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Declining Blood Lead Levels and Cognitive Change in Children

Claire B. Ernhart, PhD
JAMA. 1993;270(7):827-828. doi:10.1001/jama.1993.03510070049019.
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To the Editor.  —The article by Ruff et al1 received extensive coverage in the media. It is not unusual for reporters to misconstrue research; in this case, however, they ignored the most important result. There was no statistically significant effect of chelation for children with blood lead levels in the range of 1.21 to 2.66 μmol/L (25 to 55 μg/dL). This was true for blood lead level as well as for cognitive development.The finding is particularly remarkable because assignment to chelation was not random but was based on a positive lead mobilization test. With this design, the treated group would have initially high blood lead levels and, on the basis of regression toward the mean alone, should have had a greater blood lead level decrease than nonchelated children. The lack of effect of chelation for this range of blood lead level is extremely important because of the costs


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