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From the campaign biography of Dr. Jill Stein, U.S. 2012 presidential candidate for the Green Party:

[Jill] played a key role in the effort to get the Massachusetts fish advisories updated to better protect women and children from mercury contamination, which can contribute to learning disabilities and attention deficits in children.

I appreciate less mercury in my food, but this is the first time I've heard the claim that it can lead to "attention deficits." Is this link supported by scientific studies?

  • 1
    sounds a bit like the "vaccination causes autism" claims. – Baarn Jan 8 '12 at 20:58
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    Not really. Mercury is the proposed (and debunked) mechanism by which vaccines were said to cause autism. But mercury is actually a poison, and it is actually found in unhealthy concentrations in seafood. Debunking "vaccination causes autism" means you should get vaccinated. Debunking "mercury-heavy fish causes ADHD-I" doesn't mean you should start eating mercury-heavy fish. – user792 Jan 8 '12 at 21:19
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Yes, there are studies which show a correlation between methylmercury exposure and attention deficits.

One of the 'cornerstone' mercury studies was performed in the Faroe Islands by Grandjean, et al 1999, (Methylmercury exposure biomarkers as indicators of neurotoxicity in children aged 7 years ) where they followed a cohort of 917 Faroese children from birth until the age of 7, which reported

Outcome variables were the results of neuropsychologic examination earned out in 1993-1994 at age 7 years. After adjustment for covariates, the cord-blood concentration showed the clearest associations with deficits in language, attention, and memory."

They further suggest that:

the greatest susceptibility to methylmercury neurotoxicity occurs during late gestation, while early postnatal vulnerability is less, and they suggest that the time-dependent susceptibility may vary for different brain functions

As a comparative note to the Ha, et al, 2009 study given above, it is interesting to note that the Faroese children had at birth a geometric mean Hg cord blood concentration of 22.9 μg/l, and at aged 7 years 8.82 μg/l, notably higher than the Korean children studied.

  • As with all questions of this type the critical issue isn't whether there is ever an association but at what level does it become significant? – matt_black Jan 10 '12 at 14:43
  • Given the results of this study a cord blood of 22.9 μg/l Hg is a significant amount of Hg - one reason why pregnant women are told to not eat fatty fish. There's another Danish study (ncbi.nlm.nih.gov/pubmed/17631607) which links fatty fish consumption with reduced fetal growth. – Darwy Jan 10 '12 at 22:50
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    Remember, METHYLmercury is different than ETHYLmercury. :) Just in case the anti-vax pro-disease nutters show up! – Larian LeQuella Jan 12 '12 at 1:34
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There doesn't seem to be connection at least not in Korean children:

The blood lead level showed a significant positive association with the Conners’ ADHD score (beta = 0.50, p < 0.0001). However, the blood mercury levels were not found to be significantly associated with ADHD symptoms in children. The geometric mean mercury concentration in the blood was 2.4 μg/l. (Ha et al, 2009)

I found another study done with Chinese children(Cheuk & Wang, 2006) that found an association, however it appears to have been retracted. "for reasons of mistakes in the methodology and the presentation of study cohorts.".

  • Good finds. I would expect any confirming papers to be published several years before that - assuming her biography is chronological, 2002 and earlier. – user792 Jan 9 '12 at 16:04

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