Karen Wetterhahn

Karen Wetterhahn (October 16, 1948 – June 8, 1997) was a professor of chemistry at Dartmouth College, New Hampshire, who specialized in toxic metal exposure. She made national headlines when mercury poisoning claimed her life at the age of 48 due to accidental exposure to the organic mercury compound dimethylmercury (Hg(CH₃)₂). Protective gloves in use at the time of the incident provided insufficient protection, and exposure to only a few drops of the chemical proved to be fatal after less than a year.

Accident

On August 14, 1996, Wetterhahn, a specialist in toxic metals, was studying the way mercury ions interact with DNA repair proteins, and was using dimethylmercury as a standard reference material for ¹⁹⁹Hg NMR measurements.^[1] Dimethylmercury is a synthetic compound used almost exclusively as a reference standard in a particular type of specialized chemical analysis. Wetterhahn was investigating the toxic properties of another highly toxic heavy metal, cadmium, and was using dimethylmercury as a point of reference.

Wetterhahn would recall that she had spilled several drops of dimethylmercury from the tip of a pipette onto her latex gloved hand. Not believing herself in any immediate danger, as she was taking all recommended precautions,^[2] she proceeded to clean up the area prior to removing her protective clothing.^[3] However, tests later showed that dimethylmercury can in fact rapidly permeate different kinds of latex gloves and enter the skin within about 15 seconds.^[1] The exposure was later confirmed by hair testing, which showed a dramatic jump in mercury levels 17 days after the initial accident, peaking at 39 days, followed by a gradual decline.^[3]

Approximately three months after the initial accident Wetterhahn began suffering brief episodes of abdominal discomfort and noted a significant weight loss. The more distinctive neurological symptoms of mercury poisoning, including loss of balance and slurred speech, appeared in January 1997.^[3] At this point tests proved that she was suffering from a debilitating mercury intoxication.^[4][5][2] She was admitted to the hospital, where it was discovered that the single exposure to dimethylmercury had raised her blood mercury level to 4,000 micrograms per liter, or 80 times the toxic threshold. Her urinary mercury content had risen to 234 µg per liter; its normal range is from 1 to 5 and the toxic level is > 50 μg/L.^[3]

Despite aggressive chelation therapy, her condition rapidly deteriorated; three weeks after the first neurological symptoms appeared, Wetterhahn lapsed into what appeared to be a vegetative state punctuated by periods of extreme agitation. One of her former students said that "Her husband saw tears rolling down her face. I asked if she was in pain. The doctors said it didn't appear that her brain could even register pain."^[2] Wetterhahn was removed from life support and died on June 8, 1997, less than a year after her initial exposure.^[3]

There had been previous documented cases of death due to dimethylmercury poisoning. In 1865, two English laboratory assistants died several weeks after helping to synthesize dimethylmercury for the first time. In 1972, a 28-year-old chemist in Czechoslovakia had suffered the same symptoms as Wetterhahn after synthesizing 6 kg of the compound.^[3][4]

Legacy

Karen Wetterhahn's death shocked not only the entire chemistry department at Dartmouth, but also regulatory agencies, as the accidental exposure occurred despite her having taken all required measures known at that time. These included the use of latex gloves, a fume hood, and adherence to standard safety procedures. After Wetterhahn's mercury poisoning was discovered, her colleagues tested various safety gloves against dimethylmercury and found that the small, apolar molecule diffuses through most of them in seconds, much more quickly than expected. As a result, it is now recommended to wear highly resistant, flexible, plastic-laminate gloves when handling dimethylmercury and other similarly dangerous substances. For increased protection, such thin gloves can be worn under long-cuffed, heavy-duty outer gloves made of, for example, neoprene.^[1][3]

At the time, dimethylmercury was the common calibration standard for ¹⁹⁹Hg NMR spectroscopy because it has certain advantages over the alternatives that exist.^[6] As a consequence of Wetterhahn's accident, safety recommendations^[7] have been revised, and the use of dimethylmercury has been highly discouraged.

Dartmouth College has since established an award in Wetterhahn's name to encourage other women to pursue careers in science. Whenever possible, preference in granting the award is given to a woman.^[8] The National Institute of Environmental Health Sciences also maintains an annual award, for a graduate student or post-doctoral researcher, in honor of Karen Wetterhahn.^[9]

Wetterhahn helped establish Dartmouth College’s Women in Science Project (WISP), which helped to raise the share of women science majors from 13 to 25 percent at Dartmouth College and has become a national model.^[4]

See also

• Mercury poisoning
• Chelation
• Heavy metal (chemistry)

References

External links

• The Trembling Edge of Science by Karen Endicott
• A Tribute to Karen Wetterhahn
• Remembering Karen Wetterhahn
• The Karen Wetterhahn story
• OSHA Material Data Sheet was revised as a result of the Accident