Factors affecting the amount of mercury in human scalp hair

Hair samples were collected from several socioeconomic and ethnic groups in Japan and from 2 groups (vegetarians vs nonvegetarians) in India. The samples were analyzed for the amount of total mercury and methylmercury. A large amount of mercury in the hair of molybdenum refinery workers who were exposed to mercury vapor was detected. However, the amount of methylmercury in them was almost in the normal range. This suggests that the abnormal amount of mercury found in hair samples can be attributed to the mercurial contamination to which they have been exposed. On the other hand, a large amount of mercury was detected in the hair of Minamata patients and the ratio of methylmercury to total mercury in hair samples from this group was significantly larger than that in mercury workers who had heavy mercury exposure. This is evidence that the Minamata patients absorbed methylmercury by the gastrointestinal route through the ingestion of fish. It is suggested in this report that the amount of fish consumed significantly influences the mercury content in scalp hair, particularly the methylmercury content. Consequently, the actual or potential health hazards, particularly from a low level of alkylmercury contained in marine products caught in a natural environment, urgently require further study. The importance of determining the ratio of methylmercury to the total mercury in biological specimens for an assessment of mercury absorption is also emphasized. This means that the significance of the amount of mercury in hair specimens should not be evaluated merely by the total amount of mercury; determination of the ratio of methylmercury to total mercury is necessary.