Hair, lead exposure determination

Bonithon-Kopp et al. (1986b) investigated another potential marker for lead exposure. Maternal and infant hair lead levels, determined from hair samples taken at birth, were found to be correlated inversely with results on neurobehavioral tests (McCarthy Scales of Children s Abilities) when the children were tested at 6 years of age. Other studies have also reported associations between hair lead levels and behavioral or cognitive test scores, but measures of lead in hair may not accurately reflect internal body burden of lead, and such data should not be used to evaluate internal dose-response relationships (EPA 1986a). 

Lead may be determined in a variety of biological materials such as blood, urine, soft tissues, teeth, bones, hairs, leaves and wood. From the viewpoint of occupational and environmental toxicology the determination of lead in blood is of greatest importance, since the concentration of lead in whole blood (PbB) is considered to be the best indicator of current lead exposure in humans and mammals (Alessio et al., 1979 Ewers et al.. 1991 Lauwerys, 1975 Vahter, 1982 WHO, 1977, 1980). Therefore, the problems of PbB determination are broadly discussed in this chapter, whereas the techniques and problems of lead determination in other biological matrices such as teeth, bones, plant and animal tissues are reviewed to a minor extent. 

Hair lead has also been used to determine exposure. A group of 31 children with learning disability were found to have signiflcantly elevated concentrations of lead and cadmium in hair (Pihl and Parkes, 1977). However, no differences were reported in hair mineral content (including lead) or nutrient uptake in autistic children (Shearer et al., 1982). 

In the most straightforward risk-based approach, epidemiologic studies have developed exposure-response relationships based on biomarker measurements in hair, blood, urine, or other matrices (e.g., mercury, lead) (see Figure 5-2a). The relationships can be applied directly to new biomonitoring data to determine where on the exposure-response curve any person is. That may facilitate an understanding of risk, but it does not analyze sources of exposure, so other techniques (such as environmental sampling and behavioral surveys) may be needed to assess where the exposure came from. 

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