Absence of adverse effect on thyroid function and red blood cells in a population of workers exposed to cobalt compounds.

Context: Hypothyroidism has been observed in the fifties and sixties as an undesirable side-effect of cobalt therapy used for its erythropoietic properties in the treatment of anemia.

Objective: This study aims at evaluating the possible impact of both cumulative (long-term) and recent occupational exposure to cobalt on thyroid function and red blood cells.

Methods And Setting: A cross-sectional survey was conducted from February 2008 to August 2009 in a population of 249 male workers from a cobalt production department in the North of Belgium. The possible effect of cobalt exposure on thyroid and red blood cells was investigated through multiple regression analyses.

Results: Blood cobalt ranged from undetectable to 3.20 μg/100ml (median 0.10); urinary cobalt from 0.30 to 204.30 μg/g(creat) (median 3.90) and long-term exposure to cobalt ranged from 0.15 to 6990.46 μg/g(creat) · years (median 106.09). No effect of cobalt exposure on thyroid or red blood cell parameters was observed at these levels of exposure.

Conclusion: The results support the absence of effects on the thyroid and red blood cells when occupational exposure to cobalt is kept below the recommended biological limit of occupational exposure (15 μg Co/g(creat) in urine).