Schematic of a hypothetical workers dose over time

FIGURE 3-2 Schematic of a hypothetical worker s dose over time. Used with permission of Brian Schwartz, Johns Hopkins Bloomberg School of Public Health. 

Given the importanee of enmulative lead dose to health (discussed in Chapters 4 and 5) and the laek of wide availabihty of XRF systems for measuring bone lead, this argues that more frequent longitudinal monitoring of BLLs, with attention to the CBLI over time, would have much greater utihty than heretofore required under the OSHA lead standard. 

The relationship between air lead concentration and BLL is complex. Exposure to lead can occur through multiple pathways. BLL is the exposure metric most commonly described in association with health effects in humans, and lead exposure is typically assessed by using a pharmacokinetic model to relate air (or dietary) exposure concentratiorrs to BLLs. The committee s goal was not to review in depth the various dosimetry models available for lead but to explore how dosimetry models were used in the development of the OSHA generd industry lead standard and to evalirate the models and their assumptions (see Table 3-1). 

TABLE 3-1 Assumptions Used by Occupational Safety and Health Administration for Center for Policy Alternatives Model and Committee s Evaluation 

Particle size First 12.5 pg/m of airborne lead consisted of lead particles with an aerodynamic diameter of 1 pm remainder consisted of larger particles ( 1 pm) that would be deposited in upper respiratory tract. Size of lead aerosol can influence deposition and absorption of lead from respiratory tract and delivery to systemic bloodstream (Froines et al. 1986 Park and Paik 2002). For example, lead fumes are more easily absorbed from lungs and result in higher BLLs than inhalation of larger lead particles. Smaller lead particles also appear to be more soluble regardless of chemical form of dust (Spear et al. 1998). 

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