equations that EPA used (USEPA, 2003a) to represent the 
sewage sludge's environmental fate and transport in soil included 
volatilization as a fate and transport mechanism. While EPA assessed 
volatilization as a dioxin transport mechanism for several exposure 
pathways, volatilization is an important component only for the 
critical pathway of the contamination of forage crops grown on the 
agricultural field with subsequent ingestion of these crops by beef and 
dairy cattle. This is so because volatilization is the main mechanism 
of dioxin transport from the sewage sludge soil mixture to the 
receiving surfaces of the forage crop, which is a component of the 
mechanism of dioxin exposure to grazing animals. Volatilization of 
dioxins via other exposure pathways does not significantly contribute 
to the exposure of dioxins to the HEI.
    To address the vapor concentration question (i.e., dioxins 
concentrations on the surfaces of forage crops), the mixing height 
values used in this analysis are contained in the Industrial Source 
Complex Short-Term Model, Version 3 (ISCST3), the air model used in 
this analysis. This is an approved method for modeling area sources 
such as agricultural fields. This model has been validated with 
measurement data and is less conservative than the box model used in 
the proposed rule, which did not include dispersion and deposition of 
sewage sludge. A conservative modeling assumption is that land applied 
sewage sludge remains in the top two centimeters (cm) of the receiving 
soil for the pasture where the animals are grazed. This is an unlikely 
assumption since weathering and natural soil organism (e.g. earthworms) 
activity would naturally incorporate the sewage sludge into the soil at 
greater depths. This assumption creates an upper end dioxin transport 
from the sewage sludge soil mixture to the surface of the forage crop.
    3. Cancer Slope Factor (Q1*): The cancer slope factor is used to 
calculate the incremental cancer risk attributable to the exposure to a 
pollutant. The cancer slope factor (also referred to as Q1*) is a 
numeric value which relates the incremental probability of developing 
cancer from exposure to a particular substance. The cancer slope factor 
is expressed as excess lifetime cancer risk per unit exposure, and is 
usually quantified in terms of milligrams or picograms toxic 
equivalents of substance per kilogram of body weight/day ((pg TEQ/kg-
d)-\1\). The greater the numeric value of the cancer slope, 
the greater the carcinogenic potency of the substance. For example, 1 x 
10-\5\ is greater than the numeric value 1 x 
10-\6\. The same slope factor is used to estimate cancer 
risk for both children and adults. The cancer slope factor represents 
the upper bound 95th percentile confidence limit of the excess cancer 
risk from a lifetime exposure to a pollutant (i.e., the dose for which 
increased risk of cancer is predicted for the most sensitive five 
percent of the population).
    For calculating cancer risk from exposure to dioxins, in the 
revised risk assessment EPA used a cancer slope factor for TCDD of 1.56 
x 10-\4\ picrograms toxic equivalence/kilogram body weight/
day ((pg TEQ/kg-d)-\1\) (USEPA, 1985). Thus, the estimate 
for the 95th percentile excess lifetime cancer risk to the modeled HEI 
population (i.e., the five percent of the HEI population that is most 
exposed) is 2 x 10-\5\, or 2 in 100,000.
    Cancer risk can also be expressed in terms of the number of 
additional cases of cancer annually attributable to exposure to dioxins 
in land-applied sewage sludge. This requires an estimation of the 
number of people in the United States that fall into the farm family 
scenario that EPA modeled. As explained in the NODA (67 FR 40554) 
population could be no more than some 11,000 people. By assuming that 
all sewage sludge produced in the U.S. is land-applied, and by 
including all farm families whose diets consist of 50 percent of 
products produced on their farms, EPA took the approach of calculating 
a very high estimate of the size of the highly exposed population. A 
more realistic estimate of the HEI population takes into account the 
fact that only about half of the sewage sludge produced in the U.S. is 
land applied, and that the number of individuals who consume both home-
grown dairy and beef can, by definition, be no greater than the smaller 
of the number of individuals who consume either home-produced dairy or 
home-produced beef. This approach results in an estimate of 1,600 
persons in the HEI population, which is number of persons estimated to 
consume home-produced diary products. Because it is unlikely that all 
of those who consume home-produced dairy products also graze their 
dairy cows on sewage sludge-amended pastures, even this number may 
overestimate the size of the highly exposed population. See Background 
Document, USEPA, 2003b for a detailed explanation of calculating the 
HEI population. In order to present both the more realistic evaluation 
as well as a high estimate of the number of excess cancer cases in this 
population attributable to exposure to dioxins in land-applied sewage 
sludge, EPA calculated these estimates as a range.
    Using this range of 1,600 to 11,200 individuals in the HEI 
population, EPA estimates that there could be between 0.002 to 0.01 
total excess cancer cases in the HEI populations attributable to land 
application of sewage sludge. This corresponds to additional annual 
cancer cases of between 0.00003 and 0.0001 that would be attributable 
to land application of sewage sludge. Thus, whether the HEI population 
in the U.S. is estimated to be some 1,600 individuals or 11,200 
individuals, or whether the maximum 95th percentile or more accurate 
50th percentile risk is used, the number of excess lifetime cancer 
cases attributable to dioxins in land-applied sewage sludge approaches 
zero. EPA's methodology for reaching this estimate is explained as 
follows:
    EPA estimates individual excess lifetime cancer risk as the product 
of an individual's lifetime average daily dose (LADD) of dioxins 
(expressed as a TEQ) and the cancer slope factor for TCDD (see Table 
1). EPA summed individual exposure and subsequent cancer risks from all 
pathways relevant to an exposed individual to estimate the total 
individual lifetime cancer risk from all pathways. The estimate of the 
total number of lifetime cancer cases expected within a population is 
the product of the individual excess lifetime cancer risk estimates for 
all individuals in the population and the number of individuals in the 
population. Because this estimate looks at the HEI population as a 
whole, it is more accurate to apply the 50th percentile risk (1 x 
10-\6\) than the 95th percentile risk, which actually 
overestimates the predicted number of cancer cases for this population 
group. The estimate of

[[Page 61090]]

annual cancer cases within a population is the total number of excess 
lifetime cancer cases divided by a 70-year lifetime.
    EPA used this procedure to derive the results of the revised risk 
assessment. Specifically, in the exposure assessment EPA estimated the 
HEI's dose of each 29 dioxin-like congeners detected in sewage sludge. 
The dose of each congener was converted to a TEQ dose by multiplying 
the congener's dose by the congener's toxicity equivalency factor 
(TEF). The TEQ doses for each of the 29 congeners were then summed to 
yield an overall TEQ dose to the individual for each exposure pathway 
(e.g., inhalation, ingestion). Finally, the TEQ dose was multiplied by 
the cancer slope factor (Q1*) to estimate the excess lifetime cancer 
risk to the individual for each pathway of exposure. EPA estimated 
total lifetime average daily dioxins exposure and excess lifetime risk 
to the HEI by summing lifetime average daily dioxins exposures and 
excess lifetime cancer risks across all of the exposure pathways 
relevant to each modeled individual (adult, child, infant).
    Many commenters questioned EPA's use of the 1985 guidance Q1* 
rather than the slope factor presented for TCDD in the September 2000 
Draft Dioxin Reassessment (USEPA, 2000). They argued that it made no 
sense to assess cancer risk based on the 1985 cancer slope factor when 
EPA itself had developed an alternate value. Another commenter said 
that given the uncertainties in the assessment of the carcinogenicity 
of dioxin and dioxin-like compounds, quantifying a cancer slope factor 
and adopting a linear extrapolation model only magnified the 
uncertainty. EPA conducted its risk assessment utilizing the cancer 
slope factor from the 1985 guidance. Because of the terms of the 
Consent Decree, in the NODA we also evaluated the cancer risks to the 
modeled population by considering the cancer slope factor for dioxins 
in the Draft Dioxin Reassessment (USEPA, 2000). EPA's final decision 
not to regulate dioxins in land applied sewage sludge is in harmony 
with either cancer slope. One commenter believed EPA's existing slope 
factor was outdated and that the ongoing dioxin reassessment, or 
perhaps the Great Lakes Initiative (GLI) cancer slope factor (USEPA, 
1995) reflected more current science.
    EPA believes that use of the 1985 guidance Q1* is reasonable. While 
alternative cancer slope factor calculations have been under review, 
there remains sufficient uncertainty as to whether a different Q1* 
should be used for assessing cancer risk from dioxins exposure and what 
the new Q1* should be. EPA reevaluated the 1985 cancer slope in 1990 in 
the GLI (USEPA, 1995), by examining the pathological data from the 
study upon which the cancer slope factor was derived. From this 
reevaluation, both new tumor incidences and a new scaling factor were 
employed to produce a new cancer slope factor. The GLI cancer slope is 
approximately one half the value of the 1985 cancer slope factor. The 
GLI cancer slope factor was used to establish water quality standards 
for those water bodies. The Agency never officially adopted the GLI 
cancer slope factor in its risk assessments for other programs because 
by 1995 the Dioxin Reassessment was underway and additional science on 
the carcinogenic mechanism for 2,3,7,8-TCDD was evolving. In addition, 
the difference between the cancer risk estimate using the 1985 guidance 
Q1* and other proposals (e.g., the GLI, alternate Q1* used in the NODA) 
would not lead EPA to reach a different conclusion with respect to 
whether the predicted adverse health effects (cancer) from dioxins in 
land-applied sewage sludge requires EPA to regulate dioxins in land-
applied sewage sludge. A more detailed discussion of the cancer slope 
factor is provided in section VII (``Discussion of Scientific 
Information Presented in the NODA'').
    4. Method of Calculating Risk to the Modeled HEI Population: As 
explained previously, using the results of all samples from the EPA 
2001 dioxin update survey, EPA modeled all 29 dioxin and dioxin-like 
congeners individually, and then summed the results for all congeners 
to arrive at the risk for dioxins expressed as TEQ. EPA estimated 
excess lifetime cancer risks and corresponding average lifetime daily 
exposure to dioxins for a highly exposed farm adult and child (see 
section V.D. for a discussion of the EPA 2001 dioxins update survey).
    As described in the NODA, the revised risk includes an analysis of 
exposures to individuals using 3,000 iterations of the Monte Carlo 
analysis. Individuals were subdivided into two exposure scenarios, 
those whose exposures begin during childhood and those whose exposures 
begin in adulthood. To account for the fact that children's intake 
rates vary with age, the analysis used separate sets of exposure 
parameters for four age cohorts: ages 1-5, ages 6-11, ages 12-19, and 
ages 20-70. To capture the higher intake-rate-to-body weight ratio of 
children, a start age between the ages of 1 and 6 was randomly selected 
for all children for each iteration in the probabilistic analysis.
    Children (defined as between one year and six years of age) are an 
important sensitive population in risk assessment because they may be 
more highly exposed than adults. This age range was selected because 
this represents the highest consumption rate (intake/body weight) for 
most of the exposure pathways evaluated in this risk assessment. 
Compared to adults, children may eat more food and drink more fluids 
per unit of body weight. This higher intake-rate-to-body weight ratio 
can result in a higher average daily dioxins dose per body weight for 
children as compared to adults. The estimated excess lifetime cancer 
risk for individuals whose exposure begins in childhood is less than or 
equal to the estimated excess lifetime cancer risk for adults whose 
exposure begins later in life. The reason for this is that children's 
mobility generally is greater than that of adults. That is, overall, 
the period of time that a child will occupy a given residence is 
shorter than the period of time an adult will occupy a given residence. 
Therefore, individuals whose exposures to dioxins from land-applied 
sewage sludge in home-produced foods begins in childhood are, in 
general, assumed to be exposed for a shorter duration than those whose 
exposure begins in adulthood (USEPA, 2003a).
    Infants are also an important sensitive population considered in 
the revised risk assessment. Infants may be exposed to dioxin-like 
compounds via the ingestion of breast milk. The characterization of 
risks to infants of farmers and home gardeners was considered 
separately from the characterization of risks to older children (i.e., 
aged 1 year or older). While risks to children and adults were 
integrated to assess individuals for whom exposure first occurs during 
childhood but continues into adulthood, the lifetime risks to infants 
were calculated separately from the risks to older children (i.e., ages 
1 year or older) and adults. For infants, exposure during the first 
year of life was averaged over an expected lifetime of seventy years to 
derive a LADD that was then used to calculate risk. The ``lifetime'' 
risk to infants thus should be thought of as the contribution to an 
individual's lifetime risk that is due to ingestion of breast milk from 
a mother exposed to dioxins in home-produced foods derived from land-
applied sewage sludge.
    Table 1 below provides percentiles of the distribution of estimated 
excess lifetime cancer risk to a farm family adult and child who 
consume home-

[[Page 61091]]

produced foods derived from land on which sewage sludge has been 
applied.

           Table 1.--Risks and Daily Exposure for Highly Exposed Individuals for All Exposure Pathways
                                        [Q1*=1.56 x 10-4 (pg TEQ/kg-d-1]
----------------------------------------------------------------------------------------------------------------
                                                              Adult *                        Child **
                                                 ---------------------------------------------------------------
                   Percentile                                          Daily                           Daily
                                                       Risk        exposure,  pg       Risk        exposure,  pg
                                                                     TEQ/kg-d                        TEQ/kg-d
----------------------------------------------------------------------------------------------------------------
50th............................................        1 x 10-6          0.0086        1 x 10-6          0.0094
75th............................................        4 x 10-6          0.026         3 x 10-6          0.021
90th............................................        1 x 10-5          0.064         7 x 10-6          0.042
95th............................................        2 x 10-5          0.11          1 x 10-5          0.062
----------------------------------------------------------------------------------------------------------------
* Initial exposure begins in adulthood.
* Initial exposure begins during childhood.

    As Table 1 shows, the median exposed HEI (at the 50th exposure 
percentile), even with the conservative assumptions built into the 
definition of the HEI, has a one in a million excess lifetime risk of 
cancer. An HEI at the high end of the exposure distribution (i.e., one 
at the upper 5 percent exposed or the 95th percentile) has a 2 in 
100,000 excess lifetime cancer risk from exposure to dioxins in land-
applied sewage sludge. Both the lifetime and annual excess cases of 
cancer are considered conservative based on the assumptions used to 
model the HEI. EPA's reference to the 95th percentile exposure scenario 
and risk estimate is accompanied by the understanding that only five 
percent of the total number of individuals modeled in the HEI 
population (estimated to be 80 to 560 individuals nationwide) has an 
estimated lifetime cancer risk of 2 in 100,000 or greater. This risk 
estimate is considered to be unlikely based on the conservative 
assumptions used in constructing the HEI in a farm family. The 
remainder of the modeled HEI population will have a lower potential 
cancer risk because they are less exposed to dioxins than at the 95th 
percentile exposure scenario.
    Certain commenters expressed concern that the 1999 human health 
risk assessment was limited to characterization of cancer risks, 
stating that the non-cancer health effects of dioxins may be a more 
serious concern than cancer because non-cancer health effects may occur 
at lower doses and may affect more body systems. Commenters recommended 
that non-cancer endpoints be considered in Round 2 or that draft 
reference doses be used to evaluate non-cancer endpoints.
    EPA based the revised risk assessment for dioxin-like constituents 
in sewage sludge applied to agricultural land and its decision not to 
regulate dioxins in land-applied sewage sludge on the cancer endpoint 
because it is the most scientifically well-established and well-
supported endpoint. Although EPA and others have been studying non-
cancer human health effects from exposure to dioxins, a methodology to 
adequately assess those risks has not yet been established. Details of 
this assessment and developments in the study of assessing non-cancer 
risks are discussed further in section VII. Discussion of Scientific 
Information Presented in the NODA.

C. Findings Concerning Ecological Effects

    In response to public and peer review comments received on the 1999 
proposal, EPA performed a screening ecological risk analysis (SERA) 
(USEPA, 2003a). The SERA used a two-phased approach that includes: (1) 
an initial screening assessment to determine whether the dioxins 
concentrations in land-applied sewage sludge warranted further 
assessment. This effort was an initial bounding estimate to assess the 
upper bound potential for ecological effects at the high end of 
exposure, and (2) a more refined assessment using a combination of 
higher end central tendency exposure assumptions regarding 
environmental media concentrations, receptor-specific dietary 
preferences, and ecological benchmarks. EPA used a hazard quotient (HQ) 
approach to assess the potential for adverse ecological effects. For 
the SERA, the HQ was the ratio of the modeled exposure and an exposure 
(an ecological benchmark) that is expected to be without adverse 
ecological effects. When HQs are greater than one, exposures exceed 
ecological benchmarks, suggesting the potential exists for adverse 
ecological effects. When HQs are less than one, exposures are less than 
ecological benchmarks, suggesting that there is minimal potential for 
adverse ecological effects. In the SERA, EPA determined that all HQs 
were less than one.
    In the NODA, EPA discussed the SERA and requested comments on the 
methodology, the data used, and the results derived from the SERA. As 
with the revised cancer risk assessment, the SERA used the 
concentrations of dioxins obtained from new sampling data in the 2001 
Dioxin Update (USEPA, 2002b) of the National Sewage Sludge Survey 
(NSSS). As explained in section V.D., the 2001 dioxin update survey 
data consist of sewage sludge samples obtained from 94 municipal 
wastewater treatment facilities, and are considered a nationally 
representative sample.
    The SERA addresses risks to mammals and birds, the receptors that 
are expected to have the highest exposure to dioxins. The assessment 
does not address risks to other receptor groups such as invertebrates 
and plants. The potential for dioxins to bioaccumulate in wildlife 
receptors is specifically addressed through analysis of the ingestion 
pathway. The analysis includes receptors exposed through ingestion of 
both aquatic and terrestrial food items and thus addresses the 
potential for bioaccumulation of dioxins from soil, surface water, and 
sediment.
    The bioaccumulation factors (BAFs) for terrestrial invertebrates 
used in the analysis were derived from empirical data and assume a 
linear relationship between the concentrations of dioxins in soil and 
in food items. However, the BAFs are relatively conservative, and EPA 
considers them adequate for a screening level analysis.
    There was disagreement among commenters concerning the adequacy of 
the SERA and whether dioxins in land-applied sewage sludge posed a risk 
to wildlife. Some commenters agreed with EPA's conclusion that there 
was no serious ecological risk, while others said that the uncertainty 
in the model's applications, and the many ``average''

[[Page 61092]]

values in the assessment, made the low HQs questionable. Other 
commenters indicated there was a potential for bioaccumulation in 
several forms of wildlife.
    EPA believes the SERA is adequate to predict hazards to wildlife 
species from dioxins in land-applied sewage sludge. The SERA was 
designed to be consistent with EPA's Guidelines for Ecological Risk 
Assessment (USEPA, 1998). See the Technical Background Document (TBD) 
for a discussion of the SERA (USEPA, 2003a). Because the ecological 
analysis was a screening analysis intended only to indicate the 
potential for adverse ecological effects, EPA considers the qualitative 
uncertainty analysis to be adequate. The uncertainty discussion 
identifies sources of uncertainty, discusses their implications for the 
outcome of the analysis, and, where possible, indicates whether the 
uncertainty is likely to cause an over or underestimation of risk. 
Screening-level ecological risk assessments are designed to provide, 
for those chemicals and receptors that pass the screen (as in dioxins), 
a high level of confidence that there is a low probability of adverse 
effects to ecological receptors.
    The SERA provides insight into the potential for ecological effects 
from dioxins in land-applied sewage sludge. The approach used shows 
that the exposures to animals in terrestrial and water body margin 
habitats do not exceed protective ecological benchmarks (that is HQs do 
not exceed one), suggesting that dioxins in land-applied sewage sludge 
do not pose a high potential for adverse ecological effects.

D. Indications From the 2001 Survey of Dioxins in Sewage Sludge

    In response to comments on the proposal that EPA needed data more 
current than the 1988 National Sewage Sludge Survey (NSSS) data, EPA 
conducted a national sampling and analysis effort to measure dioxins in 
sewage sludge in 2001 (USEPA, 2002b). The EPA 2001 Dioxin Update of the 
NSSS provides data that support the calculation of unbiased national 
estimates (i.e., based on a stratified random selection of publicly 
owned treatment works) for dioxin and dioxin-like compounds in sewage 
sludge. In addition to being more recent, the 2001 data also include 
concentrations of coplanar PCB congeners, along with dioxin and furan 
congeners. Coplanar PCB congeners were not analyzed in the 1988 NSSS.
    EPA sampled sewage sludge from a stratified random sample of 94 
POTWs selected from the sample of 174 POTWs surveyed in the 1988 NSSS, 
stratified into four size categories: those with a daily flow of less 
than one million gallons per day (MGD), 1-10 MGD, 10-100 MGD, and 
greater than 100 MGD. The 174 POTWs selected in 1988 had been selected 
from the approximately 11,000 POTWs in existence at that time that had 
secondary treatment. The 11,000 were sampled according to stratified 
probability design (i.e., by size based on wastewater design flow). The 
sample for the 2001 Dioxin Update to the National Sewage Sludge Survey 
was a subset of the sample for the 1988 NSSS and thus resulted in a 
statistically valid national estimate of dioxin congener concentrations 
in the Nation's sewage sludge. EPA considers dioxin and dioxin-like 
congener concentrations used in the revised risk assessment to be 
representative of dioxins congener concentrations in sewage sludge 
nationwide because of the sample design. See Section III, Statistical 
Support Document for the Development of Round 2 Biosolids Use or 
Disposal Regulations (USEPA 2002b).
    The sewage sludge samples were processed to produce a single 
representative sample for each facility. In addition, the data reflect 
probability-based survey weights based on the numbers of POTWs in the 
four strata defined on the basis of quantity of flow. Since the few 
POTWs in the flow group receiving more than 100 MGD of influent 
wastewater produce the largest amounts of sewage sludge, the 
probability-based sample design incorporated an over-sampling of large 
POTWs. The survey weights reflect this feature.
    The 2001 dioxins update survey was designed based on the 1988 NSSS 
in order to allow comparability of statistically valid national 
estimates, although, as explained later, a number of factors limit the 
degree of comparison that is possible. A comparison of results for 
dioxin and furan congeners obtained in the 1988 and 2001 surveys is 
presented in Table 2. This table summarizes the results using 
alternative methods for handling non-detect measurements. These 
comparisons do not include coplanar PCB congeners because the 1988 NSSS 
did not collect coplanar PCB congener data.

  Table 2.--National Estimates (nanograms/kilogram dry matter basis) for Dioxin and Furan Congeners in the EPA 2001 Dioxin Update Survey and 1988 NSSS
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Zero for nondetects           \1/2\ minimum level of             ML for nondetects
                                                         --------------------------------      quantitation (ML) for     -------------------------------
        Method for handling nondetects (estimate)                                                   nondetects
                                                               2001            1988      --------------------------------      2001            1988
                                                                                               2001            1988
--------------------------------------------------------------------------------------------------------------------------------------------------------
Mean....................................................           21.70           46.50           21.70           67.30           21.80           88.20
Std. dev................................................           47.5           153.0            47.5           153.0            47.5           157.00
Maximum.................................................          682.00         1870.00          682.00         1870.00          682.00         1870.00
99th%...................................................          100.00          450.00          100.00          453.00          100.00          466.00
98th%...................................................           54.40          402.00           54.40          404.00           54.40          455.00
95th%...................................................           33.30          301.00           33.30          303.00           33.30          340.00
90th%...................................................           31.40           56.70           31.60          152.00           31.70          226.00
50th%...................................................           15.50            5.68           15.50           34.20           15.50           52.40
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The EPA 2001 dioxin survey suggests that dioxins levels in sewage 
sludge have decreased from 1988 to 2001. In addition, the upper 
percentile values obtained in the EPA 2001 dioxins update survey are 
lower than those obtained in the 1988 NSSS. See Statistical Support 
Document for the Development of Round 2 Biosolids Use or Disposal 
Regulations (USEPA, 2002b) for a full discussion of the 2001 updated 
dioxins survey.
    It is not possible to draw firm conclusions with regard to changes 
in dioxin concentrations in sewage sludge nationally, due to 
differences in the two surveys caused by changed circumstances since 
1988 (13 years between surveys). During this time, changes may have 
occurred at POTWs, and there have been changes and improvements in 
analytical methods. Nevertheless, as discussed in the NODA, EPA has 
made a number of

[[Page 61093]]

observations regarding changes in dioxins concentrations in sewage 
sludge based on a comparison of the data in the two surveys. As 
mentioned previously, the 94 POTWs participating in the EPA 2001 dioxin 
update survey also participated in the original 1988 NSSS. Samples from 
14 of the POTWs showed dioxins concentrations (dioxins and furans only) 
equal to or greater than 93 ppt TEQ from at least one of the surveys. 
These same 14 POTWs exhibited the greatest differences in the dioxins 
and furans concentrations when comparing the results of the 1988 and 
2001 EPA surveys. The other 80 POTWs participating in both surveys have 
substantially smaller differences, as well as lower dioxins levels 
measured in both surveys. Of the 14 POTWs with the greatest differences 
between the two surveys, four had large increases in sewage sludge 
dioxins concentrations and ten had large decreases in sewage sludge 
dioxins concentrations from 1988 to 2001.
    No sampled POTW with high levels of dioxins in sewage sludge in the 
1988 NSSS showed high levels in the 2001 update survey. Based on these 
data, EPA infers that POTWs with higher concentrations of dioxins in 
their sewage sludge may experience a greater variability in dioxins 
concentrations over time, and that higher dioxins levels may not remain 
high for a significant period of time. It is possible that POTWs with 
higher concentrations of dioxins in their sewage sludge intermittently 
receive dioxins from unidentified but specific sources via the sewer 
system. Likewise, POTWs with moderate or low levels of dioxins in their 
sewage sludge may experience much less variability in dioxins 
concentrations over time. This second group of POTWs appears to be 
experiencing typical environmental background variation of dioxins 
levels.
    EPA requested comments on the significance of the differences in 
dioxins concentrations in sewage sludge measured in the EPA 2001 dioxin 
update survey compared to dioxins concentrations in sewage sludge 
measured in the 1988 NSSS. Several commenters noted that dioxin levels 
had decreased between the 1988 survey and the 2001 survey. One 
commenter was unsure of the implications of the finding, because 
analytical methods have improved and PCBs were not analyzed in earlier 
surveys, but felt that both dioxin and PCB levels have most likely 
declined because of changes in their use.
    Three commenters said that the results indicated that attendant 
risks were also decreasing; one went on to say that EPA should use the 
findings to promote public confidence in land application of sewage 
sludge and dioxins regulatory limits. Another respondent said that the 
decrease made stringent regulatory requirements for sewage sludge 
unnecessary and that existing dioxins controls are having a noticeable 
effect on environmental releases. One commenter said that the findings 
should give regulatory agencies and the public confidence that 
decisions based on current data sets will provide adequate protection 
under reasonably anticipated future conditions.
    One commenter endorsed EPA's response to previous public comments 
by obtaining new data in the 2001 dioxins update survey to the 1988 
NSSS, saying that the initiative demonstrated EPA's commitment to use 
reliable data to provide accurate risk assessments of sewage sludge. 
Another commenter felt that EPA had inappropriately weighted data from 
the NSSS by giving greater weight to samples from small-production 
POTWs and thereby understating risk estimates. Another commenter was 
unsure whether the study was designed to test the hypothesis that there 
might be differences in dioxins concentrations between small and large 
facilities. Finally, some commenters felt that the survey data support 
taking no action for dioxins in land-applied sewage sludge.
    EPA believes that appropriate consideration of data from small 
POTWs was made in the design of the sample for the survey. A simple 
random sample of POTWs, without regard to the amount of influent 
wastewater, would not have provided adequate representation of the 
POTWs receiving the larger amounts of influent wastewater. In fact, a 
simple random sample, drawn without regard to size, would have been 
dominated by POTWs in the less than 1 million gallons per day (MGD) 
flow group.
    Regarding indications from the data, EPA believes that the data 
suggest an overall decrease in dioxins. New or revised pretreatment 
requirements and pollution prevention measures adopted since 1988 would 
be expected to have reduced dioxins in the influent to POTWs. The 
decrease of dioxins in sewage sludge observed in the two surveys 
supports the Agency's conclusion that new regulatory requirements for 
dioxins in land-applied sewage sludge are unnecessary.

VI. Environmental Justice

    Environmental justice and equity concerns involve consideration of 
the potential for minorities and people of lower economic status to be 
impacted by dioxins exposures to a greater degree than the rest of the 
general population. EPA believes the HEI analysis addresses reasonable 
high end exposures that could represent a subsistence low income farm 
family. The HEI analysis addresses exposure regardless of minority or 
economic status.

VII. Discussion of Scientific Information Presented in the NODA

    For the past 12 years, EPA has been conducting a reassessment of 
the human health risks associated with dioxin and dioxin-like 
compounds. This reassessment is not a final document. In this decision 
the Agency continued its practice of using the best available data 
published from a variety of sources that meet the Information Quality 
Guidelines. The Agency considered all such data and associated 
uncertainty to determine the strength of the evidence in finalizing 
this regulatory action related to dioxin and dioxin-like compounds.

A. Assessing Cancer Risk

1. Incremental Cancer Risk
    As explained in section V.A. of this Notice, the revised risk 
assessment for dioxins in land-applied sewage sludge supporting today's 
final action uses the 1985 Q1* of 1.56 x 10-4 (pg TEQ/kg-
d)-1. The estimated upper bound lifetime risks for highly 
exposed farm family adults using this Q1* range from 2 x 
10-5 at the 95th percentile exposure to 1 x 10-6 
at the 50th percentile exposure for multi-pathway exposure to dioxins 
through land-applied sewage sludge (see Table 1). There are two 
exposure scenarios for adults living in the farm family exposed to 
dioxins in land-applied sewage sludge: (1) Individuals whose exposure 
begins in adulthood referred to as ``Adult'' in Table 1, and (2) 
individuals whose exposure begins in childhood referred to as ``Child'' 
in Table 1. As explained in section V.A., the estimated lifetime cancer 
risks for the child are less than or equal to the estimated lifetime 
cancer risks for the adult. These risks correspond to estimated daily 
exposures for the latter group of adults ranging from 0.11 at the 95th 
exposure percentile to 0.0086 pg TEQ/kg-d at the 50th exposure 
percentile.
    Use of the alternative Q1* of 1 x 10-3 (pg TEQ/kg-
d)-1 that was considered in the NODA would result in 
estimated high-end multi-pathway excess lifetime cancer risks for the 
latter group of adults in the highly exposed farm family ranging from 1 
x 10-4 at the 95th exposure percentile to 6 x 
10-6 at the 50th exposure percentile. These estimated risks 
in the NODA are based on the same daily exposures indicated

[[Page 61094]]

in Table 1. Again, the estimated excess lifetime cancer risks expressed 
for individuals born on the farm (see discussion above and in USEPA, 
2003b) would be less than or equal to the estimated risks for 
individuals exposed to dioxins on the farm starting some years after 
birth (i.e., the corresponding values are 6 x 10-5 at the 
95th exposure percentile and 6 x 10-6 at the 50th exposure 
percentile).
2. Background Cancer Risk
    The significance of the exposure and cancer risk due to a specific 
source such as dioxins in land-applied sewage sludge can be understood 
in the context of general population background exposure to dioxins 
from all sources. In other words, the exposure attributed to a 
particular source can be considered in the context of its contribution 
to the overall risk.
    The background lifetime cancer risk to the general population from 
exposure to dioxins (all sources) is approximately 2 x 10-4 
using the 1985 Q1* of 1.56 x 10-4 (pg TEQ/kg-
d)-1. The background risk to the HEI is identical to the 
background risk to the general population, since it is the risk 
associated with exposure to dioxins from all sources.
    As previously explained, the estimated cancer risk for the HEI from 
exposure to dioxins in land-applied sewage sludge is 2 x 
10-5 using the 1985 Q1*. However, excess lifetime cancer 
risk associated with dioxins in land-applied sewage sludge is very low 
compared to the background lifetime cancer risk from dioxins. At the 
95th percentile, the increase in risk of the HEI (farm family estimated 
to be no more than 11,200 persons in the US) is about 10 percent of 
their background risk. As previously explained, excess cancer cases for 
this modeled population from exposure to dioxins in land-applied sewage 
sludge are estimated to be 0.002 to 0.01, again depending on the HEI 
analysis chosen (USEPA, 2003b), using the 1985 Q1*. Further, EPA 
estimates that the excess lifetime cancer risk to the overall U.S. 
general population from exposure to dioxins in land-applied sewage 
sludge is likely to be much lower than the excess lifetime cancer risk 
to the HEI, and as such, correspondingly lower relative to the general 
population's background risk from dioxins. This is because the general 
population's exposure to dioxins from dietary items grown on farms that 
use sewage sludge as a fertilizer or soil conditioner is significantly 
lower than the modeled HEI farm family's exposure to dioxins from the 
crops that they consume from their farms that use sewage sludge. 
(USEPA, 2003b).
    Note that actual risks for individuals are a function of dietary 
habits, as well as a particular individual's susceptibility to develop 
cancer, and may be higher or lower. Thus, high-end incremental excess 
lifetime cancer risk estimates for highly exposed farm families from 
dioxins in land-applied sewage sludge are approximately an order of 
magnitude (i.e., ten times) lower than background risks.
    Based on this evaluation of the range of cancer risks to the 
modeled HEI , EPA believes the projected cancer risks to the HEI from 
dioxins in land-applied sewage sludge are reasonable.

B. Assessing Non-Cancer Risk

    EPA generally uses a reference dose (RfD) for evaluating the 
potential for non-cancer effects for an incremental exposure that 
results from a specific source of contamination. The RfD is an estimate 
of a daily oral exposure to the human population that is unlikely to 
cause an appreciable risk of deleterious non-cancer effects over a 
lifetime. RfDs for particular contaminants are useful health benchmarks 
when background exposures are low or nonexistent.
    As discussed in section VII of the NODA, background exposures for 
dioxin-like compounds have been quantified by EPA as being in the range 
of 1 pg TEQ/kg/d for adults. On a body burden basis, the background 
body burden for dioxin TEQs for adults in the U.S. has been estimated 
to be 5 nanograms toxic equivalence per kilogram body weight (ng TEQ/
kg), on a whole body weight basis (USEPA, 2002a). As the NODA 
suggested, conventional approaches to calculating an RfD for dioxins 
would result in an RfD that is likely to be substantially below current 
background intakes. For this reason, EPA believes that establishment of 
an RfD that is below typical background exposures is uninformative in 
judging the significance of incremental dioxins exposures on human 
health and therefore not useful for subsequent risk management 
decisions for dioxins. Consequently, EPA has not developed an RfD for 
dioxins.

VIII. Public Comments and Other Considerations

    EPA received over 200 comments on the 1999 proposed amendments to 
the Standards for the Use and Disposal of Sewage Sludge and 27 comments 
on the 2002 June 12, 2002 NODA regarding the land application of sewage 
sludge. The majority of the comments were addressed by the NODA or are 
addressed earlier in this Notice. A summary of other major comments is 
presented below, along with a summary of EPA's responses. A complete 
copy of all public comments and EPA's response to comments can be found 
in the Response to Comments Document in the docket (USEPA, 2003c).

A. Definition of ``Dioxins''

    Several comments were received concerning the proposed definition 
of dioxins. Commenters indicated a preference for two separate and 
distinct definitions for ``dioxin'' and ``coplanar PCBs'' (i.e., 
dioxins would mean tetra through octa chlorinated dibenzo-p-dioxin and 
furan congeners; and coplanar PCBs would mean the 12 coplanar PCB 
congeners).
    EPA Response: As previously mentioned, EPA defined ``dioxins'' in 
the proposed rule as 29 specific congeners of PCDDs, PCDFs, and 
coplanar PCBs that have been found in sewage sludge. The proposed 
definition of ``dioxins'' specifies seven 2,3,7,8,-substituted 
congeners of PCDDs, ten 2,3,7,8-substituted congeners of PCDFs, and 
twelve coplanar PCB congeners. EPA had proposed a definition of dioxins 
using TEF values for dibenzo-p-dioxins and furans described in USEPA 
1989 and the WHO 98 TEF scheme for coplanar PCBs. As explained in the 
NODA (67 FR 40556), EPA now uses the WHO 98 system of TEFs to account 
for the overall toxicity of complex mixtures of all 29 congeners. The 
TEF system is accepted worldwide as the most scientifically defensible 
and most easily implemented method to assess these mixtures in risk 
assessments.

B. The Need for Regulating Dioxins in Land-Applied Sewage Sludge

    EPA received a number of comments regarding the need, or lack of 
need, to regulate dioxins in land-applied sewage sludge. There was 
disagreement among the comments premised on dioxins levels in the 
environment and perceived or real risks. Comments in favor of 
regulation (including setting numerical limits) included suggestions 
that: (1) A regulatory program is needed to ensure that dioxins are not 
land-applied, (2) it is illogical not to have a regulatory limit for 
dioxins when EPA regulated various metals in sewage sludge, (3) a risk-
based limit is necessary, (4) sewage sludge is a significant source of 
dioxins and should therefore be regulated, (5) EPA should establish a 
risk-based limit and not a limit based on the 95th percentile 
concentration of dioxins measured in the 2001 dioxins update survey, 
and (6) EPA has traditionally used a one-in-one-million risk as 
acceptable for regulation,

[[Page 61095]]

and that there is no justification for setting less stringent standards 
for sewage sludge.
    Commenters in favor of not regulating dioxins in sewage sludge felt 
that there was no need for numeric limits or other requirements, 
because the overall risks were well within EPA acceptable limits, that 
the data supported no further regulation, and that EPA failed to 
address the issue of whether further reductions in exposure were 
necessary or cost-effective.
    EPA Response: For the reasons discussed elsewhere in this Federal 
Register notice, EPA has decided not to regulate dioxins in sewage 
sludge that is land applied. These decisions are based on the revised 
cancer risk assessment, the SERA, and 2001 Dioxin Update Survey data. 
Weighing risks using the collective body of scientific information, EPA 
has concluded that the increased risks of humans developing cancer from 
exposure to dioxins in land-applied sewage sludge, as well as effects 
to the environment, are reasonable, and that no further regulation is 
warranted. Therefore, neither numeric limitations nor management 
practices for dioxins in land-applied sewage sludge are being imposed.
    Since the general population consumes only a small fraction of 
their diets from products grown on farms with land-applied sewage 
sludge, EPA assumed that a regulatory decision that is protective of 
the highly exposed farm family is also protective of the general 
population. EPA's risk analysis has shown that when dioxins TEQ 
concentrations in sewage sludge are modeled, only five percent of the 
population was at a risk level of 2 x 10-5. EPA believes 
that the actual risk is likely to be lower, due to the many 
conservative assumptions used in constructing the HEI risk 
characterization.
    Regarding comments that there is no justification for setting less 
stringent standards for sewage sludge than one-in-one-million risk, the 
revised risk assessment for dioxins in land-applied sewage sludge 
indicates that an individual in the highly exposed modeled population 
(estimated to be between approximately 1,600 and 11,200 people) has an 
estimated excess lifetime cancer risk ranging from 1 x 10-6 
to 4 x 10-5 (50th to the 99th percentile exposure) for 
exposure by multiple pathways. EPA further notes that the lifetime 
cancer risk ranging from 1 x 10-6 to 4 x 10-5 may 
be overestimates due to the substantial number of conservative 
assumptions used in the revised risk assessment. As a result, the 
Agency does not agree that the risks discussed here warrant further 
regulation.

C. Groundwater Exposure

    Certain commenters stated that EPA did not take into consideration 
the potential exposure to groundwater impacted by dioxins in land-
applied sewage sludge.
    EPA Response: The Agency did not analyze a groundwater 
contamination pathway because dioxins are hydrophobic and they bind 
very tightly to the sewage sludge/soil matrix. Our analysis found that 
transport of dioxins through the soil to groundwater, in the subsurface 
environment, was minimal. Details are provided in the TBD (USEPA, 
2003).

D. Synergistic Effects

    Some public comments indicated that EPA did not consider 
synergistic effects. They asserted, for example, that dioxins can be 
mobilized by solvents and surfactants, which are common in sewage 
sludge. Commenters also asserted that exposure to dioxins may increase 
susceptibility to other carcinogens and that this dimension should be 
analyzed.
    EPA Response: There are no models or data available to address 
synergistic effects with respect to the fate and transport of diverse 
types of pollutants. Therefore, EPA could not assess such effects from 
other pollutants acting in combination with the 29 dioxin, 
dibenzofuran, and coplanar PCB congeners modeled by EPA. While such 
effects are always possible, EPA is not aware of scientific evidence to 
date suggesting that any such effects are likely to be significant for 
dioxins interacting with other pollutants in sewage sludge. The TEF/TEQ 
approach as outlined in today's notice allows EPA to assess the toxic 
effects from exposure to the sum of all 29 dioxin and dioxin-like 
congeners.

E. Voluntary Program

    EPA received a wide variety of comments on methodologies to reduce 
dioxins sources and contamination. Two commenters agreed with EPA's 
suggested methodology for identifying dioxins sources (i.e., 
identifying dioxins sources by tracing their congener 
``fingerprints''). Some supported the use of voluntary programs in 
combination with regulatory standards and monitoring programs. Others 
suggested that a voluntary program only is sufficient, but that EPA 
should develop guidance to provide additional details and explain how 
communities can utilize the voluntary methodology. There was concern 
about who would define ``high'' concentrations of dioxins in sewage 
sludge or ensure that adequate steps would be taken to reduce high 
dioxins concentrations if such a program were voluntary. Some 
commenters asserted that EPA should positively encourage facilities 
with a history or likelihood of elevated dioxins levels in sewage 
sludge to monitor and investigate possible sources contributing to high 
dioxins levels. One commenter noted that the suggested EPA methods 
would be expensive and perhaps beyond the means of POTWs.
    Another commenter said that EPA should require management practices 
to lessen human exposure to sewage sludge in which dioxins are below 
the numeric limit and should require POTWs to develop pretreatment 
programs to reduce dioxins in sewage sludge and minimize dioxins 
discharges into sewer systems.
    EPA Response: With today's final notice EPA is imposing no 
regulatory requirements on small or large facilities, including 
monitoring. However, EPA believes that there may be local benefits from 
establishing a voluntary monitoring and source investigation and 
identification program for dioxins in land-applied sewage sludge for 
some POTWs.
    EPA believes that voluntary monitoring for dioxins in sewage 
sludge, combined with a source identification program when high 
concentrations of dioxins in sewage sludge are encountered, could 
identify dioxins sources that contribute to any elevated levels of 
dioxins in sewage sludge. Mixtures of the 29 dioxin congeners have 
distinct patterns (i.e., profiles or fingerprints) depending on the 
dioxins source. For example, a congener profile that is dominated by 
chlorinated dibenzofurans is often characteristic of a chemical 
manufacturing source. Voluntary monitoring and source identification, 
and perhaps a follow-up source reduction program, utilizing these 
fingerprints, could assist in the identification and subsequent 
mitigation or elimination of dioxins sources when relatively high 
dioxins concentrations in sewage sludge are detected.
    EPA encourages POTWs to consider implementing a voluntary sewage 
sludge dioxins monitoring and dioxins source identification program 
through an Environmental Management System (EMS) approach. An EMS for a 
wastewater utility that generates sewage sludge is a voluntary program 
that encourages a utility to perform above and beyond mandatory Federal 
and State sewage sludge requirements and, thereby, improve their 
environmental

[[Page 61096]]

performance in all areas of wastewater management including the use or 
disposal of sewage sludge. EMS participants involve citizens in their 
communities to assist in defining improved environmental performance. 
EMS status is awarded to participating utilities only after a rigorous 
review and subsequent certification by a third party. A voluntary 
dioxins monitoring and source investigation program, and suggestions 
for reducing and eliminating sources of dioxins in sewer service areas, 
could help contribute to reducing concentrations of dioxins in the 
community's sewage sludge.
    The biosolids industry most likely will be implementing an EMS 
through the National Biosolids Partnership (NBP). The NBP is a 
partnership formed in 1997 with AMSA (Association of Metropolitan 
Sewerage Agencies), WEF (Water Environment Federation), and EPA (U.S. 
Environmental Protection Agency). Through partnering with sewage sludge 
producers, sewage sludge service contractors such as sewage sludge land 
application companies, sewage sludge users, regulatory agencies, 
universities, the farming community, and environmental organizations, 
the goal of the NBP is to advance environmentally sound and accepted 
biosolids management practices.
    Through a voluntary EMS, being developed for biosolids by the NBP, 
EPA continues to provide the public with educational information, based 
on the best science, about the recycling and disposal of biosolids. EPA 
strongly supports the ongoing efforts of the NBP to develop the EMS and 
to provide correct and timely information and community-friendly 
practices that could be followed via its new communications system. The 
EMS program supports local authorities to find ways to meet and go 
beyond what is required in State and Federal regulations. About 54 
municipalities are now pilot-testing their biosolids EMS programs based 
upon a blueprint developed by the NBP.
    In 2003, the first two municipal wastewater treatment authorities, 
Orange County (CA) Sanitation District and the Department of Public 
Works from the City of Los Angeles, CA were awarded entry into the EMS 
Program by certification from an independent third party auditor. 
Several additional municipalities will be ready to undergo an 
independent third party audit of the EMS program later this year 
(2003). Municipalities involved in the voluntary EMS program are 
reporting benefits they have achieved. They report that their 
participation in the EMS program has resulted in more efficient 
operation, reduced odors from biosolids, less intrusive transport of 
the sewage sludge to land application sites, better communication, and 
meaningful involvement of the public. The Agency plans to continue 
supporting NBP activities and working with municipalities on expanding 
the use of EMS programs in biosolids management. Two NBP Web site 
addresses that present relevant biosolids information are http://www.biosolids.org and http://biosolids.policy.net/emsguide/manual/goodpractmanual.vtml.

IX. List of References

Lorber, M.N. 2002. Evaluating Non-Cancer Risk from Land Application 
of Sewage Sludge Using an Increment Over Background Approach. 
Memorandum from Matthew Lorber, National Center for Environmental 
Assessment, Office of Research and Development, USEPA, Washington, 
DC to Alan B. Hais, Health and Ecological Criteria Division, Office 
of Science and Technology, Office of Water, USEPA, Washington, DC, 
April 2002.
USEPA, 1985. Health Assessment Document for Polychlorinated Dibenzo-
p-Dioxins. EPA/600/8-84/014F. Final Report. Office of Health and 
Environmental Assessment. Washington, DC. September, 1985.
USEPA, 1990. National Sewage Sludge Survey; Availability of 
Information and Data, and Anticipated Impacts on Proposed 
Regulations; Proposed Rule. Federal Register 55 (218): 47210-47283.
USEPA. 1995. Great Lakes Water Quality Initiative Criteria Documents 
for the Protection of Human Health. Washington, D.C. EPA-820-B-95-
006. Office of Water.
USEPA. 1996. Technical Support Document for the Round Two Sewage 
Sludge Pollutants. EPA-822-R-96-003. Office of Water. Washington, 
DC. August 1996.
USEPA. 1997. Exposure Factors Handbook. National Center for 
Environmental Assessment. Washington, DC. EPA/600/P-95/002F(a-c). 
Vol. I: 208 pp. Vol. II: 336 pp. Vol. III: 340 pp. Also available at 
NTIS (Vol. I PB98-124225, Vol. II PB98-124233, Vol. III PB98-124241, 
The Set PB98-124217). See also http://www.epa.gov/ncea/exposfac.htm.
USEPA. 1998. Guidelines for Ecological Assessment (Final). EPA/630/
R-95/002F. Risk Assessment Forum. Washington, DC.
USEPA. 2000. Exposure and Human Health Reassessment of 2,3,7,8-
Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds. Part III: 
Integrated Summary and Risk Characterization for 2,3,7,8-
Tetrachorodibenzo-p-Dioxin (TCDD) and Related Compounds (SAB Review 
Draft). EPA/600/P-00/001Bg. Prepared by the National Center for 
Environmental Assessment, Office of Research and Development, 
Washington, DC. September 2000. Available online at http://www.epa.gov/ncea.
USEPA. 2002a. Notice of Data Availability, 67 FR 40554, June 12, 
2002.
USEPA. 2002b. Statistical Support Document for the Development of 
Round 2 Biosolids Use or Disposal Regulations, Office of Science and 
Technology, Washington, DC.
USEPA, 2003a. Exposure Analysis for Dioxins, Dibenzofurans, and 
Coplanar Polychlorinated Biphenyls in Sewage Sludge, Technical 
Background Document, The Office of Water, Washington, DC.
USEPA, 2003b. Highly Exposed Population Background Document, Office 
of Water, Office of Science and Technology. Washington, DC.
USEPA, 2003c. Response to Public Comments. Office of Science and 
Technology. Washington, DC.
Van den Berg M, et al. 1998. Toxic Equivalency Factors (TEFs) for 
PCBs, PCDDs, and PCDFs for Humans and Wildlife. Environ. Health 
Perspect. 106(12): 775-792.

    Dated: October 17, 2003.
Marianne Lamont Horinko,
Acting Administrator.
[FR Doc. 03-26923 Filed 10-23-03; 8:45 am]
BILLING CODE 6560-50-P