Probabilistic pharmacokinetic modeling of airborne lead corresponding to toxicologically relevant blood lead levels in workers

Abstract

The Department of Defense (DOD) commissioned the National Research Council (NRC) to assess the potential health effects associated with exposure of DOD personnel to lead (Pb) at firing ranges. In that report, NRC concluded that the current Occupational Safety and Health Administration permissible exposure limit and the blood lead levels (BLLs) on which it was based were not sufficiently protective of worker populations covered under the general industry standard. In support of future selection of an occupational exposure limit, the relationship of airborne Pb levels to BLLs is of interest to the DOD. A subset of the BLLs identified as relevant to the management of health risks of exposed workers was selected as targets for extrapolation to equivalent airborne Pb values. The existing O'Flaherty physiologically based pharmacokinetic model for Pb in humans was modified to facilitate probabilistic predictions of DOD worker population BLLs, including 95th percentile values, based on current worker characteristics. Workplace airborne Pb 8-h time-weighted average concentrations of 1.1, 4.0, 6.8, or 9.8 μg/m3 are anticipated to maintain BLLs below 5, 10, 15, or 20 μg/dl, respectively, in the vast majority of DOD workers exposed to Pb under full-time working lifetime occupational exposure.