To the Editor: The follow-up study by Needleman et al. (Jan. 11, issue)1 purports to demonstrate enduring cognitive and neurobehavioral effects of relatively low levels of exposure to lead in children previously studied in 1975 through 1978.2 What it may demonstrate with equal if not greater likelihood are the enduring effects of social, developmental, and medical risk factors associated with cognitive and neurobehavioral deficits. The issue of confounding factors in this complex subject has been highlighted previously,3-5 yet Needleman et al. aver that the persistent toxicity of lead [at relatively low levels] was seen to result in significant and.
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