Role of Chronic Low-Level Lead Exposure in the Ætiology of Mental Retardation

Blood lead levels and growth status of children

“…Furthermore, brain growth and develo ment of other nervous tissue is impeded g y decreased myelination caused by Pb-associated metabolic abnormalities (Sauer et al, 1970). Mental retardation (Beattie et al, 1975;Choate, 1972, 1975;Bellinger et al, 1986Bellinger et al, , 1987Pocock et al, 1987;Sachs et al, 19781, hysical owth deficiencies (Habercam et a f , 1971; g u w e r s et Mahaffey et al, 1986;Schwartz et al, 1986), neurobehavioral abnormalities (David et al, 1972;Faust and Brown, 1987;Schwartz and Otto, 1987;Wigg et al, 19881, fine motor skill deficiencies (Needleman et al, 1979;Ernhart et al, 19891, and slowed nerve conduction (Landrigan et al, 1976) are often found in children with elevated Pb levels. These are similar to toxic sym toms observed in adults who have…”

Evaluation of the carcinogenic risk of chemicals to humans

“…The water lead content was significantly higher for the retarded group, and the probabilty of 378 IARC MONOGRAPHS VOLUME 23 mental retardation was significantly increased when water lead exceeded 800 I1g/1. Blood lead levels were also significantly higher in the retarded groupe It was concluded that lead contamination of water may be one factor in the multifactorial etiology of mental retardation and that every effort should be made to reduce the lead content of drinkingwater (Beattie et al, 1975) (The Working Group noted that the current water lead levels may not have reflected those encountered by the children in utero or in the first year of IifeJ. Blood lead concentrations were measured retrospectively in the blood contained on cards used for testing for phenylketonuria in the first two weeks of life taken from a group of 77 children with mental retardation of unknown etiology and 77 controls; 24 pairs were evaluated. There was a highly significant trend towards higher blood lead concentrations in mentally retarded children.…”

Toxicological Properties of Lead

“…Thus, as many of the controls may have been at high risk for lead, and Kotok's data must be considered inconclusive (43). Other studies suggesting a causative association of lead exposure with mental impairment have been equally inconclusive (14,(44)(45)(46)(47).…”