Current Hair Mercury Levels in Japanese: Survey in Five Districts

Abstract

To understand the current Japanese hair mercury levels, we planned a survey of hair mercury among the general populations of different regions in Japan. The present paper, as the first report of the survey, summarized the results obtained in five districts, Minamata, Kumamoto, Tottori, Wakayama and Chiba. Hair samples were collected at beauty saloons, barbershops and primary schools in each district with questionnaires on age, sex, amount and species of fish usually consumed, hair-dyed and artificial hair waving “permanent wave.” The total mercury levels of 3686 hair samples collected were analyzed by an oxygen combustion-gold amalgamation method. The geometric mean of the total mercury concentration was significantly higher in males than in females, i.e., 2.55 μg/g and 1.43 μg/g, respectively. The sex difference was also observed on hair samples without artificial waving, i.e., 2.64 μg/g and 1.64 μg/g, respectively. The geometric mean in each district varied from 2.23 to 4.79 μg/g for males and from 1.23 to 2.50 μg/g for females. The average hair mercury levels were highest in Chiba among the five districts both in males and females. A multiple regression analysis revealed a significant correlation of the mercury level with age, sex, amount of daily fish consumption, tuna and bonito as usually consumed fish, artificial waving and Chiba as a residential area. In the laboratory experiment, we found that the treatment of hair samples with a lotion for artificial waving caused a 30%-reduction in the mercury content. Furthermore, longitudinal hair analysis showed a marked difference in the concentration between the hair root and the tip of the hair taken from artificially waved females; higher values were observed at the hair root. These results suggested that artificial waving significantly removes hair mercury and that hair analysis at the hair root should be necessary to estimate an accurate methylmercury exposure for waved persons.