117-124 pq 443 Editorial Neurotoxicity August 26 0637.fm

NEUROTOXIC EFFECTS OF FLUORIDE SUMMARY: This issue of Fluoride contains three new reports on fluoride (F) and neurotoxicity. A study of neurotoxic effects of F in aluminum potroom workers in Iran shows the importance of neurobehavioral testing for the early detection of cognitive impairment in workers occupationally exposed to airborne F. Two studies, from Iran and India, examined the IQ of children drinking high F water (2.38 and 2.45 mg F/L [ppm], respectively), but only one of the two studies showed what was considered a statistically significant result. Attention is thus drawn to the importance of examining confounding and effect-modifying factors. For example, the reported protective effects of magnesium against F toxicity in certain drinking waters, especially when they are soft, need to be considered. Whether there is a threshold at which neurotoxicity from F begins to occur is examined by considering nine other studies showing a significant association between lower IQ or neonatal neurobehavioral impairment and higher oral F intake. If the accumulated evidence of human neurotoxicity from F is viewed dispassionately, two conclusions can be drawn. Airborne F in industrial situations may pose a health risk to workers and may be detected by neurobehavioral testing. The studies currently available on the development of IQ all have their limitations, and although cases can be made, based on a pool of eight reports and a paper by Xiang et al., respectively, for levels of F in drinking water of 0.1 and 0.185 mg F/L being safe for all children, other evidence, from Ding et al., suggests that even a level as low as 0.081 mg F/L is not safe. Thus there is no threshold for F neurotoxicity in drinking water, and the only assuredly safe level is zero.