US Environmental Protection Agency (EPA) has also released an external review draft of its Integrated Science Assessment for Lead in support of its review of the National Ambient Air Quality Criteria for lead. The NTP and EPA reviews provide compelling evidence of a variety of health effects associated with BLLs of 10-40 μg/dL and of some health effects at lower levels.
In light of knowledge about the hazards posed by occupational lead exposure, the Department of Defense (DOD) asked the National Research Council to evaluate potential health risks from recurrent lead exposure of firing-range personnel. Specifically, DOD asked the National Research Council to determine whether current exposure standards for lead on DOD firing ranges protect its workers adequately. To address its charge, the committee focused on determining whether there is evidence of adverse health effects in people who have BLLs of 40 μg/dL or lower because that is the implicit level in the OSHA standard to protect workers from adverse health effects; indeed, the standard allows workers to have a BLL up to 40 μg/dL for a 40-year working lifetime. The committee also considered measures of cumulative lead dose. These can include the measurement of lead stored in bone or the calculation of a cumulative blood lead index (CBLI). At a BLL of 40 μg/dL, a CBLI of 1,600 μg-years/dL (the product of a BLL of 40 μg/dL and a 40-year working lifetime) could be achieved. The index is roughly equivalent to a bone (tibia) lead concentration of 40-80 μg/g (2.5-5% of the CBLI). Thus, the committee also sought evidence that would relate these cumulative measures of lead dose to adverse health effects.
The committee obtained data from the US military services to determine current lead exposure on DOD firing ranges. Data collected for the last 5 years show that the OSHA PEL for lead of 50 μg/m3 was frequently exceeded on Army, Navy, and Air Force firing ranges, in some cases by several orders of magnitude. BLL data on firing-range personnel were not available from either the Army1 or the Navy because the available measurements were not linked to job classifications, but the Air Force reported that BLLs of its firing-range personnel were all under 40 μg/dL.
A review of the epidemiologic and toxicologic data allowed the committee to conclude that there is overwhelming evidence that the OSHA standard provides inadequate protection for DOD firing-range personnel and for any other worker populations covered by the general industry standard. Specifically, the premise that maintaining BLLs under 40 μg/dL for a working lifetime will protect workers adequately is not valid; by inference, the OSHA PEL and action level are also inadequate for protecting firing-range workers. The committee found sufficient evidence to infer causal relationships between BLLs under 40 μg/dL and adverse neurologic, hematopoietic, renal, reproductive, and cardio-vascular
1After the committee completed its evaluation and released the prepublication draft of this report, the Army submitted data on BLLs for Department of the Army civilian personnel working at shoot houses. The Army’s submission can be obtained by contacting the National Research Council’s Public Access Records Office at (202) 334-3543 or firstname.lastname@example.org.