Measuring the mercury burden in dentists

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Measuring the mercury burden in dentists

Regular monitoring of all hazardous materials is an accepted part of working practice under the Control of Substances Hazardous to Health Regulations (COSHH). In the absence of overt signs and symptoms of mercury toxicity in dental staff, a biochemical test which assesses the degree of exposure is required.

Since tissue sampling is obviously not possible, and remote detection by, for example, x-ray fluorescence is not necessarily available, analysts are restricted to a limited range of biological samples. Mercury levels in the blood do reflect the amount absorbed; however, the metal is quite rapidly cleared into the tissues (the half-life is 3 days) and one sample may not be representative of periodic exposure. Hair and nail tissue are quite good indicators of exposure to the organic forms of mercury such as methyl and ethyl mercury, but do not accumulate inorganic mercury sufficiently to form the basis of a simple and accurate analytical method . Mercury is however excreted in the urine in amounts which accurately mirror the total body burden; the long half-life in the body tissues (90 days) effectively smoothes out

differences in day-to-day exposure.

Air sampling methodsMeasurement of the concentration of mercury vapour in the air of dental practices has been carried out in several surveys published in the literature. This system has limited use in potentially exposing a health risk to their staff through elevated mercury vapour levels. While it can be useful in relating the practice exposure risk to the theoretical time-limited value (TLV), the method excludes mercury absorbed via the skin and by inhalation of aerosol material by the dentist; two major routes of absorption. For those practices where personnel are found to have a high mercury burden, air sampling can help identify the source of the contamination. Clearly, though, the ideal situation is to prevent contamination with mercury in

the first place.

Dr. Smita

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