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Regulations (Preambles to Final Rules) - Table of Contents
• Record Type: Air Contaminants
• Section: 8
• Title: Section 8 - VIII. Summary and Explanation of the Standard

VIII. Summary and Explanation of the Standard

A. Scope and Selection of PELs

On the basis of all evidence, OSHA has concluded that the TLVs published by the ACGIH constitute the best available starting point for determining the substances included in this Rulemaking. Thus, the boundaries of the substances to be considered in this standard were established to include all of the substances included in the 1987-88 ACGIH TLV listing. There was widespread support for OSHA's selection of these substances for regulation which increased the Agency's confidence that the substances selected for this generic rulemaking are both necessary and appropriate. See also the discussion in Section I.D. of the Proposal and IV. D. of this preamble.

NIOSH (Ex. 8-47) additionally recommended as a potential source the Nordic Expert Group for Documentation of Occupational Exposure Limits. NIOSH stated:

No single source should be expected to stand alone as a comprehensive list of candidates for regulation. OSHA should construct its own comprehensive list by drawing information from all available sources (Ex. 8-47, p. 20).

OSHA agrees with NIOSH in general, although it determined that it was necessary to select a single, comprehensive list as the starting point for consideration for regulation.

As described in the Proposal, the Agency used both the NIOSH RELs and ACGIH TLVs as starting points for establishing PEL's, and then carefully reviewed all of the literature, comments and testimony submitted in the course of this rulemaking. After careful review and evaluation of this body of information on any given substance and in conformance with Agency policy and statutory requirements, OSHA then determined the appropriate PEL or PELs for each substance.

U.V. Henderson, Jr., Director of Environmental Affairs for the Texaco Company, endorsed OSHA's choice of regulatory candidates by stating: "No substances are included in the listings which should be excluded from the rulemaking" (Ex. 3-593). In this regard, NIOSH also expressed support for the inclusion of the proposed substances but urged OSHA to take further action "immediately upon completion of this rulemaking...to establish PELs for all substances that are excluded from this rulemaking" and for which NIOSH has made a recommendation to OSHA (Ex. 8-47, p. 19). NIOSH stated that OSHA should initiate "consolidated rulemaking...to adopt all NIOSH RELs pending (the initiation of) chemical-specific Section 6(b) rulemaking..." (Ex. 8-47, p. 17). In the future OSHA will review those RELs for which there are no PELs. Based on that analysis, other priorities and resources, OSHA will determine the need to develop PELs for these substances.

For its discussion of health effects, OSHA grouped substances on the basis of the TLV documentation. The substances were divided into fifteen generic health effects groups. These were: neuropathic effects, narcotic effects, sensory irritants, liver and kidney effects, ocular effects, adverse respiratory effects, cardiovascular effects, systemic effects, no observed effects, physical irritants and other effects, odor and taste effects, analogy, biochemical and metabolic effects, sensitizers, and carcinogenic effects. The OSHA analysis also considered three special categories concerned with: change only to the STEL; change regarding skin designation in the TLV; and situations where the TLV is greater than the existing PEL.

OSHA is establishing these new limits for general industry only at this time. In the future, consideration will be given to applying these limits to construction, maritime and agriculture. To attempt to consider these sectors in this rulemaking would have delayed this important process. See also the discussion in Section IV.F. of this Preamble.

B. Start-Up Schedule

OSHA intends that the effective date of the new exposure limits shall be March 1, 1989, in conformance with provisions set forth in Section 6(b)(4) of the OSH Act.

In addition, OSHA has set forth start-up dates for most of its health standards acknowledging that it takes time for employers to evaluate exposures as well as to purchase, install and make operable equipment to control such exposures.

In the case of this standard, OSHA has considered the need for start-up dates to allow sufficient time to take into account the fact that many employers will have to evaluate and make operable controls for several different chemicals. This will undoubtedly require more time than would be necessary for only one chemical.

OSHA believes that September 1, 1989, is a reasonable time by which to evaluate exposures and come into compliance with any reasonable combination of engineering, work practice and respirator control methods. OSHA standards generally have had a period of approximately this length or shorter to come into compliance with an exposure limit with any reasonable combination of controls. See for example the benzene standard, 29 CFR 1910.1028 (m)(2), 52 FR 34460, 345676 (September 11, 1987) and the formaldehyde standard, 29 CFR 1910.1048 (p)(2)(iv), 52 FR 46168, 46296 (December 4, 1987). OSHA experience has indicated that the six month period following the effective date is appropriate and sufficient to come into compliance with any reasonable combination of controls.

The proposed rule (53 FR 20960 et seq.) suggested six months from the publication date of the final regulation as a reasonable time for employers to evaluate the exposures of their employees and to come into compliance using any combination of respirators, work practices and engineering controls. Several commenters, such as the Texaco Company (Ex. 3-593) and the Synthetic Organic Chemical Manufacturers Association (SOCMA) (Ex. 3-891), indicated that such an approach was appropriate. The Kerr McGee Corporation (Ex. 3-623) was more specific in its comments and contended that the initial 6-month period should be extended to a 24-month period to allow industry sufficient time to monitor and develop the necessary control measures. The American Paper Institute (Ex. 3-685) was also of the opinion that an initial 6-month compliance period would be too short. OSHA believes that the September 1, 1989, date is adequate based on all of the comments received and OSHA's past experience.

OSHA has generally provided a more extended period to come into compliance using the the hierarchy of controls contained in 29 CFR 1910.1000 (e), with its preference for engineering and work practice controls. It takes more time, in general, to plan, purchase equipment, install and make operational engineering controls than to implement other types of control strategies. Examples of representative start-up periods include: 1 to 10 years (depending upon the sector) for the lead standard, 29 CFR 1910.1025 (e); 4 years for the cotton dust standard, 29 CFR 1910.1043 (m); 2 years for the benzene standard, 29 CFR 1910.1028 (m)(2)(ii); and 14 months for the formaldehyde standard, 29 CFR 1910.1048 (p)(2)(v). These dates have varied depending upon OSHA estimates of the difficulties involved. OSHA's experience has been that generally the times for these standards have been sufficient.

In the Proposal, OSHA also estimated that all employers, including those who would have to control exposures for several different chemicals, could achieve compliance within four years using the hierarchy of controls specified in 29 CFR 1910.1000 (e) (i.e., engineering controls, work practices, and if these are not feasible, personal protective equipment). Regarding the four-year engineering controls implementation date schedule, OSHA received a number of comments. Generally industry supported the four-year period. NIOSH (Ex. 8-47) suggested that two years was a reasonable time for compliance, and a number of unions supported that period. The Fibre Box Association, however, recommended ten years (Ex. 3-823).

In testimony July 15, 1988, related to the experience of the Washington State Occupational Safety and Health Administration with respect to updating permissible exposure limits, Stephen M. Cant stated (Ex. 20):

Washington's PELs became effective thirty days after adoption and did not include a lengthy phase-in for engineering controls. No protests, no complaints, and no observable difficulties have been encountered; however, use of good judgment is always critical to successful enforcement. Engineering controls are not always feasible, although significant improvement, if not total control, is often obtained. In practical terms, longer interim times between implementation and full engineering control tends to occur with lowered PELs and in some cases respirators provide the only control or are used in combination with engineering.

OSHA has evaluated the data from various industries regarding the time needed to come into compliance with the hierarchy of controls set forth in 1910.1000 (e), and has determined that it is feasible for employers in nearly all operations to achieve compliance using engineering controls by December 31, 1992. OSHA's experience is that for substances of normal difficulty, one to two years is sufficient. The longer approximately four-year period takes into account that some employers will have to control several substances and also considers those few substances where compliance may take greater efforts for some employers. Because of the large number of employers and types of industry OSHA covers, OSHA does not believe a very short period similar to that used by the State of Washington would be feasible. For a very small number of specific operations (involving 4 substances - carbon monoxide, carbon disulfide, sulfur dioxide and styrene - which are discussed in this preamble in Section VII.), OSHA has indicated that employers may use any combination of controls and that the burden of proof that the final rule's limits can be achieved in these designated operations using engineering controls will rest with the Secretary of Labor, rather than the employer.

Since OSHA is in the process of reviewing regulations relating to the hierarchy of controls, it asked in the Proposal whether the phase-in period should be based on the final decisions in that rulemaking. Most of those who commented supported fixed dates. The Dow Chemical Company (Ex. 3-741) urged the Agency not to wait to set a start-up date for this rule. A few companies (Exs. 3-669 and 3-527) suggested that the Agency delay the coming-into-compliance period until after publication of any new regulations on this subject; these commenters cited costs of compliance as a major concern.

OSHA concludes that fixed compliance dates are, in general, more appropriate. The times set are reasonable. The additional protection for many workers is a very important goal. Only a small number of participants supported the alternate approach. However, OSHA is setting forth the possibility of a one year extension as discussed below.

OSHA did not raise the issue of methods of compliance in this rulemaking. The exposure limits required after the Transitional Period, are to be achieved with the then current hierarchy of controls set forth in 29 CFR 1910.1000 (e).

In a separate Rulemaking OSHA will be requesting public comment on methods of compliance shortly. The results of that review may lead to change or no change in the OSHA hierarchy of controls as set forth in 29 CFR 1910.1000 (e).

As discussed, OSHA has concluded that 4 years is a reasonable period for coming into compliance with the new exposure limit through the methods of compliance set forth in 29 CFR 1910.1000 (e) with its preference for engineering and work practice controls. If however, the rulemaking on methods of compliance has not been completed and published in the Federal Register by December 31, 1991, either with a determination to modify or not to modify, then some added flexibility is appropriate.

Accordingly para. 1910.1000 (f)(2)(ii) provides that if the methods of compliance rulemaking is completed by December 31, 1991, then compliance with paragraph (e) to lower exposures to the new limits is to be achieved by December 31, 1992. If, however, the methods of compliance rulemaking is not completed by December 31, 1991, then compliance with paragraph (e) to the new limits is to be achieved by December 31, 1993.

OSHA proposed that in the Transitional Period, the existing exposure limits are to be achieved with the hierarchy of controls specified in 1910.1000 (e). That has been the requirement since 1971. Participants did not object to this provision. OSHA is maintaining this provision in the final standard. Between September 1, 1989, and December 31, 1992, the existing limits from Tables Z-1 (which have been placed in the Transitional Limits Columns of Table Z-1-A), Z-2, Z-3 are to be achieved by the hierarchy of controls specified in 1910.1000 (e). This is a protective approach and no evidence has been presented to contradict it. Of course the final rule limits are to be achieved by any reasonable combination of controls from Sept. 1, 1989 to Dec. 31, 1992 or Dec. 31, 1993 as explained elsewhere.

C. Analytical Methods

In the proposal, OSHA included an appendix of analytic methods. It requested comments on those methods and on other methods, OSHA identified seven substances for which it was not aware of acceptable analytical methods. OSHA requested comments on how it should handle substances with no analytical method. It suggested that one approach was to issue a new limit but stay enforcement until a new method was developed.

OSHA received few comments on the methods it proposed, alternate methods, or the approach to be followed for those few substances where OSHA was not aware of a practical method. Both NIOSH (Ex. 8-47) and the Los Alamos National Laboratory (Ex. 3-741) expressed concern about promulgating limits for substances without existing or adequate sampling and analytical methods, i.e., substances requiring special attention because of the lack or inadequacy of methods to measure them in airborne concentrations (53 Fr 20978). For the substances identified by OSHA as lacking an available method, Los Alamos representatives stated that rulemaking "should be delayed until adequate and validated procedures are developed" (Ex. 3-1095). NIOSH agreed with OSHA that substances without existing or adequate sampling and analytical methods should receive special attention (Ex. 8-47). According to NIOSH, "it is important that NIOSH and OSHA work together on a method development scheme that will allow the appropriate validated methods to be developed in a prioritized fashion..."; however, NIOSH was not in favor of delaying the implementation date of the final rule because of sampling and analytical deficiencies (Ex. 8-47).

OSHA has reviewed the few comments and the methods identified. OSHA concludes that, for all but the seven substances identified below, there is an adequate sampling and analytic method for enforcement purposes.

For a few of the substances where OSHA believes there are adequate methods, NIOSH points out that there has not been extensive inter-laboratory cross checking. This procedure (which is known by the technical term "validation") does improve analytic techniques but is not necessary for typical enforcement purposes.

Therefore, OSHA finds that it is appropriate to adopt PELs for all of those substances identified in the Appendix of Section XI as having available in-house sampling and analytical methods. Copies of information on these methods have been submitted to the docket for this rulemaking (Ex. 12) and are available to all parties. Industry and union participants have not criticized these techniques.

In the Proposal, OSHA identified seven substances as not having adequate sampling and analytic techniques for enforcement. OSHA subsequently was informed of reasonable techniques for two of these. However, it also determined that two other substances with inadequate sampling methods were not listed in the Proposal. The list of seven substances now includes aluminum alkyls, ethylidene norbornene, hexafluoracetone, mercury [alkyl compounds], oxygen difluoride, phenylphosphine and sulfur pentafluoride.

OSHA believes it is appropriate to adopt PELs but stay enforcement of these PELs until adequate sampling and analytical methods are available. At such time OSHA will publish in the Federal Register its determination that such methods exist (together with a copy of the method), and indicate the proposed effective date for enforcement of the PEL for the substance in question.

OSHA notes the overwhelming success of the private sector and the joint efforts of NIOSH and OSHA to develop sampling and analytical methods in this area in the past. In 1971, at the time of the promulgation of OSHA's original Z-Tables, sampling and analytical methods were available for only a few of the hundreds of substances on these Tables. In the intervening years, NIOSH, OSHA and the private sector have developed and tested hundreds of methods and have made these available to the industrial hygiene community in several volumes of documented methods (OSHA Analytical Methods Manual and NIOSH Manual of Analytical Methods). OSHA is confident that the two agencies and the private sector will work together to develop rapidly methods for these substances.

D. Content of Standard

The present 29 CFR 1910.1000 contains three Tables and 5 paragraphs. The Tables Z-1, Z-2 and Z-3 express exposure limits for approximately 450 substances in various formats. Paragraph (a) states how Table Z-1 is to be complied with, paragraph (b) how Z-2 is to be complied with and paragraph (c) how Table Z-3 is to be complied with.

Paragraph (d) states the rule to be followed if there are exposures to more than one substance covered by the standard. Paragraph (e) states the hierarchy of controls to be followed in achieving the limit.

In OSHA's Proposal, it opened the rulemaking only to the appropriate exposure limits for 260 substances already included in Tables Z-1, Z-2, and Z-3 and 168 substances with no prior exposure limits. OSHA did not open any substantive issues as to Paragraphs 1910.1000 (a) through (e), or as to the approximately 169 substances in Tables Z-1, Z-2, and Z-3 for which OSHA did not propose to consider changes. However, the need for format changes was recognized since there would be the need to integrate conveniently for the public both old and new exposure limits.

OSHA proposed a new Table Z-4 which included all of the 428 substances which OSHA proposed to consider for new exposure limits. A new paragraph (d) was proposed to indicate how Table Z-4 was to be complied with including Time-Weighted Average (TWA), short term exposure limits (STEL), ceiling limits and skin designations. The provisions of proposed paragraph (d) were opened for public comment. The other paragraphs were proposed only for format changes so that the new limits could be incorporated without confusion. The existing paragraph (d) was redesignated paragraph (f).

There were a number of recommendations by the public on how the exposure limits could be formatted so they would be more convenient for the public to use. OSHA has carefully considered how to present the exposure limits in a manner most convenient for the public. The format of this final standard and Tables reflects that effort.

OSHA is deleting Table Z-1 and inserting Table Z-1-A. (The change in nomenclature is designed to avoid confusion between the two Tables). For the convenience of the public, Table Z-1-A includes every substance regulated by OSHA in subpart Z.

Therefore, Table Z-1-A includes all new substances regulated for the first time in this rulemaking, all substances regulated before in Tables Z-1, Z-2, and Z-3 for which OSHA is promulgating new exposure limits and also those substances regulated before in Tables Z-1, Z-2, and Z-3 for which OSHA considered changing exposure limits but concluded that the exposure limit should remain unchanged. All of these exposure limits were substantively considered and were at issue in the rulemaking. They have been issued or reissued as section 6(b) standards.

Secondly, Table Z-1-A includes several groups of substances which were not considered for change or opened for comment in this rulemaking. They have been placed in Table Z-1-A for the convenience of the public and reformatted but no substantive changes have been made. These include 169 substances which had been located in Tables Z-1, Z-2 and Z-3 which OSHA did not propose to consider changes for and which are carried over substantively unchanged.

For some of those substances located before in Tables Z-2 and Z-3, the the format of presentation could not fit into the columns of Table Z-1-A. In that case Table Z-1-A references the fact that those substances' limits appear in Table Z-2 or Z-3.

These substances which were not opened for rulemaking and which appeared before in Tables Z-1, Z-2, or Z-3 can be identified by having identical limits in both the Transitional Limits Columns and the Final Rule Limits Columns of Table Z-1-A. The identical nature of both limits may require examination of a cross reference to Table Z-2 or Z-3. All of these substances were originally issued as Section 6(a) standards.

Also listed in Table Z-1-A are all substances which have individual standards in Sections 1910.1001 through 1910.1048. In those cases the exposure limit is not listed in Table Z-1-A, but there is a cross reference to the section where the complete standard for that substance is located.

There are also three substances (benzene, cotton dust and formaldehyde) which have single substance standards in 1910.1001 through 1910.1048, for which exposure limits in Tables Z-1 or Z-2 were retained for certain sectors, operations or circumstances not covered by the single substance standard. These limits are either presented directly in Table Z-1-A, or are cross referenced to Table Z-2. An explanatory note indicates where these situations apply.

Through these formatting changes, all substances regulated in Subpart Z are listed in alphabetical order in Table Z-1-A. Also included (where possible) is a CAS number to help identify each substance. The CAS number is for information purposes only. Enforcement is based on the substance name. For an entry covering more than one metal compound measured as a metal, the CAS number for the metal is given. This seemed more convenient than stating "varies with compound." However, the limit covers all the compounds specified by the name. This formatting will facilitate the use of these Z Tables.

As discussed above, there will be a transition period. Until September 1, 1989, the existing limits of Tables Z-1, Z-2 and Z-3 continue to apply. These are presented, or cross referenced in the Transitional Limits columns of Table Z-1-A. The methods of compliance hierarchy, as set forth in Sec. 1910.1000 (e) applies to these limits. For substances where there has been no change in limits, the methods of compliance specified in para. 1910.1000 (e) have been applicable to achieve the limit specified since 1971 and will remain applicable without gap into future unless subsequently amended. The September 1, 1989, and December 30, 1992, dates do not effect the methods of compliance or exposure limit for substances whose exposure limits have not been changed. Substances which fit into the unchanged limits category can be recognized because the limits specified in both Transitional Limits columns and Final Rule Limits columns are the same.

Between September 1, 1989, and December 31, 1992, two limits will be applicable for substances which had an OSHA limit and for which OSHA changed the limits in this Rulemaking. The methods of compliance hierarchy set forth in 1910.1000 (e) will apply to the limits noted in the Transitional Limits columns. The additional protection to achieve the more protective limits noted in the Final Rule Limits columns can be achieved using any reasonable control methods as set forth in para. (f)(2)(ii).

An example may assist in explaining this requirement. Chemical A has a limit of 100 ppm in the Transitional Limits columns and 50 ppm in the Final Rule Limits columns. Between September 1, 1989, and December 30, 1992, 100 ppm must be achieved with the hierarchy of controls specified in Para. 1910.1000 (e) with its preference for feasible engineering and work practice controls. During this period, the additional protection from 100 ppm down to 50 ppm must be achieved by any reasonable combination of engineering controls, work practices and personal protective equipment as specified in para. 1910.1000 (f)(2)(i).

After December 30, 1992, the methods of compliance specified in para. 1910.1000 (e) shall apply to the limits specified in the Final Rule Limits column for all substances with changed limits. The limits specified in the Transitional Limits column shall no longer be applicable.

New substances not previously regulated by OSHA have their exposure limits appear only in the Final Rule Limits columns. For those substances, the methods of compliance specified in para. 1910.1000 (f)(2)(i) apply between September 1, 1989, and December 30, 1992, to achieve the airborne exposure limits specified. After December 30, 1992, the methods of compliance specified in para. 1910.1000 (e) apply.

If no final rule has been published in the Federal Register by December 31, 1991, amending or determining not to amend paragraph (e) of this section, then the permissible limits specified in the Final Rule Limits columns of Table Z-1-A shall be achieved by the methods of compliance specified by paragraph (e) of this section effective December 31, 1993, and paragraph (f)(2)(i) of this section shall remain in effect through December 30, 1993.

As discussed above, some substances are listed in the Transitional Limits or Final Rule Limits columns by cross reference to Table Z-2 or Z-3. Those substances are considered to be in the Transitional Limits columns or Final Rule Limits columns just the same as if the exposure limits were presented in those columns. Consequently, the methods of compliance apply the same, whether the exposure limit is listed directly or listed by cross reference to Table Z-2 or Z-3.

The operational language for Table Z-1 is in 29 CFR 1910.1000(a) (1988), for Z-2 is in 1910.1000(b) and Z-3 in 1910.1000(c). The language of each was not identical because they had different historical sources. It is and has always been OSHA's interpretation that the language, though slightly different, had the same meaning.

In this rulemaking the Table Z-1 has been integrated into the Transitional Limits columns of Table Z-1-A. The operational language that had been in 29 CFR 1910.1000(a) (1988) becomes paras. 1910.1000 (a)(1) and (2). Paragraphs 1910.1000 (b) and (c) are carried over. Some word changes are necessary to these paragraphs to integrate Table Z-1-A into the regulatory framework and to cover the transitional period. These are just formal changes and no substantive changes in the regulations are intended by the formal changes in the language of paras. 1910.1000 (a)(1), (a)(2), (b) and (c).

Paragraphs 1910.1000 (a)(3), (a)(4) and (a)(5) are new. Necessary explanation of them is given below.

Paragraph 1910.1000(d) contains the computation formulas when employees are exposed to more than one toxic substance at the same time and 1910.1000(e) is the hierarchy of controls. OSHA did not open the issue of whether substantive changes should be made to these paragraphs in the proposal. A few comments were received recommending substantive changes. OSHA has not considered them in this proceeding. This rulemaking is sufficiently broad so that resources were not available to consider those recommendations and, of course, no notice was given that OSHA was considering changes to these paragraphs. Accordingly there are no substantive changes to these paragraphs and that was not an issue in the rulemaking. No changes at all are made to para. (e). It is reprinted unchanged for the convenience of the public.

OSHA is making only format changes to para. (d). Those are needed to incorporate Table Z-1-A. They also make clear OSHA's existing position that para.(d) applies to all of Subpart Z. See 53 FR 21241. The names of chemicals in the example are changed to A, B, and C since the exposure limits for the named chemicals have been changed. This should prevent confusion. All of para. (d) is reprinted for the convenience of the public. It should be noted that paragraph (d) had been proposed to be redesignated as paragraph (f) in the Proposal. In the final rule that has not been necessary because of the change in format.

In addition, since OSHA is proposing no changes to Part 1917, Marine Terminals, which references the existing Z-1, Z-2 and Z-3 Tables, the limits shown in the Transitional Limits columns of Table Z-1-A or the limits columns of Z-2 and Z-3 will remain in effect for Marine Terminals. (OSHA in a follow-up rulemaking will consider adoption of new limits for the Construction and Maritime Industries).

For some substances, OSHA proposed using the 10-hour TWA given in the NIOSH RELs as a new PEL. It should be noted that NIOSH generally refers in its criteria documents to airborne concentrations of a substance as a "time-weighted average (TWA) exposure for up to a 10-hour work shift in a 40-hour work week." OSHA has concluded that this is equivalent to the OSHA definition of an 8-hour work shift for a 40-hour work week. OSHA received limited comments regarding this question. NIOSH (Ex. 8-47) provided the most detailed response explaining the history of the 10-hour TWA and why the same TWA REL was intended to be applied to 8-hour and 10-hour work days in a 40-hour work week. NIOSH explained that the 10-hour REL originated during the energy crisis of the 1970s, when many employers began to use 10-hour/4-day work schedules to conserve energy (Ex. 8-47, p. 25). Thus, the 40-hour work week rather than the length of a workday is, in NIOSH's view, the important time element in the (concentration) X (time) equation: any given REL can be applied to either four 10-hour days or five 8-hour days without being exceeded. NIOSH supports OSHA's proposal to apply 10-hour NIOSH RELs to 8-hour days by stating:

The action proposed by OSHA in this rulemaking relative to these RELs is consistent with that original intent (Ex. 8-47, p. 26).

In this final rule, OSHA is therefore applying certain values derived from 10-hour NIOSH RELs as 8-hour TWA PELs.

NIOSH REL ceiling values are based on time intervals which range from instantaneous to 120 minutes. OSHA asked in the Proposal whether, for convenience of enforcement fewer time limits could be used. There were a few comments which gave support to this possibility. After consideration of the record, OSHA has concluded that PELs based on REL ceilings of 10, 15 and 20 minutes shall be made 15-minute STEL's in order to achieve greater uniformity and simplicity in the standard. However, OSHA has decided that the 30-minute, 60-minute and 120-minute ceilings, if adopted, shall remain as specified since those times are so different.

The ceiling limits in Table Z-1-A are consistent with the ACGIH definition. If instantaneous measuring devices are available, then the ceiling limit shall not be exceeded in an instantaneous measurement. If instantaneous measuring devices are not available, then the exposure is to be measured over a 15-minute period. Therefore, some of the ceiling limits are equivalent to STELs.

OSHA proposed PELs for some substances where the basis for the proposal also included a carcinogenicity designation (e.g., TLV with an A1 or A2 designation; REL with a Ca designation). OSHA asked in the Proposal whether such chemicals should have a cancer designation included in the table. Some commenters (Exs. 3-741 and 3-891) indicated that OSHA's Hazard Communication Standard already requires employers to inform employees about the carcinogenic hazards of any substances listed as carcinogens by IARC or NTP. According to these respondents, identification of substances as carcinogens in the Z-Tables would therefore be duplicative and could cause confusion (Ex. 3-891). Other commenters (Exc. 3-593, 3-1095, 8-16 and 8-47) favored the addition of a cancer designation to carcinogenic substances included in the Z Tables. For examples, the American Industrial Hygiene Association (AIHA) stated:

AIHA would support the inclusion of a designation on carcinogenicity...provided that such designation reflects the weight of evidence for carcinogenic effects....(Ex. 8-16, p. 14).

NIOSH (Ex. 8-47) concurred in recommending the inclusion of such a designation in the final rule's Z-Tables.

OSHA has carefully reviewed the record evidence on this issue and has investigated the various evaluative criteria used by scientific and regulatory bodies to determine the classification of a substance as a carcinogen. The Agency notes that each organization has a different system and that the criteria used rarely coincide. Thus, the ACGIH uses two designations, A1 and A2, to reflect the strength of the evidence for a substance's carcinogenicity while the EPA has 5 classifications that represent different kinds of evidence. OSHA believes that the inclusion of a cancer designation on the Z-Tables would further complicate this already complex situation by adding yet another classification system to those already in use. OSHA is also concerned that adding cancer designation to the Z-Table limits would require frequent updating and revision as additional substances are identified as carcinogens in the future. Therefore, OSHA has determined not to add a cancer designation to the Tables.

Paragraphs 1910.1000 (a)(3), (a)(4) and (a)(5) are new. Paragraph (a) (3) requires and employer to maintain an employee's exposure below the Time Weighted Average (TWA), Short Term Exposure Limit (STEL) and/or Ceiling specified in the Final Rule Limits Columns of Table Z-1-A. Paragraph (a)(5) defines those limits. The language of these two paragraphs is consistent with OSHA past practices and good industrial hygiene. The record of this rulemaking supports the approach taken to the language. OSHA intends this language to be interpreted consistent with similar language in 1910.1000 (a)(1), (a)(2), (b) and (c).

Paragraph (a) (4) puts limits on skin exposure. It states:

Skin Designation. To prevent or reduce skin absorption, an employee's skin exposure to substances listed in Table Z-1-A with an X in the skin column under the Final Rule Limits column shall be prevented or reduced to the extent necessary under the circumstances through the use of gloves, coveralls, goggles or other appropriate personal protective equipment, engineering controls or work practices.

This reflects both format and substantive changes from the language proposed. This preamble discussion also reflects a substantive change from the discussion in the proposal. The substantive changes are in response to many comments in the record.

The ACGIH gave skin designation to substances which could be absorbed through the skin. The proposal preamble stated that the skin notation was used to indicate both substances absorbed through the skin and those which might cause skin irritation. There was much public comment pointing out that the underlying documentation considered only skin absorption and not skin irritation. It also pointed out that the two concepts should not be confused because a substance that could be absorbed might not irritate, and conversely.

OSHA agrees with these comments and their reasoning. Accordingly a skin designation for the final rule is only given to a substance which may be absorbed through the skin.

The use of skin designation does not indicate that the substance may irritate the skin. Similarly, lack of a skin designation does not mean that the substance will not irritate the skin.

The purpose of having the skin designation is to prevent the same toxic effects that the chemical causes through inhalation. The inhalation limit is based on keeping exposure below the limit which will create a significant risk of material impairment of health. If skin absorption is possible, an employee might be below the inhalation limit; however, the additional body burden through skin absorption may create the material impairment which the limit attempts to reduce.

The revised language permits compliance with personal protective equipment such as gloves, goggles and coveralls, engineering controls or work practices. No specific hierarchy is stated. An employer must take appropriate actions to prevent routine or regular exposures. However, except when there is the reasonable possibility of a severe reaction through absorption, the methods need not be such as to prevent the possibility of slight infrequent exposure. This language reflects comments in the record that preventing the possibility of exposure is not always necessary to prevent material impairment of health.

Many existing substances have a skin designation which is indicated in the Transitional Limits columns. Para. (f)(2)(iii) states that they shall remain in effect until August 31, 1989. The skin designations in the Final Rule Limits columns take effect on September 1, 1989. This is sufficient time for employers to institute control practices.

Para. (f)(3)(iii) states that if any of the revised limits are stayed then the limits existing prior to this final rule remain effective until the stay is lifted. If a revised limit is vacated, then the limit existing prior to this final rule remains effective.

Para. (f)(4) stays the enforcement of PELs for seven substances for which OSHA is not aware of a practical sampling and analytic technique as of November 10, 1988, the close of the record. When a suitable method becomes available OSHA will publish a notice in the Federal Register notifying the public of the method and setting a date ending the stay.

E. State Plan Applicability

The 25 states with their own OSHA-approved occupational safety and health plans must adopt a comparable standard within six months of the publication date of this final standard. These States include: Alaska, Arizona, California, Connecticut, (for State and local government employees only), Hawaii, Indiana, Iowa, Kentucky, Maryland, Michigan, Minnesota, Nevada, New Mexico , New York, (for state and local government employees only), North Carolina, Oregon, Puerto Rico, South Carolina, Tennessee, Utah, Vermont, Virginia, Virgin Islands, Washington, Wyoming. Until such time as a State Standard is promulgated, Federal OSHA will provide interim enforcement assistance, as appropriate.

List of Subjects in 29 CFR Part 1910

Air Contaminants, Occupational Safety and Health, Permissible Exposure Limits, Health, Risk Assessment.

[54 FR 2332, Jan. 19, 1989; 54 FR 28054, July 5, 1989; 54 FR 28154, July 5, 1989]

Regulations (Preambles to Final Rules) - Table of Contents

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