Geochemical and man-made sources of lead and human health.

Multiple sources of Pb have been identified for human populations, but there is little agreement as to their relative significance. Marked regional geochemical anomalies in the distribution of Pb have been identified and, in one district, their impact on rural communities has been determined. The absorption of ingested Pb is modified by its chemical and physical form, by interaction with dietary minerals and lipids and by the nutritional status of the individual. Studies on children of various ethnic groups have demonstrated differences in soft tissue Pb burdens which may in part have a nutritional basis. Erythrocyte protoporphyrin determinations suggest that metabolic disturbances attributable to Pb may occur at soft tissue burdens previously regarded as acceptable. The problem of defining an adverse health effect in relation to environmental sources of Pb is discussed.