Lead exposure in a population of Mexican children.

The effects of low lead exposure were investigated in 96 children (7-12 years old) living and studying within a 1 km radius of a lead smelter (exposed population) located in Torreón, Coahuila, México, and compared with 30 children living and studying 4.5 km from the same smelter (control population). Both populations had similar socio-economic conditions. The exposed population showed higher blood lead (PbB) and free erythrocyte protoporphyrin (FEP) concentrations (17.3 +/- 5.6 micrograms dl-1 and 53.9 +/- 46.1 micrograms dl-1, respectively) than controls (PbB, 5.4 +/- 3.1 micrograms dl-1 and FEP, 13.9 +/- 7.3 micrograms dl-1). PbB concentrations were inversely correlated to distance from the smelter (r2 = 0.494). However, in the exposed population, wind direction also had a significant effect on the PbB and urinary lead (PbU) concentrations. The exposed population was divided according to PbB into a high level lead group (PbB > 15 micrograms dl-1), which also showed high FEP concentrations and a low lead group (PbB < 15 micrograms dl-1). Clinically, the high lead group showed a greater incidence of general symptoms (colic, headache, paresthesia, myalgia and dizziness), impairment of some neuromuscular functions (neuromuscular conduction velocity and motor coordination) and a decrease of intelligence quotient (IQ), which was not related with sex or socio-economic status. These results are an evidence of morbidity in children with high PbB concentrations.