Cadmium-Related Mortality and Long-Term Secular Trends in the Cadmium Body Burden of an Environmentally Exposed Population

BACKGROUND Few population studies have reported on the long-term changes in the internal cadmium dose and simultaneously occurring mortality. OBJECTIVE We monitored blood cadmium (BCd), 24-hr urinary cadmium (UCd), and mortality in an environmentally exposed population. METHODS Starting from 1985, we followed BCd (until 2003), UCd (until 1996), and mortality (until 2007) among 476 and 480 subjects, randomly recruited from low- exposure areas (LEA) and high-exposure areas (HEA). The last cadmium-producing plant in the HEA closed in 2002. RESULTS From 1985-1989 to 1991-1996, BCd decreased by 40.3% and 18.9% in the LEA and HEA, respectively (p < 0.0001 for between-area difference). From 1991-1996 until 2001-2003, BCd remained unchanged in the HEA (+ 1.8%) and increased by 19.7% in the LEA (p < 0.0001). Over the entire follow-up period, the annual decrease in BCd averaged 2.7% in the LEA (n = 258) and 1.8% in the HEA (n = 203). From 1985-1989 to 1991-1996, UCd fell by 12.9% in the LEA and by 16.6% in the HEA (p = 0.22), with mean annual decreases of 2.7% (n = 366) and 3.4% (n = 364). Over 20.3 years (median), 206 deaths (21.5%) occurred. At baseline, BCd (14.6 vs. 10.2 nmol/L) and UCd (14.1 vs. 8.6 nmol/24-hr) were higher in deaths than in survivors. The risks (p < or = 0.04) associated with a doubling of baseline UCd were 20% and 44% for total and noncardiovascular mortality, and 25% and 33% for a doubling of BCd. CONCLUSIONS Even if zinc-cadmium smelters close, historical environmental contamination remains a persistent source of exposure. Environmental exposure to cadmium increases total and noncardiovascular mortality in a continuous fashion without threshold.