Standard Practice for Asbestos Exposure Assessments for Repetitive Maintenance and Installation Tasks
4.1 Work practices, engineering controls, personal protective equipment and other precautions to minimize exposure to airborne asbestos fibers have been extensively documented in regulations, training manuals and other publications. The work described in these publications ranges from large-scale abatement projects to minor disturbances and clean-up. Practices E1368 and E2394 address these issues within the context of their subject matter.
4.2 This practice applies to specific types of asbestos work where the same task is performed by various persons without substantial deviation from a documented procedure and with material containing the same type and similar content of asbestos fiber. The exposure from such operations can be expected to remain fairly consistent as long as these parameters do not vary substantially and the workers have received the required training to perform the task.
4.3 Because of the variability in field conditions under which large-scale work such as asbestos abatement is performed, the opportunity to collect sufficient personal air samples under conditions similar enough to establish statistical confidence can be questioned. For this reason, this practice does not address the collection of such samples and their use for determining exposure data to apply on other projects. Users with such requirements are referred to the applicable regulations for guidance.
4.4 There are many tasks, however, that are of short duration and amenable to testing under controlled conditions for assessing worker exposure. These tasks are performed by equipment installers and other tradesmen in the course of their ordinary duties in what this practice refers to as the current job. The following list of potential tasks where ACMs can be disturbed is by no means inclusive and the feasibility of conducting an Exposure Assessment is the responsibility of the user:
4.4.1 Drilling holes through asbestos floor tile and sheet vinyl flooring,
4.4.2 Removing small pieces of floor tile and sheet vinyl flooring to expose the substrate,
4.4.3 Drilling holes through asbestos-cement roofing, siding, ceiling panels, ducts and pipes,
4.4.4 Drilling and cutting holes in wallboard,
4.4.5 Drilling holes in ceiling tiles,
4.4.6 Removing and replacing ceiling tiles,
4.4.7 Patching roofing materials,
4.4.8 Removing window putty and caulking,
4.4.9 Cleaning asbestos-lined or contaminated ducts,
4.4.10 Removing gaskets and packing,
4.4.11 Removing and installing locksets in fire doors,
4.4.12 Taking bulk samples of suspect ACM,
4.4.13 Removing and patching acoustical ceiling texture and fireproofing, and
4.4.14 Removing and replacing insulation on pipes, tanks, boilers, ducts, etc.
4.5 The Exposure Assessment is based on personal air samples taken over a full or partial shift to determine an 8-h TWA exposure and a short-term Excursion Limit exposure, which requires that two sampling pumps be worn.
4.6 Samples are taken for comparison with criteria determined by the user, including but not limited to the following:
4.6.1 Permissible Exposure Limits (PELs), including the 8-h TWA of 0.1 f/cc and the 30-min EL of 1.0 f/cc, or to establish engineering controls, respiratory and personal protection, and other requirements in accordance with 29 CFR 1926.1101;
Note 1: These OSHA PELs will be used for illustration purposes in this practice.
4.6.2 National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit of 0.1 f/cc;
4.6.3 American Conference of Governmental Industrial Hygienists (ACGIH6) Threshold Limit Value (TLV7) of 0.1 f/cc for respirable fibers;
4.6.4 Employee exposure limits imposed by other governmental jurisdictions;
4.6.5 Employee exposure limits to establish engineering controls, respiratory and personal protection, and other requirements of an employer's policy or the requirements of a specification or procedure that applies to the current job; and
4.6.6 Non-occupational exposure limits for building occupants and other affected persons.
4.7 Compliance with the PELs and other criteria is typically determined by analyzing the air samples using NIOSH Method 7400 for Phase Contrast Microscopy, which reports all fibers meeting the counting criteria and does not distinguish between asbestos and non-asbestos fibers. The Exposure Assessment can be based on analysis using NIOSH Method 7402 for Transmission Electron Microscopy, which identifies asbestos fibers and adjusts the fiber count from a NIOSH Method 7400 analysis.
4.8 An important aspect of an Exposure Assessment is determining a margin of safety between the exposures measured during the test and criteria for respiratory protection, regulatory compliance or other purposes. This practice therefore includes a statistical test (Confidence Factor) for the exposure based on the air sample results from a test as described in Section 7.
4.9 The responsibility for comparing the results of the test performed for the Exposure Assessment is given to the competent person, usually but not necessarily someone in a supervisory capacity, who compares the conditions under which the test was performed to those for the current job to which a worker has been assigned. If the work practices and asbestos-containing materials are sufficiently similar in the judgment of the competent person, and the worker has been trained on the work practice using simulated asbestos-containing materials, the competent person certifies that the Exposure Assessment applies to the current job for purposes of respiratory protection and other precautions. A form is provided in Appendix X1 for this purpose.
Note 2: OSHA regulations in 29 CFR 1926.1101 permit an employer to dispense with respiratory protection and other precautions on the basis of an Exposure Assessment (sometimes called a Negative Exposure Assessment) or on the basis of “objective data.” This practice does not use the terms “Negative Exposure Assessment” and “objective data,” and the responsibility for elimination of protective measures based on an Exposure Assessment remains with the competent person. 29 CFR 1926.1101 requires a “high degree of certainty” that the PELs will not be exceeded, but does not define this parameter.
1.1 This practice establishes procedures for assessing the exposure of workers to airborne fibers who perform repetitive tasks of short duration where small quantities of asbestos-containing materials must be disturbed in order to perform maintenance and installation activities.
1.2 This practice describes the facilities and equipment for performing the tasks under controlled conditions for the express purpose of collecting personal air samples to determine worker exposure. The tasks are performed on actual asbestos-containing materials during Exposure Assessment tests and precautions are taken for personal protection and avoiding contamination of adjacent spaces.
1.3 This practice describes the air sample collection procedures, the analytical methods for the air samples, and the calculation of worker exposure including the use of statistical confidence limits. This practice differentiates between the test to obtain exposure data and the current job to which the data are applied, and describes the duties of the individuals who conduct these separate activities.
1.4 The results are applied to the current job as defined herein for determining worker protection such as respiratory protection or for other purposes as determined by the competent person responsible for the current job. The results of the tests shall not be applied to current jobs that are expected to differ substantially from the test conditions in work practices, material properties or other factors that might affect the concentration of airborne asbestos fibers.
1.5 This practice is not intended to be used for asbestos abatement work for which the objective is the removal of asbestos-containing materials. It is designed to assess exposures for short-term repetitive tasks. Compliance with regulatory requirements as to the purpose of the work and limits on the quantity of asbestos-containing materials disturbed is the responsibility of the user.
1.6 This practice describes procedures for determining exposure to airborne asbestos fibers. It does not purport to determine the risk of acquiring an asbestos-related disease for any individual, trade or work practice, nor does it represent that compliance with any criterion constitutes a “safe” level of exposure that is free of such risk.
1.7 Hazards—Asbestos fibers are acknowledged carcinogens. Breathing asbestos fibers may result in disease of the lungs including asbestosis, lung cancer, and mesothelioma. Precautions should be taken to avoid breathing airborne asbestos particles from materials known or suspected to contain asbestos. See 2.2 for regulatory requirements addressing asbestos.
1.8 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.
1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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