Ethylmercury

Synthesis and structure

Ethylmercury (C2H5Hg+) is a substituent of compounds: it occurs as a component of compounds of the formula C2H5HgX where X = chloride, thiolate, or another organic group. Most famously X = the mercaptide group of thiosalicylic acid as in thiomersal. In the body, ethylmercury is most commonly encountered as derivatives with a thiolate attached to the mercury. In these compounds, Hg(II) has a linear or sometimes trigonal coordination geometry. Given the comparable electronegativities of mercury and carbon, the mercury-carbon bond is described as covalent.

Toxicity

The toxicity of ethylmercury is well studied. Risk assessment for effects on the human nervous system have been made by extrapolating from dose-response relationships for methylmercury. In monkeys, it clears from brain tissue with a half-life of 24 days and blood in 7 days.

It is a fungicide but has been banned from use in the U.S. on food grain and even on seeds only used to grow crops.

Public health concerns

Main article: Thiomersal and vaccines

Concerns based on extrapolations of the effect of methylmercury caused thimerosal to be removed from U.S. childhood vaccines in 1999, but it remains in use in all multi-dose vaccines and flu shots (though many single-use vaccines without thimerosal are available). Researchers have argued that risk assessments based on methylmercury were overly conservative in light of observations that ethylmercury is eliminated from the body and the brain significantly faster than methylmercury.

References and notes

References

1. {{Greenwood&Earnshaw2nd
2. Elschenbroich, Christoph. (2016). "Organometallics". John Wiley & Sons.
3. (2004). "Mercury exposure in children: A review". Toxicology and Applied Pharmacology.
4. (October 2007). "Mechanisms of mercury disposition in the body". American Journal of Industrial Medicine.
5. (2012-07-27). "Weekly Epidemiological Record, vol. 87, 30 (pp 277–288)".
6. Burbacher, Thomas M.. (2005). "Comparison of Blood and Brain Mercury Levels in Infant Monkeys Exposed to Methylmercury or Vaccines Containing Thimerosal". Environmental Health Perspectives.
7. "Organic Mercury--TEACH Chemical Summary--U.S. EPA, Toxicity and Exposure Assessment for Children's Health".
8. Research, Center for Biologics Evaluation and. (2019-04-05). "Thimerosal and Vaccines". FDA.