TUESDAY, June 12, 2007 (HealthDay News) -- Decades after residents of a region in northern Chile were exposed to high levels of arsenic in their drinking water, they still suffer from high lung and bladder cancer death rates, concludes a study by U.S. and Chilean researchers.
The finding indicates a pattern of long-term arsenic-related health effects that hasn't been documented before, said the authors of a study in the June 12 Journal of the National Cancer Institute.
"The results show that the risks of concentrated arsenic exposure are extraordinarily high, and that they last a very long time, both after initial exposure, and after the exposure ends," principal investigator Allan Smith, professor of epidemiology at the University of California, Berkeley, School of Public Health, said in a prepared statement.
From 1958 to 1970, arsenic levels in drinking water in the northern Chilean cities of Antofagasta and Mejillones averaged 870 micrograms per liter, nearly 90 times higher than current World Health Organization and U.S. standards of 10 micrograms per liter. The communities got their water from arsenic-contaminated rivers.
Improvements to the water treatment system that began in 1971, along with other measures, have reduced arsenic levels to about 10 micrograms per liter.
For this study, researchers analyzed data on lung and bladder cancer deaths in this area (Region II) from 1950 to 2000.
They found that those kinds of cancer deaths started to increase in 1968, which was 10 years after the major jump in arsenic levels in drinking water.
Death rates from these two kinds of cancer continued to increase and peaked between 1986 and 1997. Between 1992 and 1994 (more than 20 years after arsenic levels started to decline), the combined death rates for bladder and lung cancer in Region II were 153 per 100,000 men and 50 per 100,000 women -- 2.5 to three times higher than in another region in northern Chile that did not have high levels of arsenic in the drinking water.
"The impact of this environmental health risk on cancer mortality in a human population is without precedent. This study adds to the overall body of evidence of the harmful effects of arsenic," Smith said.
The U.S. Agency for Toxic Substances and Disease Registry has more about arsenic.