How dangerous are low (not moderate or high) doses of lead for children's intellectual development?

This paper addresses the points raised by five groups of scientists who wer e invited to respond to my article on the relationship of low blood lead to IQ loss. I dealt with these comments as a scientist who believes that the case is not closed on this topic, as some respondents believe, but that deb ate is healthy and can move the field to the next level. The criticisms abo ut the measurement of parents' IQ, multiple comparisons, the linearity of t he lead-IQ relationship, and the societal consequences of a few points of I Q loss appear weak in the face of an array of evidence that bears on these topics. However, criticisms about my emphasis on the need to control for a wide variety of potential confounders has validity. Ultimately, however, th e case for the relationship of low blood lead to IQ loss seems to rest tenu ously on data obtained from samples that included numerous subjects with mo derate to severe levels of blood lead. (C) 2001 National Academy of Neurops ychology. Published by Elsevier Science Ltd.