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Cancer cluster in Chile linked to arsenic contamination

2012; Elsevier BV; Volume: 379; Issue: 9816 Linguagem: Inglês

10.1016/s0140-6736(12)60253-0

1474-547X

Barbara Fraser,

Arsenic contamination and mitigation

Clusters of bladder cancer in north Chile have been linked to arsenic contamination in the 1950s, highlighting the need of increased vigilance and screening, say researchers. Barbara Fraser reports. What began as a straightforward exercise in mapping urological diseases in Chile took an unexpected turn when urology specialist Fernando Coz and a group of residents noticed a cluster of bladder cancer cases on the north coast. “The number of hospital discharges for bladder cancer in the Antofagasta region looked like an error, because it was four or five times the rate in any other region of the country”, said Coz, a urology professor at the University of the Andes in Santiago and chief of urology services at Chile's Military Hospital. Puzzled, the researchers looked more closely and found that Antofagasta also had a higher bladder-cancer mortality rate than any other part of the country. And the deaths came at an earlier age than in the rest of Chile. But it was when they noticed an accompanying uptick in lung cancer rate that the investigators zeroed in on the cause. “Those are two related pathologies that are known to be induced by arsenic poisoning”, Coz told The Lancet. The catch: most of the arsenic was removed from Antofagasta's water supply four decades ago, and no one was watching for possible consequences a generation later. The increase in bladder cancer that he and his colleagues found highlights the importance of public awareness and screening in places known to have high arsenic levels, Coz said. Arsenic in water on Chile's volcanic north coast has a long history—the amount detected in the hair of 7000-year-old mummies discovered near the northern city of Arica has led archeologists to wonder if arsenic poisoning, which is linked to miscarriages, could be responsible for the number of mummified fetuses found in the tombs. In Antofagasta, exposure was severe but of limited duration. Until the mid-1900s, the sparsely populated region drew drinking water from an arsenic-free river. When the population surged with a mining boom in the 1950s, the water system was expanded to include two other rivers. Arsenic concentrations increased tenfold, and residents were exposed to levels as much as 17 times the WHO recommendation. A treatment plant built in 1971 brought arsenic concentrations down sharply, although it took two more decades for them to reach levels recommended by WHO. Meanwhile, people who had grown up in Antofagasta, especially in the 1950s and 1960s, were unknowingly at higher risk for cancer. “Today, the water in the Antofagasta region is perfectly clean”, Coz said. “But with arsenic, the harm is to children, more than adults, particularly when the child is in utero.” People who were exposed as children in Antofagasta are now at the age where cancers are appearing, often 10 years earlier than would normally be expected, he said. The study found a steady increase in bladder-cancer mortality rates over the past 60 years, peaking for men at 26·7 per 100 000 in 1991 and for women at 18·7 per 100 000 in 2001. Between 1985 and 2000, the mortality rate for men in Antofagasta was 2·9 to 5·8 times the average for the rest of Chile. Since 2006, it has been between 2·8 and 3·3 times the national average. The mean age at death from bladder cancer was 69·6 years in the affected region, compared with 73·7 years in the rest of the country. Antofagasta is not the only place in Latin America that could have a latent risk from arsenic, which occurs naturally in groundwater, especially in volcanic areas. A 2006 survey by the Pan American Health Organization identified possible hot spots in northern Argentina, in a volcanic belt in Mexico, and near La Paz, Bolivia, and Ilo, Peru, as well as in industrial areas near copper smelters. Coz would like his study—due to be published in the March issue of the Journal of Urology—to be a wake-up call to health authorities in Chile and other potential trouble spots. He also hopes it will spur a nationwide public-awareness campaign to alert people who were born in Antofagasta or lived there as children and encourage early cancer screening for them. Meanwhile, Coz has his eye on the next puzzle—Chile's testicular cancer rate is one of the highest in the world, according to WHO. Mapping has not shown clusters, and he is unsure of the cause, although he would like to rule out misreporting on death certificates. Even Coz has been surprised by the scope of his simple mapping exercise. “It was an invention of mine that looked like it would be practical” by drawing comparisons among different regions of the country, he said. “But these surprises appear, leading us to investigate further.”