More on working with dimethylmercury

Taft Y. Toribara and Thomas W. Clarkson, University of Rochester School of Medicine & Dentistry, Rochester, N.Y.
David W. Nierenberg, Dartmouth Medical School, Hanover, N.H.

Chemical & Engineering News (16 June 1997) Vol. 75, No. 24, p. 6.

We would like to further alert any users of dimethylmercury to the possibility of extremely hazardous exposure to small quantities of this chemical, which might be spilled in a laboratory (C&EN, May 12, page 7).

Recently, our laboratory received biological samples from a victim of severe dimethylmercury poisoning for the purpose of determining the sample's mercury content (see page 11). An event in our laboratory alerted us to the potential extreme hazard from the compound.

During the calibration of a mass spectrometer, the operator used a pipette with a plastic tip to transfer dimethylmercury from its original glass vial to a Pyrex glass vial equipped with a crimp top for a Teflon-lined silicone stopper. The transfer was done in a fume hood. After the transfer, he discarded the plastic tip in a nearby wastebasket. In a short time, the instrument, which can detect nanogram quantities of mercury, showed measurable quantities in the air surrounding the instrument.

This event demonstrated the high volatility of dimethylmercury and aroused our curiosity concerning the volatility of any amount that might be spilled accidentally. The vapor pressure of dimethylmercury at 23.7 C is 58.8 mm. [J. Inorg. Nucl. Chem.,20, 340 (1961)]. Using that figure, it is estimated that a cubic meter of saturated air could hold more than 600 g of mercury. This indicates that any small quantities spilled evaporate rapidly, and that people nearby would be exposed to levels exceeding the Occupational Safety & Health Adminstration's time weight air sample for occupational exposure of 0.01 mg per cubic meter.

The dialkyl mercury compounds were first synthesized in the mid-19th century[ Q. J. Med., N.S.9, 193 (1940)]. An accidental spill soon followed the discovery, resulting in two fatalities. In a later case, two secretaries working some 15 feet from a leaking container of diethylmercury in a large warehouse were fatally poisoned [Canad. J. Public Health, 43, 1580 (1943)]. Another case involved a chemist who synthesized about 6,000 g of dimethylmercury in a three-month period [Int. Arch. Arbeitsmed., 33, 323 (1974)]. Shortly thereafter, he displayed symptoms of poisoning, which steadily became worse, and he died about a month later.

These cases and others illustrate the long latent period for mercury poisoning - on the order of months between the exposure and the onset of symptoms. The above-mentioned victims received severely toxic, even fatal, doses of mercury without being aware that exposure was taking place. When the first signs and symptoms of poisoning appeared, irreversible brain damage had already occurred.

Our recent experience also leads us to warn of hazards involved with shipping mercury compounds. We urge that commercial suppliers be required to take more precautions in shipping orders. The present sample - in liquid form in a sealed glass container - was sent from a supplier in a cardboard box filled with small pieces of Styrofoam-type material. If the package had been smashed during shipping, people in the vicinity might have been severely poisoned.

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