The history of occupational medicine.

The origin of occupational medicine can be traced to the era of Hippocrates. Many scholars have contributed to the development of this medical specialty, and over the years much has been learned about the relationship of health, disease, and occupation. Presented in this article is a brief sketch of the development of occupational medicine from its inception to the present.

Mercury exposure in chloralkali plants.

The employees of two chloralkali plants were studied to correlate the signs and symptoms of mercury toxicity with levels of exposure. For purposes of comparison, the workers were divided into three groups. These groups were selected on the basis of hours worked in the mercury cell room or in other areas of mercury exposure. The population of the first plant was studied from 1957-1978, and preliminary findings were published in 1964. The second plant's population was studied for 3.5 years beginning in 1976. Time-weighted average exposure levels to mercury vapor in the high exposure group generally ranged between 0.05 to 0.10 mg/m3. No significant differences in the frequency of objective or subjective findings were noted among the three groups except for a lower post exposure systolic and post exposure diastolic blood pressure in the high exposure group in the second plant's population. There was no correlation of mercury vapor exposure with subjective or objective weight loss.

Microenvironmental exposure to mercury vapor.

Work area and breathing zone samples were collected in a factory utilizing metallic mercury and analyzed for mercury vapor content. Breathing zone samples averaged several fold higher in concentration than concurrent area samples, reflecting a "microenvironmental" exposure to mercury vapor, presumably from contaminated clothing and hands. Blood and corrected total urine mercury values correlated well with the average microenvironmental exposure level for each worker. Measurements of unbound mercury in urine samples were sensitive at picking up minimal exposures. Excessive amounts of unbound mercury were not found in the urine, even with wide day-to-day swings in microenvironmental mercury vapor levels, suggesting that the human body can adapt to a chronic, moderate exposure to mercury vapor.

Methylmercury in the environment: a review of current understanding.

The danger of methylmercury poisoning appears to be slight when the environment is not directly contaminated with methylmercury. Sediments rapidly bind mercury and decrease its availability to aquatic organisms. Sediments further have a greater propensity to demethylate than to methylate mercury. In noncontaminated aquatic ecosystems, the concentrations of methylmercury and inorganic mercury are many times lower than those that have been found to cause toxicity, even in the most sensitive organisms. Methylmercury bound to protein is comparatively less toxic than methylmercury salts, and selenium present in this protein appear to be one of the major detoxifying agents for methylmercury. This is particularly important in seafood, where there is an excess of selenium compared to methylmercury.