Death rates from bladder and lung cancer are still high in a region of northern Chile, even decades after residents drank water containing high levels of arsenic.
According to the authors of a new study, there is delay in health effects, given mortality risks remained elevated years after exposure to high levels of arsenic. “The impact of this environmental health risk on cancer mortality in a human population is without precedent,” University of California, Berkley, researcher Allan Smith, M.D., Ph.D., was quoted as saying.
Previous studies have shown arsenic causes lung, bladder and skin cancers. Other research has also shown a link between arsenic and kidney and liver cancers. The maximum allowance for arsenic levels in community water systems in the much of the world, including the United States, was once 50 micrograms per liter. The World Health Organization recently issued guidelines lowering the maximum containment level for public water supplies to 10 micrograms per liter.
The arsenic levels in the investigated region of Chile contained about 90 micrograms per liter until 1958, according to background information included in the study. Chilean government officials then sought out safer alternatives for their water supply from nearby rivers, which unfortunately contained even higher levels of arsenic. From 1958 to 1970, the region consumed water averaging 870 micrograms of arsenic per liter, nearly 90 times higher than today’s WHO standard. Treated seawater has recently been added to the region, reducing arsenic levels to about 10 micrograms per liter.
The study from the University of California, Berkley, was the first to reveal the latency period between the onset and reductions in exposure and the consequent rise and fall in cancer rates by studying data from lung and bladder cancer deaths from 1950 to 2000 and comparing it to a similar region in Chile that had not been exposed to high levels of arsenic. Researchers found the death rates from cancer increased in 1968, 10 years after the area’s rise in arsenic levels. Between 1992 and 1994, the combined lung and bladder cancer mortality rates were almost three-times higher than their counterparts from the other region, even 20 years after arsenic levels in the water sources dropped.
Study authors note the effects of drinking arsenic take years to decades to disappear. “There isn’t a treatment, although it is clear that there is evidence that arsenic may act jointly with smoking, so certainly that’s added reason to stop smoking. And also a good diet may assist [in reversing effects], but the main thing is to stop the exposure,” Dr. Smith told Ivanhoe.
SOURCE: Ivanhoe interview with Allan Smith, M.D., Ph.D., Journal of the National Cancer Institute, published online June 12, 2007
