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EXPERIENCE AND REASON:
Jessica L. VanArsdale, Richard D. Leiker, Mel Kohn, T. Allen Merritt, and B. Zane Horowitz
Lead Poisoning From a Toy Necklace
Pediatrics 2004; 114: 1096-1099 [Abstract] [Full text] [PDF]
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[Read P3R] cause vs association
josephq scheller   (14 October 2004)
[Read P3R] Re: cause vs association
Jessica L. VanArsdale   (10 November 2004)

cause vs association 14 October 2004
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josephq scheller,
physician
children's national medical center

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Re: cause vs association

jschelle{at}cnmc.org josephq scheller

the author in footnote 13 misquotes the study of Drs Lanphear et al from the New England Journal. that study shows an association between lead levels <10 and IQ loss, but does not show that lead levels in that range causes IQ loss.

Re: cause vs association 10 November 2004
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Jessica L. VanArsdale,
physician
United Indian Health Services

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Re: Re: cause vs association

drjva{at}earthlink.net Jessica L. VanArsdale

Thank you for raising this important point. Showing an association does not necessarily mean that the relationship is causal. There are several criteria that should be met in order to conclude that a causal relationship exists. These criteria include; finding a statistically significant association, making sure that the findings can’t be explained by reverse causality, bias, or confounding, having internal and external validity, showing a strong association, and having biologic plausibility. The study by Lanphear et al. was well designed and met most of the criteria for causality. Perhaps we need more studies looking at low level lead exposure in order to increase the external validity and then we can determine if there is true causality.