Arsenic exposure appears to continue causing lung and bladder cancer deaths years after exposure ends, according to a study published online June 12 in the Journal of the National Cancer Institute.
Arsenic is a known cause of lung and bladder cancer, but researchers don?t yet know how long cancer risk remains elevated after arsenic exposure. The drinking water in a region of northern Chile became contaminated with very high amounts of arsenic beginning in 1958. In the 1970s, construction of water treatment plants in the region led to a decline in arsenic concentration. This sudden rise and fall of arsenic levels gave researchers the opportunity to investigate the period between first and last exposure to high levels of arsenic and subsequent mortality due arsenic-related cancers, such as bladder and lung cancer.
Guillermo Marshall, Ph.D., of Pontificia Universidad Cat?lica de Chile in Santiago and colleagues including collaborators from the University of California, Berkeley, investigated bladder and lung cancer death rates in the region between 1950 and 2000 and compared them with data from a similar region farther south, where the water was not contaminated.
Lung and bladder cancer mortality rates in the area with arsenic-contaminated drinking water began to rise about 10 years after arsenic levels rose. They then continued to climb, peaking between 10 and 20 years after the arsenic levels dropped. At the peak, lung cancer deaths among men and women in the contaminated region were about three times higher than in the control region, while bladder cancer deaths were six times higher in men and 14 times higher in women. The lag time between exposure to a carcinogen and the peak of cancer deaths is usually difficult to determine, but the size of the study and the record of arsenic exposure aided the researchers.
?The impact of arsenic in drinking water on this large population is without precedent for environmental causes of human cancer, and it points to the public health priority of ensuring that arsenic concentrations in drinking water are controlled worldwide,? the authors write.
In an accompanying editorial, Jay H. Lubin, Ph.D., of the National Cancer Institute in Bethesda, Md., and colleagues note that there are many health-related consequences associated with arsenic exposure and that millions of people in both developed and developing countries rely on water with arsenic levels that exceed the recommended limit of 10 ?g/L.
?With large numbers of people potentially exposed to arsenic in drinking water above 10 ?g/L, the full scope of the public health consequences of arsenic in drinking water is not yet clear,? the authors write.