World-renowned chemist Karen Wetterhahn died after receiving a toxic dose of dimethylmercury, even though she was following proper safety precautions.
Chemical toxicity is measured using a number called the median lethal dose (LD50), which describes the dosage required to kill half of a tested population. The LD50 of dimethylmercury (PDF) is 50 micrograms per kilogram of body weight, which means a 130-pound woman (59 kg) could be killed by about 3 mg of the substance. Wetterhahn accidentally got a few drops of dimethylmercury on her glove-covered hand. But, the glove provided no protection. The chemical seeped through, touched her skin and entered her body. A few months later, she began to experience symptoms of mercury poisoning, such as trouble with balance, as well as impaired speech, vision and hearing. She then slipped into a coma and died, becoming the fourth laboratory victim of dimethylmercury.
Source: Science Now