Drinking water arsenic in northern Chile: high cancer risks 40 years after exposure cessation
Menée en Chine auprès de 538 cas et de 640 témoins, cette étude analyse l'association entre une consommation d'eau potable contaminée par de hautes concentrations en arsenic durant la période 1958-1970 et le risque de cancer du poumon et de la vessie, 40 ans après la cessation de cette exposition
Background: Millions of people worldwide are exposed to arsenic-contaminated water. In the largest city in northern Chile (Antofagasta) >250,000 people were exposed to high arsenic drinking water concentrations from 1958 until 1970 when a water treatment plant was installed. Because of its unique geology, limited water sources, and good historical records, lifetime exposure and long-term latency patterns can be assessed in this area with better accuracy than in other arsenic-exposed areas worldwide. Methods: We performed a population-based case-control study in northern Chile from October 2007 to December 2010 involving 232 lung and 306 bladder cancer cases and 640 age- and gender-matched controls, with detailed information on past exposure and potential confounders, including smoking and occupation. Results: Bladder cancer odds ratios for quartiles of average arsenic concentrations in water before 1971 (<11, 11-90, 91-335, and >335 µg/L) were 1.00, 1.36 (95% confidence interval, 0.78 to 2.37), 3.87 (2.25 to 6.64), and 6.50 (3.69 to 11.43), respectively. Corresponding lung cancer odds ratios were 1.00, 1.27 (0.81 to 1.98), 2.00 (1.24 to 3.24), and 4.32 (2.60 to 7.17). Bladder and lung cancer odds ratios in those highly exposed in Antofagasta during 1958-70 but not thereafter were 6.88 (3.84 to 12.32) and 4.35 (2.57 to 7.36), respectively. Conclusions and Impact: The lung and bladder cancer risks that we found up to 40 years after high exposures have ended are very high, and suggest that prevention, treatment, and other mortality reduction efforts in arsenic-exposed countries will be needed for decades after exposure cessation.