[μg/dL], air lead exposures have to be kept under 50 μg/m3” (NIOSH 1978, p. XII-14). In addition, data from the General Motors plant in Muncie, Indiana, indicate that “if yearly average personal sampler air lead exposure … is kept below 100 μg/m3, yearly average blood leads in over 90% of workers will be under [60 μg/dL]. Similarly, if yearly average personal sampler air leads … are kept under 50 μg/m3, yearly average blood leads will be 40 [μg/dL] or lower for over half of the workers. One of the greatest impacts of reducing lead exposure in air from 200 to 100 μg/m3 is a great increase in the number of workers with blood lead levels 40 [μg/dL] or lower” (NIOSH 1978, p. XII-15).
NIOSH also notes that the relationship between air lead and BLL may not be linear over the whole range of exposures: “Incremental changes in air lead exposure in the range up to 100 μg/m3 produce greater increases in blood lead than do similar increases in the range from 100-200 μg/m3” (NIOSH 1978, p. XII-115).
At the time, the OSHA proposal was for an action level of 50 μg/m3, which NIOSH endorsed in its criteria document “as a future goal to provide greater assurances of safety” (NIOSH 1978, p. XII-19). That air level would keep BLLs at about 40 μg/dL or lower in virtually all workers, protecting against “subclinical” effects of lead. NIOSH also endorsed a “vigorous medical surveillance program” for workers exposed above the action level but below the proposed maximum air lead concentration of 100 μg/m3. NIOSH estimated that “even at the proposed air standard of 100 μg/m3, less than half of the workers will have blood lead levels above 40 [μg/dL]” (NIOSH 1978, p. XII-19).
In 1997, NIOSH published a Federal Register notice (62 Fed. Reg. 55407 ) requesting comments and information relevant to the potential health risks associated with occupational exposure to inorganic lead at or below the OSHA PEL of 50 μg/m3. To date, however, no additional recommendations have been proposed by NIOSH.
American Conference of Governmental Industrial Hygienists Guidelines
ACGIH is a not-for-profit organization with a mission for advancing occupational and environmental health and safety through the development and publication of scientific guidelines and research. The organization manages several scientific committees that consist of volunteers in government agencies, academic institutions, labor unions, and industrial companies. The committees are the Threshold Limit Values for Chemical Substances Committee, which develops TLVs for airborne chemical substances and materials; the Biological Exposure Indices (BEIs®) Committee for biologic indicators of exposure to chemical substances and materials; and the Threshold Limit Values for Physical Agents Committee, which recommends guidelines for physical hazards, such as noise, temperature, and pressure. Each committee recommends exposure guidelines to the ACGIH Board of Directors, which ensures that all organizational procedures and policies have been followed before ratification. The recommendations