title: Positive patch test for mercury possibly from exposure to amalgam.
abstract: OBJECTIVE
  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.
authors: Fukui Prefectural Institute of Public Health and Environmental Science, 39-4, Harame-cho, 910-8551, Fukui-city, Fukui, Japan, moritomio@fklab.fukui.fukui.jp.
authors: Tomio
authors: T
authors: Mori
authors: Kazuhiro
authors: K
authors: Sato
authors: Yukinori
authors: Y
authors: Kusaka
authors: Toshiko
authors: T
authors: Ido
authors: Masanobu
authors: M
authors: Kumagiri
authors: Toshiyuki
authors: T
authors: Ogasawara
authors: Kazuo
authors: K
authors: Sano