Methylmercury Exposure and Neurotoxicity

The Comment in a Peer-Reviewed, Scientific Journal:

Kathryn R. Mahaffey. Journal of the American Medical Association (JAMA). Vol. 280. pp: 737-738. 1998.

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The Purpose of this Comment in a Peer-Reviewed, Scientific Journal:

• The author is responding to the peer-reviewed, scientific paper “Effects of Prenatal and Postnatal Methylmercury Exposure From Fish Consumption on Neurodevelopment: Outcomes at 66 Months of Age in the Seychelles Child Development Study” by Drs. Davidson, Myers, Cox, and other fellow Seychelles Child Development Study (SCDS) researchers in this same 1998 issue of the Journal of the American Medical Association (JAMA).
  
• Dr Davidson and his fellow SCDS researchers report they do not believe that eating methylmercury-contaminated fish caused any nervous system or mental development bad affects in the many children they studied in the SCDS. These particular children were exposed in the womb - and again after being born - to methylmercury in the fish eaten by them and their mothers while pregnant with this child.

Some Background, Methods, Results, Caveats, and Other Select Points:

• This comment was published in a peer-reviewed, scientific journal in 1998.
  
• Comments are not peer-reviewed before they are published in peer-reviewed, scientific journals.
  
• Although the author is employed by the Environmental Protection Agency (EPA), her comments do not necessarily reflect any EPA policies.
  
• All fish contain some methylmercury.
  
• The author states that the unborn child is more at risk from extreme methylmercury poisoning than are adults and describes the consequences of the three episodes of extreme methylmercury poisoning that occurred globally.
  
• The author also revisits the results from the Seychelles Child Development Study (SCDS) that differ from those from the Faroe Islands study. These two, large, ongoing, methylmercury-and-fish-eating studies are respectively run by the University of Rochester School of Medicine and Dentistry (SCDS) and the Harvard University (Faroe Islands).
  
• The author believes that whenever scientists attempt to determine the lowest level of methylmercury that can harm people, the amount tested always in part determines the methylmercury level reported as being the lowest level considered harmful to specific populations.
  
• The author believes that the Faroe Islands researchers used better tests on the people they studied than did the SCDS researchers. The author states that she believes these better tests can identify slight brain and mental malfunctions that are not detectable by the tests used by the SCDS researchers.
  
• The author takes issue with Dr. Davidson’s findings that the neurological effects reported in some of the people studied in the Faroe Islands may be caused in part or in full by the PCBs and other harmful chemical pollutants found in the seafood consumed by the Faroe Islanders.
  
• The author notes that some of the SCDS children with the highest methylmercury exposure in-the-womb - and after being born - had higher test scores than some of the children with lower methylmercury levels. The author finds these results to be seemingly contradictory. These results cause the author to further question the SCDS researchers’ interpretation of their SCDS testing results.
  
• The author notes that the certain types of fish usually eaten by Americans have an average methylmercury level of about 0.13 parts per million (13 parts of methylmercury eaten for every 100 million parts of fish meat eaten). The author continues that some U.S. freshwater fish have much higher methylmercury levels than found in the average commercially-available fish (which tend to be saltwater fish from the oceans.) The author then details some of the higher methylmercury levels in some of the freshwater fish caught and eaten by Americans. Again, proving that eating fish with high, methylmercury levels is bad for you.
  
• The author also notes that many U.S. bodies of water with high methylmercury levels also have high PCBs levels. The author does not mention that Americans eat fish caught from all over the world and not just from U.S. bodies of water. She also does not specify if these U.S. bodies of water are only freshwater lakes, rivers, and streams. The author states that fish eaten in the Seychelles Islands are believed to have low PCBS levels.

A Bottom Line:

• The author presents her opinion that the scientific findings reported by Dr. Davidson and his fellow SCDS researchers in their peer-reviewed, scientific paper “Effects of Prenatal and Postnatal Methylmercury Exposure From Fish Consumption on Neurodevelopment: Outcomes at 66 Months of Age in the Seychelles Child Development Study” are preliminary and require additional study.
• The author states that all women of childbearing age who eat fish every day must avoid fish contaminated with high methylmercury levels and / or high levels of any other bad chemical pollutants.

Find This Scientific Paper for Your Review:
Methylmercury Exposure and Neurotoxicity. Journal of the American Medical Association (JAMA). Vol. 280. pp: 737-738. 1998.