Cause-specific mortality and cancer incidence rates in relation to urinary beta2-microglobulin: 23-year follow-up study in a cadmium-polluted area

A longitudinal study was performed to investigate the associations of exposure to environmental cadmium (Cd) with cause-specific mortality and cancer incidence rates. The study population comprised 275 adults living in a Cd-polluted area, Nagasaki Prefecture, Japan. The follow-up period extended from 1982 to 2005 for the analysis of cancer mortality, and from 1985 to 2002 for the analysis of cancer incidence. In the study area, the daily Cd intake from foods had decreased after 1980-1983 because of the restoration of Cd-polluted rice fields. The mortality rate among those with urinary beta2-microglobulin (U-beta2M)>/=1000 microg/g creatinine was significantly higher than that of the Japanese population for death from causes other than cancer, but not for cancers (177 at the 95% confidence interval CI] 94-303). From analysis within the Cd-polluted area, the age-adjusted rate ratio of cancer deaths associated with increased U-beta2M was 2.58 (95% CI 1.25-5.36). The incidence rate of cancer among those with U-beta2M>/=1000 microg/g creatinine was 1.38 (95% CI 0.69-2.47) times that of the regional reference rate. Within the Cd-polluted area, the age-adjusted rate ratio of developing cancer associated with high U-beta2M was 1.79 (95% CI 0.84-3.82). In summary, there was a significant association between U-beta2M excretion and cancer mortality. However, there was neither a significantly increased standardized incidence ratio of cancer, nor significant relationship between U-beta2M and cancer incidence rate, though the point estimates were higher than unity. Continued follow-up and investigation of a larger cohort may be required before drawing a conclusion for the association between exposure to environmental Cd and cancer risk.