Document 82eYBRx78OYNKVy8XkJm5ZDkm

22680 . Federal. Register / Vol. 51, No. 119 /. Friday. June 20,1986 / Rules and Regulations The primary reason for adopting an setting an action level will help to action level is that OSHA believes, alleviate these concerns because based on its experience, that It is requiring periodic employee exposure appropriate to begin some protective measurement to begin at the action level actions prior to exceeding the will provide the employer with an permissible exposure limit to help drive increased degree of confidence that exposure levels downward and to employees are not inadvertently optimize the possibilities that the PEL overexposed on unmeasured days. can be met. Also, in the case of The level that should be designated as asbestos, significant health risks exist the action level was an issue during the from exposures to 0.1 f/cc. rulemaking. OSHA had proposed 0.2 f/ Consequently, supplemental protective cc based on the possibility that 0.5 f/cc measures are clearly warranted, especially when they are feasibly instituted. The 0.1 f/cc action level also is consistent with OSHA's enforcement of the medical surveillance provision of the current asbestos standard, which requires examinations at any level, but which OSHA has interpreted to be 0.1 .f/ cc. Another purpose of the action level is to provide an appropriate cut-off point for many of the required compliance activities under the standard. The standard applies to some employers whose employees are exposed to airborne asbestos levels that are below the permissible exposure limits but which are significantly above ambient levels. Such employers are required to perform initial monitoring to determine the extent of their employees' exposures to asbestos. If, on the basis of the results of the initial determination, exposure is below the action level, the employer, may be excused from monitoring and most other protective measures for that employee, even though it would be feasible to continue them for all exposed employees. The action level concept thus provides an objective test for OSHA and employers to permit the discontinuance of certain activities, such would be the PEL and because of the uncertainty about'the lower limit of reliable measurement. The Asbestos Information Association/North America (A1A/NA) stated that an action level of 0.2 f/cc for monitoring and training is inappropriate based on interday variability and measurement uncertainty for asbestos workplaces [Ex. 328], As discussed in the section on sampling and analysis, N10SH has developed modifications to the existing phase contrast method for asbestos determination. By employing the critical aspects of the method (NIOSH Method 7400) and by adopting other procedures that reduce the analytical variability. OSHA believes, based on the record evidence, that reliable measurement can be made at 0.1 f/cc. It is noted here, however, that even if the employer has controlled exposures to below the action level, paragraph (d)(5) of the final.rule requires reinstitution of exposure monitoring "when there has been a change in the production process, control equipment, personnel or work practices that may result in new or additional exposures to asbestos or when the employer has any reason to suspect that a change may result.in new or additional exposures." as medical surveillance, training and Fiber periodic monitoring when exposures are The current definition for "asbestos low.- fibers" is somewhat circular because it A statistical explanation of the heed begins, ". `Asbestos fibers' means for an action level has been discussed in asbestos fibers___ " OSHA has deleted connection with other OSHA health the word "asbestos" and the amended standards. (See, for example, inorganic definition now begins." Tiber' means a arsenic, 43'FR 19584; vinyl chloride. 39, particulate form of asbestos, tremolite, FR 35890; and acrylonitrile, 43.FR 45782). anthophyliite, or actinolite...." Inbrief, although alfemployee exposure The. current definition specifies only measurements on a given day may be the minimum fiber length [5 below the PEL, it is possible that on micrometers) and does not.specify any . dayB when ho measurements are taken, other dimensions. As methods have an employee's actual exposure may been developed to count these fibers, unknowingly exceed the PEL. As Other criteria, for example, the aspect discussed in detail in the section on ratio (the ratio of length to diameter) technological feasibility, some industry have been used in order to standardize representatives expressed concern that counting methods. When criteria of they may be unable.to assure that leve.ls length, diameter, or aspect ratio differ are less.than the PEL every day and from one method to another, the result stated that measurements showing 0.2 f/ could be widely differing counts on the cc levels on any. given day did not mean same asbestos sample. . that levels on unmeasured days would . In the April proposal. OSHA raised not be higher: OSHA believes that the issue of adding an aspect ratio (a ratio of length to diameter) to the definition. The aspect ratio most commonly used throughout the world is 3 to 1 or greater In 1975, both the American Industrial Hygiene Association and the U.S. Public Health Service were recommending the use of the 3 to.l aspect ratio (40 FR 47858). This convention is currently in use in the NIOSH recommended method #P&CAM 239 (Ex. 84-082), and NIOSH method 7400 (counting rules A) specifies that, only fibers with a length to width ratio equal to or greater than 3 to 1 are to be counted (Ex. 84-444). The NIOSH recommended definition for asbestos (Ex. 117A) and the definition for asbestos fiber recommended by the Building and Construction Trades Dept., also AFL-CIO (Ex. 330) specify an aspect ratio of 3 to 1 or greater. Although the current definition for asbestos fiber does not contain an aspect ratio, OSHA has been using the 3 to 1 or greater aspect ratio in its laboratory determinations. This practice agrees with the recommendation made . by NIOSH in its revised criteria document (H-033B, Ex. 5). The experimental evidence in the record indicates that a number of durable fibers, including asbestos, are carcinogenic (Exs. 84-93, 84-131, 84195). Fibers meeting certain criteria of length and diameter appear-to be closely correlated tp the incidence of sarcomas in experimental animals. Using implantation studies, Stanton andcoworkers (Ex. 84-195) examined the relationship between the carcinogenicity of durable fibers and fiber length and diameter. They demonstrated that in female Osbourne-Mendel rats, the probability of pleural sarcomas correlated beBt with the number of fibers that measured 0.25 micrometer or . less in diameter (and more than 8 micrometers in length). Relatively high correlations were noted with fibers having diameters up to 1.5 micrometers (and length greater than 4 micrometers): Although these investigators were able to demonstrate that fibers of a certain size.were associated with a higher incidence of sarcomas, their work did not show a size threshold for carcinogenicity. In addition, these implantation studies demonstrate the carcinogenicity of fibers that have been implanted in the lung and do not address the likelihood that inhaled fibers will actually reach the alveolar spaces. Bertrand aiid Pezerat (Ex. B4-114) showed that the aspect ratio'was related to. the carcinogenicity of the fiber. They reanalyzed Stanton's early data using other, variables and concluded that GLEASON-000928