An Integrated Exposure/ Pharmacokinetic Based Approach to the Assessment of Complex Exposures

Abstract

A problem in evaluating the hazard represented by an environmental toxicant is that exposures can occur via multiple media such as water, land, and air. Lead is one of the toxicants of concern that has been associated with adverse effects on heme metabolism, serum vitamin D levels, and the mental and physical development of infants and children exposed at very low environmental levels. Effects of lead on development are particularly disturbing in that the consequences of early delays or deficits in physical or mental development may have long-term consequences over the lifetime of affected individuals. Experimental and epidemiologic studies have indicated that blood lead levels in the range of 10-15 micrograms/dl, or possibly lower, are likely to produce subclinical toxicity. Since a discernible threshold has not been demonstrated, it is prudent to preclude development of a Reference Dose (RfD) for lead. As an alternate, the U.S. Environmental Protection Agency (U.S. EPA) has developed the uptake/biokinetic lead model that provides a means for evaluating the relative contribution of various media to establishing blood lead levels in children. This approach will allow for the identification of site- and situation-specific abatement strategies based on projected blood lead levels in vulnerable human populations exposed to lead in air, diet, water, soil/dust, and paint; thus making it possible to evaluate regulatory decisions concerning each medium on blood levels and potential health effects.

Blood lead in U.K. children–time for a lower action level?

“…The impact of low-level lead exposure on children 's development has been a matter of discussion for some time [11]. Recent meta-analysis supports the conclusion that low-level lead exposure has a measurable, although small effect on children's IQ [3,4,12].…”

Levels of heavy metals in outdoor and indoor dusts in Muscat, Oman

“…A house lead dust concentration standard of 1000 mg kg -1 was proposed by Laxen [7]. The correlation between measured dust and blood lead was reviewed by Derosa et al [8] and concluded that for each increase of 1000 ppm of lead in dust, the blood lead increased by 0.2 to 7.2 g dl -1 .…”

Analysis and Source Identification of Heavy Metals in Soils of Central Urban Area of Chongqing, China

“…Scholars began to study heavy metals in the 1980s and 1990s. DeRosa (1991) assessed the effects of lead, an environmental poison, on children's physical or intellectual development. Before 2000, the research focused on the spatial distribution and pollution assessment of heavy metal pollution.…”