Approach to the Rule: OSHA’s reasons for placing primary reliance on an air PEL for compliance and citations rather than on biologic monitoring included these: evaluation of the industrial environment focused on the direct measurement and control of sources of lead exposure whereas biologic monitoring was designed to ascertain problems of individual workers and was an indirect measure, or check, of the control of lead; biologic monitoring was not feasible for compliance and citation purposes; and biologic monitoring alone might not provide adequate protection for workers, because excessive exposure to lead would not result immediately in excessive BLLs.
Permissible Exposure Limit
The lead standard requires employers to ensure that no employee is exposed above the PEL. In 1971, OSHA set the initial PEL for lead at 200 μg/m3 as an 8-hour TWA. The PEL was based on American National Standards Institute consensus standard z37.11-1969. The consensus standard did not provide any justification for its level of 200 μg/m3 (43 Fed. Reg. 52952 ). OSHA also used the ACGIH threshold limit value (TLV®) as a national consensus standard to establish the initial PEL (Public Law 91-596). The 1968 TLV for lead was also 200 μg/m3 (43 Fed. Reg. 52952 ). OSHA was required in the OSHAct to set standards by using national consensus standards within 2 years of the OSHAct’s becoming effective (Public Law 91-596).
In 1973, NIOSH recommended that the PEL be lowered to 150 μg/m3. On October 3, 1975, OSHA proposed a new PEL of 100 μg/m3. After the proposal was made, OSHA requested comments, data, and opinions on the lower PEL. Hearings were held in multiple locations in 1977. In light of the information received during the comment period and the hearings, a new lead standard received final certification on August 8, 1978 (43 Fed. Reg. 52952 ).
The OSHA lead standard set the PEL at 50 μg/m3 as an 8-hour TWA, which was technically feasible for industry. In OSHA’s opinion, a lower air lead concentration of 40 μg/m3 would not offer a substantial benefit compared with 50 μg/m3.
An action level is an air concentration that triggers the initiation of required activities, such as exposure monitoring and medical surveillance. OSHA defined the action level for lead as “employee exposure, without regard to the use of respirators, to an airborne concentration of lead of 30 μg/m3 averaged over an 8-hour period” (29 CFR 1910.1025(b)). Exposure monitoring is performed to determine whether employees are exposed to lead above the action level. Some requirements are instituted when the action level is exceeded (see the section “Medical Monitoring” below).