Background: Arsenic in drinking water is associated with kidney cancer. Beginning in 1958, a region of Chile experienced a rapid onset of high arsenic exposure in drinking water, followed by sharp declines when water treatment plants were installed in 1971.
Methods: For the years 1950–1970, we obtained mortality data from death certificates for an exposed region and an unexposed region in Chile. We obtained computerized mortality data for all of Chile for 1971–2000.
Results: Kidney cancer risks for the exposed region compared with the unexposed started to increase about 10 years after high arsenic exposures began in 1958. The peak kidney cancer mortality rate ratio (RR) was 3.4 (95% confidence interval = 2.2–5.1) for men in 1981–1985, with subsequent declines to 1.6 (1.2–2.1) by 1996–2000. Mortality RRs among women were 2.9 (1.8–4.7) in 1981–1985 but remained high longer than for men, increasing further to a RR of 4.4 (3.0–6.4) in 1991–1995. Early-life exposure resulted in an increased RR of 7.1 (3.1–14) for young adults aged 30–39 years, born just before or during the high exposure period.
Conclusions: This study shows a latency pattern of increased mortality from kidney cancer, continuing for at least 25 years after the high exposures began to decline. Early life exposure resulted in markedly higher kidney cancer mortality in young adults.