Neurotoxicity of Lead in Human Populations

Full understanding of this broad exposure—toxic outcome relationship did not occur overnight. Evolving comprehension is readily apparent in the historical record of lead and its various human health hazard relationships across decades and centuries (see previous chapter). This chapter, in common with the other chapters on toxicological harm from Pb exposures in humans, is not intended to be an encyclopedic recapitulation of the neurotoxicity record of Pb exposures in children, adults, and experimental test animals and wildlife. Rather, these chapters are distillations of the most reliable health science literature, i.e., literature that is most useful for addressing the principal end uses of the monograph the science of lead as it elucidates and propels both human health risk assessment and regulatory initiatives. 

The criticality concept, first articulated by Nordberg (1976), makes for ease of presentation within the rationale of what is most immediately 

Trace Metals and other Contaminants in the Environment, Volume 10 

Current weight-of-evidence approaches for Pb show that we cannot assume that a single somatic target exists for Pb while all other target sites function with littie or less sensitive responses at a given level of human exposure. Lead produces low-dose toxicity in multiple body sites and the respective threshold doses, i.e., critical doses, for onset of toxicity do not differ greatly. 

There are a number of aspects of lead neurotoxicology presented in this chapter. The first is the clear distinction between Pb toxicity observed in young children qualitatively and quantitatively and what comprises the typical case for older children and adults. That is, the nature of Pb-associated neurotoxic injury is different and the onset of neurotoxic injury in children is known to occur at lower exposures than in adults and older children. This chapter is consequently divided into sections dealing separately with childhood versus adult Pb toxicity in humans. 

---