Biological monitoring of dermal and air exposure to cobalt at a Swedish hard metal production plant: does dermal exposure contribute to uptake?

Background. Occupational exposure to cobalt is well established in hard metal manufacture. Cobalt is known to cause contact allergy, asthma, hard metal lung disease, and lung cancer. The relationship between skin exposure and uptake determined in blood has not been extensively investigated. Objective. To examine whether skin and inhalable air exposure to cobalt contributes to uptake, determined as cobalt in blood, in a hard metal manufacturing factory. Methods. The amount of cobalt on the skin found with an acid wash technique, the air concentrations of inhalable cobalt and cobalt blood concentrations were determined and correlated in exposed workers. Results. We found a significant rank correlation for cobalt concentrations on the skin, in inhalable air, and in blood (0.376-0.498). Multiple linear regression showed significant regression coefficients for cobalt skin exposure and blood (B = 0.01, p < 0.05) and for inhalable cobalt in air and blood (B = 49.1, p < 0.001). According to our model based on data from the regression analyses, a twofold increase in skin exposure levels at different air concentrations caused a 3 - 14% increase in blood levels. Conclusions. Our data suggest that skin exposure to cobalt in the hard metal industry could affect the total uptake at the same order of magnitude as air exposure.