Neurocognitive effects of chronic lead intoxication in Andean children.

Lead (Pb) intoxication in children has been associated with neurodevelopmental disabilities which may result in motor and cognitive impairment. We conducted blood lead (PbB) measurements, neurological examinations and cognitive tests on children living in Ecuadorian villages where Pb is used extensively in the glazing of ceramics. Group I consisted of 55 children with a mean PbB level of 48.0 microg/dl (SD: 26.4, range: 9.2-119.1 microg/dl) who received PbB tests and complete neurological examinations. An appreciable number of the children with elevated PbB levels were normal on specific components of the neurological examination. Among the children who showed neurological deficits, higher PbB levels were associated with abnormal tendon reflexes, finger tapping, visual pursuit, size discrimination, draw-a-person, and math calculation skills. Group II consisted of 41 children with a mean PbB level of 47.4 microg/dl (SD: 22.0, range: 6.6-84.7 microg/dl) who were administered Raven's Coloured Progressive Matrices (RCPM) non-verbal reasoning test. Performance on RCPM was abnormal in 22 (53.7%) of 41 children. Children with abnormal RCPM scores had higher PbB levels (t-test: P=0.030). There was a significant inverse correlation between RCPM scores and PbB levels for children ages 9 years and older (r=-0.618, P=0.011). Males had higher mean PbB levels as a function of age than females (t-test: P=0.037), and more males showed neurocognitive deficits. The results demonstrate a range of neurological responses in children with chronically elevated PbB levels from apparent exceptional neuro-physiological tolerance of PbB intoxication, to some fine motor and cognitive deficits.