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CHRONIC LOW-LEVEL LEAD EXPOSURE REDUCES CHILDREN'S IQ.

There is controversy about whether low-level lead exposure leads to learning disabilities and mental retardation in children. To study the effects of low-level lead exposure, Australian researchers have followed a group of children raised in a lead smelting community since 1979, collecting data on a large variety of demographic and biologic variables that are known to affect IQ. An earlier report described adverse developmental effects from low- level lead exposure at ages 2 and 4; this new report, involving 494 children at age 7, shows that the impairment persists. (see Journal Watch accession number 880902002).

IQ was inversely associated with both the mother's antenatal blood lead concentration and the children's own blood lead concentrations (particularly at 15 months to 4 years of age), after adjusting for many factors (including socioeconomic status, birth weight, and parents' level of education). Regression analysis showed that an increase in blood lead concentration from 10 to 30 micrograms/dl was associated with a 4.4 point reduction in IQ.

Some critics have argued that associations between low- level lead exposure and reduced IQ are spurious, reflecting confounding social or biologic factors. Because this study adjusted for a wide range of confounders, it strongly suggests that long-term low-level lead exposure directly impairs IQ in children.

— ALK

Published in Journal Watch General Medicine October 30, 1992

Citation(s):

Baghurst PA et al. Environmental exposure to lead and children's intelligence at the age of seven years: the Port Pirie Cohort Study. N Engl J Med 1992 Oct 29 327 1279-1284.

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