Program [NTP]”. In keeping with its charge, the committee initially evaluated key literature presented in the NTP’s 2012 Monograph on Health Effects of Low-level Lead, the EPA’s 2006 Air Quality Criteria Document [AQCD] for Lead Final Report, the 2012 EPA’s Integrated Science Assessment for Lead (Second External Review Draft), the International Agency for Research on Cancer (IARC) monograph Inorganic and Organic Lead Compounds (IARC 2006), and the 2004 and 2011 editions of the NTP Report on Carcinogens. The committee then considered studies that were not included in those reviews. During this step, the committee gave greater weight to other systematic reviews and studies that included meta-analyses.
The committee used additional considerations to narrow its work. Health-effects data on BLLs below 40 μg/dL were primarily considered because the current OSHA standard aims to maintain BLLs below that concentration. Whenever possible, the committee based its conclusions on occupational and other studies of relevance to DOD personnel that work at firing ranges. Special consideration was given to women who might be pregnant or nursing because of the well-known effects of lead on the developing nervous system. The committee also favored studies that considered potential covariates in their statistical analyses; these included tobacco use, alcohol consumption, and coexposure to other metals and chemicals. The committee’s conclusions emphasized outcomes associated with clinical disease rather than early biologic effects. For example, the committee considered decrements in circulating hemoglobin to be more important than increases in zinc protoporphyrin. In reaching its conclusions, the committee considered the weight of evidence and relied most heavily on findings of lead-induced adverse health effects that had been replicated in multiple peer-reviewed studies.
The committee’s conclusions are based on noncancer end points. Although IARC, NTP, and EPA have identified lead as probably carcinogenic in humans, such findings were based largely on studies of laboratory animals. The available human studies on cancer were insufficient for the committee to draw a conclusion about BLLs that might be associated with cancer in humans.
The primary purpose of the Occupational Safety and Health Act (29 USC 655 et seq) is to ensure, to the extent possible, safe and healthful working conditions for every American worker over his or her working lifetime. OSHA’s lead standard requires that a worker who has a single BLL over 60 μg/dL or three BLLs averaging over 50 μg/dL be removed from performing lead work until his or her BLL is under 40 μg/dL on two occasions. Thus, the current OSHA lead standard recognizes a level of concern for workers who have BLLs of 40-60 μg/dL or higher. The committee therefore focused its attention on whether lead