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Mercury Poisoning Kills Lab Chemist

In a tragic end to a story that began last summer, an internationally known research chemist at Dartmouth College, Karen Wetterhahn, died on Sunday of poisoning from a few drops of a potent neurotoxin she spilled on her lab glove 10 months ago. She was 48.

Wetterhahn studied the effects of heavy metals on living organisms. The accident occurred last August when she was attempting to measure the nuclear magnetic resonance spectrum of dimethyl mercury, which is used as a reference material for other toxic compounds. "She was taking what any of us would have considered prudent and reasonable precautions," says John Winn, head of the Dartmouth chemistry department. She used a hood to protect herself from fumes and was wearing a face shield and latex gloves when she spilled a drop or so of the colorless, highly volatile compound. It apparently passed through the glove almost instantly. "I don't think any of us recognized" that the compound was so penetrating, says Winn.

Wetterhahn reportedly did not regard the incident as serious at the time. But 5 months later, she began having trouble with balance, speech, vision, and hearing. She was hospitalized and on 28 January was diagnosed with mercury poisoning. Her blood levels were 80 times higher than the standard threshold for toxicity. Three weeks later, she went into a coma.

Dimethyl mercury, first synthesized in 1865, easily penetrates biological membranes and, in humans, turns into methyl mercury--a former crop fumigant. The World Health Organization outlawed the chemical for use as a fungicide in 1974 after an episode in which it killed 600 people in Iraq. Despite its sinister nature, this is only the fourth lab death associated with the compound.

Winn says accepted lab procedures call for the use of gloves in handling dimethyl mercury, but don't necessarily specify what kind. So last month, in a letter in the 11 May Chemical & Engineering News, he and two colleagues warned that latex gloves are "not suitable for significant, direct contact with aggressive or highly toxic chemicals" and recommended that two pairs of gloves, one of them laminated, be worn. In addition, says Winn, "We're trying to urge the chemical community to establish a safer substitute."