Incidence of renal stones among cadmium exposed battery workers

The health effects of occupational exposure to cadmium were studied in a group of 902 workers employed for at least one year in a Swedish battery factory between 1931 and 1982. Data on air cadmium concentrations for different periods were combined with company employment records to obtain individual cumulative exposure estimates. A questionnaire including questions on the occurrence of kidney stones was sent to all 601 living workers and to the next of kin of 267 of the deceased workers. The response rate was 88%. 73 workers reported renal calculi that appeared after initial employment. A dose-response relation was found between cumulative exposure to cadmium and age standardised cumulative incidence. Incidence rate ratios (IRRs) were then computed for three exposure categories (< 250, 250- < 5000, and 5000 micrograms/m3 x years) standardised for calendar time, age, and smoking with the low exposure group as reference level. The IRRs were 1.0, 1.6 [95% confidence interval (95% CI) 0.7-3.4], and 3.0 (95% CI 1.3-6.8) respectively. beta 2 Microglobulin measurements were available for 33 workers who formed stones; 13 of these workers had tubular proteinuria (beta 2 microglobulin > or = 34 micrograms/mmole creatinine)--that is, a prevalence of 39%. There was also an indication of a steeper dose-response relation among workers with tubular proteinuria.