Colour vision loss in workers exposed to elemental mercury vapour.

We evaluated colour vision in 33 workers exposed to elemental mercury (Hg) vapour and in 33 referents matched for sex, age, alcohol consumption and cigarette smoking. The results were expressed as colour confusion index (CCI). In the workers urinary excretion of Hg (HgU) ranged from 28 to 287 micrograms/g creatinine. Subclinical colour vision loss, mainly in the blue-yellow range, was observed in the workers. This effect was related to exposure, as indicated by the correlation between HgU and CCI (r = 0.488, P < 0.01). In the workers whose HgU exceeded 50 micrograms/g creatinine, mean CCI was significantly increased compared to the matched referents. The results suggest that exposure to elemental Hg inducing HgU values exceeding 50 micrograms/g creatinine can induce a dose-related colour vision loss.