Karen E. Wetterhahn, Ph.D., (October 16th, 1948 - June 8th, 1997) was a research professor of chemistry at Dartmouth College and world-renowned expert in the field of metal toxicology. Wetterhahn was born in Plattsburgh, New York, and received bachelor's degrees in chemistry and mathematics from St. Lawrence University in 1970. In 1975, she received her doctorate in inorganic chemistry and physical biochemistry from Columbia University. A year later, she became the first female professor of chemistry at Dartmouth University. Wetterhahn served as dean of graduate studies in 1990, taking on the role of associate dean of the faculty for the sciences from 1990 to 1994, and serving as acting dean of the faculty of arts and sciences in 1995.

On August 14th, 1996, Wetterhahn was working with dimethylmercury, a substance known even then for its potent toxicity. As was the standard lab safety protocol, Wetterhahn wore latex gloves, goggles, and a protective lab coat; as a further precaution, her work with the exposed dimethylmercury was carried out inside a chemical fume hood, to reduce the danger of the chemical's vapors. Using a pipette, Wetterhahn extracted the dimethylmercury from its ampule, placing some inside a sample tube and the rest in a storage vial. In the process, a drop or two of the dimethylmercury dripped from the pipette, landing on Wetterhahn's latex glove. Despite this, there were no visible indications that the chemical had breached the glove's material. After finishing her work, Wetterhahn peeled off her gloves, washed her hands thoroughly, and went home.

Five months after the incident, Karen Wetterhahn began to experience an unusual dizziness and a slurring of her speech. Following the advice of a friend, Wetterhahn admitted herself to the Dartmouth-Hitchcock Medical Center; a neurologist confirmed that her symptoms suggested a case of mercury poisoning. After further blood and urine analysis, the diagnosis was confirmed to be "Severe Mercury Toxicity". Wetterhahn's vision and hearing were both beginning to degenerate at the time she began chelation therapy. On February 6th, 1997, Wetterhahn fell into a coma. She died on June 8th, 1997.

In the wake of Wetterhahn's poisoning, it became clear to her Dartmouth colleagues that the scientific community's understanding of dimethylmercury and the true scope of its toxicity were grossly inadequate. After all, the materials safety data sheet, provided by the supplier from whom Wetterhahn had purchased the dimethylmercury, specifically recommended rubber gloves as suitable protection. Alarmingly, they found that there had been no permeability testing to validate this recommendation in the first place. At the behest of John Winn, chairman of the Dartmouth chemistry department, and Michael Blayney, Dartmouth College's health and safety director, a half-dozen or so different gloves from Wetterhahn's lab were sent to be tested. The results indicated that dimethylmercury took less than fifteen seconds to permeate latex gloves; the other gloves tested were, likewise, determined to be useless as a means of protection. Only a multi-layered laminate glove proved effective, withstanding dimethylmercury for up to four hours. The story of Wetterhahn's accident, the glove permeability data, and the safety recommendations derived from it were published in the May 12th, 1997 edition of Chemical and Engineering News.

Of course, the erroneous recommendation was really, itself, the symptom of a more fundamental misunderstanding within the scientific community, regarding dimethylmercury's potential toxicity. The disparity, explained Winn, can be plainly seen between typical mercury poisoning (in which 50 micrograms of mercury per liter of blood constitutes the toxic threshold) and an analysis of Wetterhahn's blood, which was found to contain 4,000 micrograms per liter—in other words, 80 times the toxic threshold, produced from only a drop or two of the substance. And yet, despite its overwhelming toxicity, dimethylmercury had only been involved in two fatal accidents prior to Wetterhahn's. The first incident, in 1865, resulted in the deaths of the two English chemists responsible for synthesizing the compound; both died from exposure to the chemical’s fumes. The second accident occurred in 1970, leading to the death of a Czech scientist. This discrepancy between the compound’s lethality and its history led, at first, to an air of incredulity amongst the scientific community in the aftermath of Wetterhahn's accident; with dimethylmercury's widespread use throughout the last one-hundred years, it seemed highly unusual that more people hadn't fallen victim to it's toxicity.

At the time, dimethylmercury was still widely used by scientists, particularly in experiments examining the effects of mercury on living cells. To analyze these effects, scientists observe the bonded changes within the cell's structure through the use of an NMR (nuclear magnetic resonance) spectrometer, which returns a pattern of frequencies representing the molecule's form. However, a change in the cell's structure is only noticeable when compared to the frequencies of a standard, which is, furthermore, necessary to calibrate the machine before testing. Dimethylmercury, despite its toxicity, is an ideal standard for mercury testing, and it was for this reason that Karen Wetterhahn, on the day of the accident, had been preparing a sample of dimethylmercury. In a last, bitter irony, Wetterhahn had previously used mercury chloride salts as the standard for her work with the NMR spectrometer, but opted to use the dangerous, but more accurate dimethylmercury only after expressing dissatisfaction with the mercury chloride results. After completing the experiments a second time with the dimethylmercury standard, however, Wetterhahn was surprised to find that the results only confirmed the accuracy of her initial tests.

Yet, inspite of the tragic circumstances of her death, it's Karen Wetterhahn's life and work which continues to exert a lasting influence on both Dartmouth and the scientific community. Within her field, Wetterhahn was primarily known for her work in chromium carcinogenesis, of which she was one of the world's leading authorities. Among her contributions, she introduced the concept known as the uptake-reduction model, to explain the process by which chromium damages DNA. And, at the time of her death, she had authored over 85 research papers. In 1991, Wetterhahn established the Women in Science Project alongside Carol Miller, assistant dean of engineering, to address the disproportionate amount of female students dropping out of science related fields. As a result, the percentage of female science majors has doubled in size. She further served as an officer for the Women in Cancer Research Society, as well as a past officer in the American Association for Cancer Research. As to her character, much has been said about her personal enthusiasm, her good-natured approach to collaboration, and her passion for science. John Winn, in remembering his colleague, remarked that "I always heard her laughing – I never heard her yelling. For the most part, I’ll remember her giggle"(8). Karen Wetterhahn is survived by her husband Leon Webb, and her two children Leon Jr. and Charlotte.

In memory of Karen Wetterhahn, Dartmouth has established a graduate fellowship in chemistry and an annual faculty achievement award in her honour. Furthermore, both a library reading room and the annual undergraduate science symposium have been dedicated and named in her memory. Perhaps even more subtly, her influence can be felt within the many chemistry classrooms of Dartmouth, a fact acknowledged by chemistry lab coordinator Sally Hair: "Most students wear gloves most of the time now, even when they don’t need to. We’re spending a lot on gloves. We’re going through hundreds of pairs per week"(2).


  1. "The Trembling Edge of Science" by Karen Endicott
  2. Women in Medicine: An Encyclopedia by Laura Lynn Windsor (2002)
  3. "Handling dimethylmercury" by Michael B. Blayney, John S. Winn & David W. Nierenberg, Chemical & Engineering News (May 12th, 1997)
  4. "Colleagues Vow to Learn From Chemist's Death" by Carey Goldberg, the New York Times (October 3rd, 1997)
  5. "Dartmouth Researcher Dies from Mercury Poisoining" Associated Press (June 11th, 1997)
  6. "A Tribute to Karen Wetterhahn" Dartmouth
  7. "In Memoriam Karen E. Wetterhahn, Ph.D. 1948−1997" American Chemical Society (September 15th, 1997)
  8. "Remembering Karen Wetterhahn" by Laura Sternick, Dartmouth (May 16th, 2008)

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