Mortality and cancer incidence among a population previously exposed to environmental cadmium

Objectives: This paper evaluates the associations of previous exposure to e nvironmental cadmium (Cd) and renal function with total mortality and cance r incidence. Methods: The study population comprised 275 residents (aged 40 -92 years at baseline) in a Cd-polluted area located on Tsushima Island, Na gasaki, Japan. In the study area, the dietary intake of Cd decreased becaus e the soil of the Cd-polluted rice fields was replaced with new soil betwee n 1980 and 1983. The mortality rate from 1982 to 1997 and cancer incidence from 1985 to 1996 were investigated. Standardized mortality and incidence r atios (SMR and SIR) were calculated by using regional reference rates. The associations of renal function and urinary Cd levels with total mortality a nd cancer incidence were evaluated with Cox regression models. Results: The SMR for all subjects, and those with a urinary beta (2)-microglobulin (U-b eta M-2) concentration greater than or equal to1,000 mug/g creatinine (Cr) and < 1,000 mug/g Cr was estimated at 90 [95% confidence interval (CT) 73-1 09], 138 (95% CI 101-183) and 66 (95% CI 49-87), respectively. After adjust ment for age and other potential confounders, in men, serum beta M-2 (S-bet a M-2) (greater than or equal to2.3 mg/l) and in women, serum Cr (greater t han or equal to1.2 mg/100 ml), relative clearance of beta M-2 (greater than or equal to1%) and U-beta M-2 (greater than or equal to1,000 mug/g Cr), we re associated with a significantly increased risk of mortality, with hazard ratios exceeding 2.0. After further adjustment for log(U-beta M-2), the ra te ratio of deaths associated with: in men, increased S-beta M-2 was 2.53 ( 95% CI 0.97-6.65) and, in women, increased serum Cr (S-Cr) concentrations w as 2.75 (95% CI 1.24-6.14). Urinary Cd concentrations (greater than or equa l to 10 mug/g Cr) were not significantly associated with mortality. The ove rall SIR of all malignant neoplasms was 71 (95% CI 44-107). Conclusions: Th ese findings suggest that renal tubule dysfunction and a reduced glomerular filtration rate are predictors of mortality among persons previously expos ed to environmental Cd. However, the results also suggest that overall mort ality rates in Cd-polluted areas are not necessarily increased, because of the low mortality among those with no, or only slight, signs of low-molecul ar weight proteinuria. Overall cancer incidence may not be increased among residents in Cd-polluted areas.