Immunotoxicity of co-exposures to heavy metals: In vitro studies and results from occupational exposure to cadmium, cobalt and lead

Introduction: The influence of cobalt (Co), cadmium (cd) and lead (Pb) on the immune system of occupationally exposed persons was assessed. Methods: 36 persons exposed to Co, Cd and Pb were analyzed. Concentrations of the heavy metals in the air of the working places as well as concentrations in blood and urine of the exposed individuals were measured. Lymphocyte proliferation and in vitro-chromate resistance were determined. Results: In univariate analysis lymphocyte proliferation was correlated to Co in air (Spearman's R=-0.69, p<0.001), Co in urine (R=-0.48, p = 0.003), Pb in blood (R=-0.32, p = 0.058), Cd in air (R=- 0.53, p = 0.001), and Cd in urine (R=-0.40, p=0.021). In vitro-chromate resistance of lymphocytes was correlated to Co in air (Spearman's R=-0.50, p=0.002), Pb in air (R=-0.29, p=0.099), Pb in blood (R=-0.42, p=0.012), Cd in air (R=-0.32, p=0.069), Cd in blood (R=- 0.32, p=0.057), and Cd in urine (R=-0.37, p=0.035). The following potentially influential parameters were included into a multiple logistic regression analysis: Cd in air, in blood and in urine, Co in air and in urine, Pb in air and in blood, Fe in serum, smoking habits, alcohol intake, and age. Only two of them, namely Co in air and Pb in air, were shown to have an explanatory influence. Discussion: Exposures to Co and Pb in concentrations below or close to the current TLV lead to clear effects on lymphocyte proliferation and chromate resistance in exposed individuals. A synergistic effect could be shown. Besides the conventional lymphocyte proliferation assay the newly established chromate resistance assay improves identification of humans exposed to immunotoxic substances.