Questions and Answers
Question #44


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Questions and Answers

 

Question # 44

Are you aware of any known correlation between in utero mercury exposure and NLD?


Answer (courtesy of Dr. Roberta F. White):

The evidence on mercury is mostly based on methylmercury.

If mercury exposure is from thimerosol, which is used in injections, then we are talking about ethylmercury, which is less neurotoxic. The research to date on ethylmercury does not provide much support for cognitive deficits associated with early developmental exposures at levels experienced in the US (or the Faroe Islands).

If exposure was to methylmercury from seafood consumption, there is much more evidence. The epidemiologic data suggests that prenatal MeHg exposure is most associated with deficits in language and attention at ages 7 and 14. There is other evidence suggesting a decrement in IQ. I know of no information on relationships to diagnostic syndromes such as ADHD or NLD. There is some evidence from the Faroes (and South America) that prenatal exposure affects visual memory (Bender recall, S-B Copying Test) but the children in the Faroes did very well on tests like Block Design. I have some very pilot level imaging data that suggest brain reorganization of function may occur with prenatal MeHg exposure, but I do not at all see a consistent “right hemisphere” pattern.

In general, exposures to metals like lead early in development can be related to a number of syndromes, and my clinical impression is that the consequences of such exposures are often related to inherited vulnerabilities (e.g., verbal learning disabilities or language disorders in children whose parents are relatively weak in verbal abilities).

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