A 1982-1992 SURVEILLANCE PROGRAM ON DANISH POTTERY PAINTERS - BIOLOGICAL LEVELS AND HEALTH-EFFECTS FOLLOOWING EXPOSURE TO SOLUBLE OR INSOLUBLE COBALT COMPOUNDS IN COBALT BLUE DYES

This paper provides a short overview of cobalt-related diseases with p articular reference to the potential carcinogenicity of cobalt compoun ds, and a review of a 10-year surveillance programme on plate painters exposed to cobalt in two Danish porcelain factories. Clinical experie nce and epidemiological studies have demonstrated that cobalt exposure may lead to severely impaired lung function, i.e. hard metal lung dis ease and occupational cobalt-related asthma, contact dermatitis and ca rdiovascular effects. However, the evidence for the carcinogenicity of cobalt and cobalt compounds is considered inadequate (IARC, 1991). Mo st frequently, exposure to cobalt occurs simultaneously with exposure to other elements known to pose a health risk, (e.g. nickel, arsenic, chromium, tungsten). The importance of cobalt as sole causal agent in hard metal long diseases, cardiomyopathy and cancer are still a matter of controversy. In the two Danish porcelain factories, cobalt blue un derglaze dyes have been used since 1888. In contrast to the exposure e xperience of hard metal factories, the exposure of plate painters occu rs with only low trace levels of other potentially harmful compounds s uch as the carcinogenic metals nickel, arsenic and chromium. Consequen tly, the nearly-pure cobalt exposure makes the plate painters an attra ctive group for studies on the health effects of cobalt. During the pe riod 1982-1992 the surveillance programme showed a profound reduction in the urine level of cobalt (Co-U) from 100-fold to 1-fold above the median level of the unexposed control subjects. In the same period, th e airborne cobalt exposure declined from 1356 nmol/m3 to 454 nmol/m3, the Danish occupational exposure limit being 845 nmol/m3. In 1982, whe n the cobalt exposure was above the occupational exposure limit, the p late painters showed a chronic impaired lung function. The obstructive effects may bc similar to some of the effects observed in hard metal workers. In 1988, a study on the effect of cobalt exposure at low leve ls revealed no inhibitory effects on thyroid function, but the ratio b etween T4 and T3 increased, indicating that low cobalt exposure may ha ve an impact on the metabolism of thyroid hormones. Parallel studies w ere conducted on the metabolism and excretion of cobalt. The gastroint estinal uptake of soluble CoCl was considerably higher than the uptake of insoluble cobalt(II) oxide. In addition, it was demonstrated that ingestion of controlled amounts of the soluble cobalt compound resulte d in significantly higher concentrations of cobalt in urine and blood (Co-B) from females compared with males (P < 0.01). Future studies wil l involve epidemiology and genotoxicity to evaluate the previous and p resent cancer risk, and detailed process-related exposure assessment s tudies to select the methods most reliable for surveillance of low-dos e cobalt exposure.