Dimethylmercury ((CH3)2Hg) is a flammable, colorless liquid, and one of the strongest known neurotoxins. It is described as having a slightly sweet smell, though inhaling enough fumes to notice this would involve significant exposure to the chemical. It is extremely dangerous, with absorption of doses as low as 0.001 mL being fatal. The high vapor pressure of the liquid means that any spillage will result in dangerous levels of exposure to the fumes for those nearby. The molecule adopts a linear structure.
Dimethylmercury crosses the blood-brain barrier easily, probably due to formation of a complex with cysteine. It is eliminated from the organism very slowly, therefore it has tendency to bioaccumulate. The symptoms of poisoning may be delayed by months, possibly too late for effective treatment.
Dimethylmercury passes through latex, PVC, butyl, and neoprene rapidly (within seconds), and is absorbed through the skin. Therefore, most laboratory gloves do not provide adequate protection from it, and the only safe precaution is to handle dimethylmercury while wearing highly resistant laminated gloves underneath long-cuffed neoprene or other heavy-duty gloves. A long face shield and work under a fume hood are also indicated.
The toxicity of dimethylmercury was highlighted when a well-known chemist, Karen Wetterhahn, died several months after spilling a few drops of this compound on her latex-gloved hand.