Longitudinal study of workers exposed to mercury vapour at low concentrations: time course of inorganic and organic mercury concentrations in urine, blood, and hair.

Seven Japanese female workers exposed to mercury vapour at a concentration of < 0.02 mg Hg/m3 (8 h/day, 44 h/week) were examined for inorganic (I-Hg) and organic (O-Hg) mercury concentrations in urine, blood, and hair after 0, 4, 8, 17, and 23 months of exposure. Both I-Hg and O-Hg concentrations in urine and hair did not increase significantly even after 23 months of exposure. The concentration of I-Hg and O-Hg in plasma and O-Hg in erythrocytes, however, increased significantly after four months of exposure, and the high concentrations were maintained until the end of the study (23 months of exposure). Absence of a significant increase in the concentration of O-Hg in hair indicates that changes in concentrations of I-Hg and O-Hg in blood could be caused by the occupational exposure to mercury vapour. These results show clearly that mercury concentration in blood indicates the uptake of mercury compared with data from before employment with mercury. Even after 23 months of exposure to mercury vapour, however, urinary mercury concentration was not affected.