Uhm...
http://en.wikipedia.org/wiki/Ethylmercury
Unlike
methylmercury, ethylmercury has not been found to
bioaccumulate.
[2] The toxicity of ethylmercury is not well studied - exposure standards based on methylmercury (such as those currently recommended by the
United States Environmental Protection Agency) have not been demonstrated to be equivalent for ethylmercury.
[3] Ethylmercury clears from blood with a
half-life of about 18 days in adults. Ethylmercury is eliminated from the brain in about 14 days in infant monkeys. Risk assessment for effects on the nervous system have been made by extrapolating from dose-response relationships for
methylmercury.
[4] Methylmercury and ethylmercury distribute to all body tissues, crossing the
blood–brain barrier and the
placental barrier, and ethylmercury also moves freely throughout the body.
[5] Concerns based on extrapolations from methylmercury caused thimerosal to be removed from U.S. childhood vaccines, starting in 1999. Since then, it has been found that ethylmercury is eliminated from the body and the brain significantly faster than methylmercury, so the late-1990s risk assessments turned out to be overly conservative.
[4] Though inorganic mercury metabolized from ethylmercury has a much longer half-life in the brain, at least 120 days, it appears to be much less toxic than the inorganic mercury produced from mercury vapor, for reasons not yet understood.
[4]
http://www.epa.gov/teach/chem_summ/mercury_org_summary.pdf
I would like to see these studies showing ethylmercury being metabolized into methylmercury...