Integrated indexes of occupational exposure as predictors of kidney dysfunction.

The aim of the study was to evaluate the dose-effect and dose-response relationships between the integrated indexes Cd-A x t (mg/m3 x years of exposure) and Cd-B x t (microg/l x years of exposure), and the increase in retinol binding protein excretion in urine (RBP-U) and beta2-microglobulin concentration in serum (beta2M-S). The study was carried out in the nickel-cadmium battery factory in 1998-1999. Exposure to cadmium was formerly very high. The study group consisted of 116 persons for whom the results of determinations of Cd-B were available during two former observation periods (1983 and 1986-1988). The mean age of the group was 49 years and the mean period of exposure was 17 years. The dose-effect relationship between Cd-B x t and RBP-U or beta2M-S was much better (r = 0.642 and 0.513) than between Cd-A x t and RBP-U or beta2M-S (r = 0.173 and 0.127). There was also correlation between Cd-U (microg/g creatinine), measured in 1998-1999, and RBP-U or beta2M-S (r = 0.343 and 0.198). Urinary cadmium should, however, be used with caution as a dose estimate because its excretion may increase as a result of renal damage. According to the dose-response relationship, an increase in RBP excretion above 300 microg/g creatinine can be expected in 10% of subjects at the integrated exposure index (Cd-B x t) of about 450 microg/l x years, and an increase in beta2M-S above the accepted cut-off point of 2.4 mg/l can be expected in 10 % of subjects at Cd-B x t of about 190 microg/l x years. The data obtained confirmed the validity of the recommended at present health-based limit for occupational exposure of 5 microg/l of blood, as well as the superiority of the biological monitoring of exposure to cadmium over the environmental monitoring.