We have been informed that there a number of errors in the paper detailed below.
Negative Confounding in the Evaluation of Toxicity: The Case of Methylmercury in Fish and Seafood
Anna L. Choi, Sylvaine Cordier, and Philippe Grandjean
Please see below for the details.
Abstract
In observational studies, the presence of confounding can distort the true association between an exposure and a toxic-effect outcome, if the confounding variable is not controlled for in the study design or analysis phase. While confounding is often assumed to occur in the same direction as the toxicant exposure, the relationship between the benefits and risks associated with fish and seafood consumption is a classic example of negative confounding: the exposure to methylmercury occurs with fish and seafood, which are also associated with beneficial nutrients, thereby counteracting the signs of mercury toxicity.
Page 882
This evaluation considered the effects of DHA supplementation of pregnant and lactating women, the effects of DHA and arachidonic acid supplementation of preterm infants on visual development at <6 months, and effects of high-dose DHA supplementation of term infants on visual development during the first year of life; we found no supporting evidence, inconclusive evidence, and consistent evidence, respectively.
Page 886
Reference made to (Grandjean, 2007) should have read:
(Grandjean and Budtz-Jϕrgensen, 2007)
Page 887
Without controlling for the beneficial aspects of breastfeeding, the toxicity of PCBs and dioxins on neurodevelopment will be underestimated, as a result of negative confounding. Likewise, the benefits of breastfeeding may appear less when the effects are quenched by contaminant exposures.