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

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.

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

[[Page 1948]]

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

[[Page 1949]]

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

[[Page 1950]]

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]

BILLING CODE 4510-26-P