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 concentratio...