Positive Patch Test for Mercury Possibly from Exposure to Amalgam

ABSTRACT

Objectives: Mercury allergy is a serious health problem. We investigated the relationship between positive patch test for mercury and sources of mercury exposure, indicated by concentrations in biological samples from healthy medical students. Methods: Patch tests for mercury (Hg-PT) were performed on 580 students. For a group of 55 students with a positive Hg-PT result (Hg-PT(+)) and a reference group of 79 students with a negative Hg-PT result (Hg-PT(−)), mercury concentrations in urine (Hg-u) and hair (Hg-h) were measured. In our search for environmental indicators of mercury exposure, the level of fish intake and mercurochrome usage were determined using a self-administered questionnaire. The oral cavity was investigated and the numbers of decayed teeth filled with amalgam (NA) were counted by dentists. Results: For the male Hg-PT(+) group, Hg-u and Hg-h were higher than those of a male reference Hg-PT(−) group; Hg-u values obtained in the early morning and after supper were significantly different. Multiple regression analysis with Hg-u as the objective variable among all students showed that increases in the level of fish intake, mercurochrome usage, and the NA independently increased Hg-u measured in the early morning for both gender groups. NA significantly affected Hg-u. Conclusions: We showed that a higher NA was related to a higher Hg-u measured in the early morning. Therefore, exposure to amalgam may increase Hg-u. It was suggested that Hg-PT(+) might be related to a high Hg-u, and possibly to a high NA.