[Federal Register Volume 61, Number 16 (Wednesday, January 24, 1996)]
[Notices]
[Pages 1947-1950]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-952]



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DEPARTMENT OF LABOR
Occupational Safety and Health Administration


Updating Permissible Exposure Limits (PELS) for Air Contaminants; 
Meeting

AGENCY: The Occupational Safety and Health Administration, Labor.

ACTION: Notice of Public Meeting on Updating Permissible Exposure 
Limits (PELs) for Air Contaminants.

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DATE AND TIME: Thursday, February 22, 1996; 9 a.m. to 5 p.m.

PLACE: Frances Perkins Building, Auditorium, 200 Constitution Ave., NW, 
Washington, DC 20210. Metro, Judiciary Square Station on the Red Line.

PUBLIC PARTICIPATION: The meeting is open to the public. The room 
accommodates approximately 240 persons. Pre-registration requested for 
all participants and required for those planning on making a brief 
presentation. To register, please send the following information by 
mail or fax to Julia Pesak at: US Department of Labor/OSHA, Rm. N 3718, 
200 Constitution Ave., NW., Washington, DC 20210 Fax: (202) 219-7125
    Or, to register by e-mail, send the same information to Lyn 
Penniman at: [email protected]
    Information required to register: Name of participant, Organization 
represented by participant, Topic(s) participant desires to address, 
Approximate time requested for each topic, maximum of 15 minutes total 
for each participant.
    Registration deadline: Received by Monday, February 12, 1996.
    Registration confirmation: OSHA will confirm all registrations 
received by the deadline. OSHA will chair the meeting and allot time to 
cover the agenda and permit differing viewpoints to be aired.

AGENDA FOR PUBLIC MEETING: The first portion of the public meeting will 
include background information on OSHAs past effort and current 
strategy for updating Permissible Exposure Limits (PELs), followed by a 
general discussion of OSHAs method for identifying substances for 
inclusion in the current phase of rulemaking. The second portion will 
cover significance of risk, risk assessment methodology as applied to 
both carcinogenic and noncarcinogenic end points, and feasibility 
analysis methodology.

FOR FURTHER INFORMATION: Call Phyllis Yates or Julia Pesak at (202) 
219-7111. Please note that registrations will not be accepted by 
telephone.

SUPPLEMENTARY INFORMATION:

Background

    When the Occupational Safety and Health Administration was 
established in 1971, the Agency was given two years to adopt existing 
federal and national consensus standards. Among other standards, OSHA 
adopted Threshold Limit Values (TLVs) from the American Conference of 
Governmental Industrial Hygienists (ACGIH), which in turn had become 
federal standards under the Walsh-Healy Act. These limits, in addition 
to exposure limits from the American National Standards Institute 
(ANSI), were codified in the Code of Federal Regulations (CFR) as 
Permissible Exposure Limits (PELs) in Sec. 1910.1000, Subpart Z. 
Subpart Z became known as OSHAs Z-Tables, and were enforced by OSHA to 
protect the health of workers from adverse health effects associated 
with overexposure to air contaminants in general industry. Minor 
differences in regulatory history resulted in slightly different limits 
for the construction and maritime industries.
    In the 1980s, it became widely recognized that many of the limits 
in OSHAs Z-Tables were outdated, and in 1988 OSHA proposed to update 
approximately 420 of its PELs in its air contaminants rulemaking. The 
newer PELs were based on more recent scientific information, and that 
information indicated that all but one of the new PELs needed to be 
more protective of worker health than were the old limits. OSHA 
utilized in part the recommendations made by the ACGIH and the National 
Institute of Occupational Safety and Health (NIOSH) in an effort to 
streamline the process. Following hearings and written comments OSHA 
published its final rule on January 19, 1989 (54 FR 2332), reducing 212 
PELs, setting 164 PELs for previously unregulated substances, and 
raising one PEL. OSHA proposed to expand coverage of that rule to the 
construction and maritime industries on June 12, 1992 (57 FR 26002).
    Legal challenges to the standard by industry and labor groups were 
consolidated and heard in the Eleventh Circuit Court of Appeals. In 
July of 1992 the Court issued its decision (American Federation of 
Labor and Congress of Industrial Organizations v. Occupational Safety 
and Health Administration, 965 F. 2d 962). It stated, in essence, that 
OSHA should perform quantitative analysis of risk for noncancer 
endpoints where possible, that more extensive discussions of the health 
evidence for each substance was needed, and that feasibility analysis 
should be more detailed. Though only some of the substances were 
individually challenged, the entire revised air contaminants standard 
was vacated and remanded back to the Agency. Consequently, the Agency 
was obligated to revert back to enforcing the limits set in the early 
1970s.

Purpose

    Establishing an ongoing mechanism for updating its PELs continues 
to be a high priority for the Agency. OSHA seeks comment on the current 
phase of its plan to establish an ongoing, iterative process for 
updating outmoded Permissible Exposure Limits (PELs). Future phases 
will differ from the current phase and include a mechanism for 
establishing PELs for appropriate new substances (not currently 
regulated) under Sec. 1910.1000, subpart Z. This meeting will be the 
second on the topic of PELs with interested stakeholders since the 
standard was remanded in 1992.
    The Agency intends to publish a proposal to update PELs for a group 
of approximately 20 substances in the late spring of 1996. Subsequent 
to the previous public meeting in July 1995, OSHA has further narrowed 
its likely priority candidates for proposed PEL rulemaking. The 
substances included below represent OSHA's current intentions regarding 
the substances to be included in the air contaminants proposal. The 
actual proposal, when published, may add or drop a small number of 
substances.
    The list of substances currently slated for rulemaking, along with 
the agenda of the meeting (including a brief discussion of risk 
assessment and significance of risk issues of interest to OSHA), are 
provided here for the purpose of focusing and facilitating substantive 
discussion during the public meeting for stakeholders. The purpose of 
this meeting is to discuss those general issues which are germane to 
the current air contaminants rulemaking. It is not OSHA's intent to 
discuss health effects information and other issues relevant only to 
specific substances at this particular meeting. The regulatory process 
will provide ample opportunity for interested parties to submit oral 
and written comments on specific substances.

Current Candidates for Proposed Air Contaminants Rulemaking:

Carbon disulfide
Carbon monoxide
Chloroform
Dimethyl sulfate
Epichlorohydrin
Ethylene dichloride
Glutaraldehyde
n-Hexane
2-Hexanone
Hydrazine
Hydrogen sulfide
Manganese & compounds
Mercury & compounds
Nitrogen dioxide
Perchloroethylene
Sulfur dioxide
Toluene
Toluene diisocyanate
Trimellitic anhydride
Vinyl bromide

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Issue I: Priority-Setting for PEL Chemicals

    OSHA requests comment on its selection of priority substances for 
this first phase of updating PELs. In identifying the priority 
substances, OSHA (with assistance from NIOSH) evaluated the following 
criteria: The inherent toxicity of the substance; the number of workers 
exposed to the substance (and in some cases, the amount of the 
substance produced); uses of the substance and prevailing exposure 
levels; the severity of the resulting adverse health effect(s); the 
availability of information useful in quantitative risk assessment, and 
the quality of those data; and the potential for risk reduction. 
Administrative considerations and professional judgement were also 
factored in to the decision-making process. OSHA feels that this 
approach, a hybrid of quantitative and qualitative elements rather than 
a strictly quantitative formula, was appropriate and rational. The 
criteria used to identify these substances are similar to those used by 
OSHA's Priority Planning Process Committee to identify the Agency's 
priorities for regulatory and other actions.
    Although these priority substances were identified on the basis of 
objective criteria, it should not be concluded that these are the only 
substances in OSHA's Z-Tables that require new PELs, nor that these are 
necessarily the highest-risk substances. It is important for worker 
protection that the Agency propose PELs for noncarcinogens as well as 
carcinogens, and for substances which have health effects that 
adversely impact workers' quality of life without necessarily affecting 
mortality. And, while it is important to establish PELs for these 
particular substances, it is of equal importance to the Agency to begin 
to lay the groundwork for a regular and iterative process for updating 
PELs for air contaminants.

Issue II: Risk Assessment Methodology for Carcinogens

    OSHA has gained much experience in conducting quantitative risk 
assessments for carcinogens from past rulemaking efforts. The 
approaches most often employed by the Agency, which rely on use of the 
multistage model with animal data and relative risk models with human 
data to derive dose-response relationships, are well known in the 
scientific community and have been routinely upheld by reviewing 
courts. The Agency does not expect to depart significantly from its use 
of these approaches to derive revised exposure limits for potential 
carcinogens included in the present rulemaking effort. However, OSHA is 
interested in hearing discussion on certain issues regarding the 
details of dose-response modeling for carcinogens, in particular: (1) 
The appropriateness of relying on maximum likelihood estimates, upper 
confidence limits, or other summary statistics for carcinogenic potency 
such as expected values (for example, see Hattis and Goble 1991) to 
derive exposure limits; (2) approaches that can be taken to address the 
issue of interindividual variation in response among humans; (3) the 
use of various interspecies scaling factors when assessing risks from 
bioassay data; and (4) criteria for evaluating the adequacy of data to 
determine when it is appropriate to use pharmacokinetic analysis as 
part of the risk assessment.

Issue III: Risk Assessment Methodology for Noncarcinogens

    OSHA is currently exploring the use of techniques to quantify risks 
of non-neoplastic health effects associated with occupational exposure 
to hazardous materials. This effort is designed to address the Eleventh 
Circuit Court decision. OSHA believes that, wherever data permit, 
conducting quantitative risk assessments for noncancer health endpoints 
provides the most direct route for establishing new or revised exposure 
limits in a manner consistent with the Court decision.
    A variety of methods for establishing exposure limits based on 
noncancer health endpoints have been used by regulatory agencies and 
scientific bodies. One of the most frequently employed methods involves 
setting exposure limits by applying uncertainty factors to no-observed-
adverse-effect (NOAEL) or lowest-observed-adverse- effect (LOAEL) 
levels reported in human and animal studies. OSHA relied on this 
approach to a large extent in the 1989 Air Contaminants rulemaking. 
Although this approach has been widely used in the past, its chief 
disadvantage is that it provides little or no information on potential 
risk levels that may be associated with varying magnitudes of exposure, 
a limitation that was recognized by the Court.
    One of the newer approaches being evaluated by OSHA to conduct 
noncancer risk assessments is known as the ``benchmark dose'' method, 
originally described by Crump (1984). This method is currently being 
used by the Environmental Protection Agency (EPA) to establish 
Reference Doses (RfDs) based on noncancer health effects, and its 
application has been recently studied and described in detail by EPA's 
Risk Assessment Forum (EPA, 1995). This approach uses formal modeling 
techniques similar to those used in cancer risk assessment to develop 
quantitative dose-response relationships based on either human or 
animal studies. The models are subsequently used to estimate a 
benchmark dose associated with a specified excess risk level that lies 
on or just below the observed range of risks (usually 5 or 10 percent). 
The EPA document discusses two approaches for deriving references doses 
from benchmark doses: one employs a system of uncertainty factors to 
account for individual variation in response, extrapolation from animal 
to humans, and severity of the effect, while the other approach reduces 
the benchmark dose by some adjustment factor representing the desired 
reduction in the magnitude of the risk. Thus, the benchmark dose 
approach differs from those used in cancer risk assessments in that the 
models developed are not used to extrapolate risks at very low dose 
levels. Use of the benchmark dose approach has at least two advantages 
over the traditional NOAEL/LOAEL method: (1) Quantitative dose-response 
information can be obtained, which should facilitate regulatory 
decision making; and (2) the approach provides for greater regulatory 
consistency between substances since decisions can be based on 
comparable starting points, i.e., risk levels of 5 or 10 percent.
    Thus, OSHA believes that the benchmark dose approach shows promise 
as a consistent and defensible method by which the Agency can establish 
reasonable exposure limits based on nonneoplastic health effects. As 
such, OSHA wishes to hear considerable discussion on the experience of 
those who are familiar with or who have used this method to evaluate 
public health risks, and what alternative approaches can be utilized 
that address issues raised by the Court ruling on the Air Contaminants 
standard. In particular, OSHA is interested in hearing discussion on 
how to best implement approaches to derive exposure limits from 
benchmark dose values, and how these methods can be interpreted in 
terms of the significance of the risk and the magnitude of risk 
reduction achieved.

Issue IV: Determination of Significant Risk

    For significant risk determinations for carcinogens, OSHA has 
followed the Supreme Court guidance in the Benzene decision. The Court 
stated: ``It is the Agencys responsibility to determine in the first 
instance what it considers to be 

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a ``significant'' risk. Some risks are plainly acceptable and others 
are plainly unacceptable. If, for example, the odds are one in a 
billion that a person will die from cancer by taking a drink of 
chlorinated water, the risk clearly could not be considered 
significant. On the other hand, if the odds are one in a thousand that 
regular inhalation of gasoline vapors that are 2% benzene will be fatal 
a reasonable person might well consider the risk significant and take 
the appropriate steps to decrease or eliminate it.'' (Industrial Union 
Department, AFL-CIO v. American Petroleum Institute, 448 U.S. 601, 655. 
(1980)). OSHA would welcome comments that would enable it to shed light 
on the acceptability of risk levels within this million-fold range.
    OSHA has had less experience in evaluating significant risk for the 
broad range of other adverse health effects experienced by workers who 
are exposed to hazardous levels of chemical substances. OSHA invites 
discussion on appropriate risk levels for effects such as 
neurotoxicity, reproductive effects, and organ toxicity that may 
represent significant risks, and on appropriate criteria (such as 
severity and reversibility of the effect) that should be considered to 
determine when risks of a given magnitude represent a significant risk.

References

    Crump, K.S. 1984. A new method for determining allowable daily 
intakes. Fund. Appl. Toxicol. 4:854-871
    Environmental Protection Agency. February 1995. The Use of the 
Benchmark Dose Approach in Health Risk Assessment. Publication No. 
EPA/630/R-94/007, Washington, DC.
    Hattis, D. And Goble, R.L. 1991. Expected values for projected 
cancer risks from putative genetically acting agents. Risk Analysis 
11:359-363

    Authority: This document was prepared under the direction of 
Joseph A. Dear, Assistant Secretary of Labor for the Occupational 
Safety and Health, 200 Constitution Ave. NW., Washington, DC 20210.

    Signed at Washington, DC, this 19th day of January, 1996.
Joseph A. Dear,
Assistant Secretary of Labor.
[FR Doc. 96-952 Filed 1-23-96; 8:45 am]
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