Arsenic is an extremely potent carcinogen and toxic to vital organs such as the liver, skin, kidney, and cardiovascular system. A common pathway of human exposure is through drinking water. Previous studies that assessed the long-term exposure to arsenic in drinking water have lacked resolution and rely too heavily on retrospective analysis. However, a 10-year study in Bangladesh has been released recently, and promises to be the definitive study to determine the long-term effects of arsenic exposure.
Arsenic is an extremely potent carcinogen and toxic to vital organs such as the liver, skin, kidney, and cardiovascular system. A common pathway of human exposure is through drinking water. Previous studies that assessed the long-term exposure to arsenic in drinking water have lacked resolution and rely too heavily on retrospective analysis. However, a 10-year study in Bangladesh has been released recently, and promises to be the definitive study to determine the long-term effects of arsenic exposure.
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The study was conducted by an international team from Chicago, New York, and Bangladesh. The title of the study is "The Health Effects of Arsenic Longitudinal Study" or HEALS. It was led by Habibul Ahsan, Director of the Center for Cancer Epidemiology and Prevention at the University of Chicago Medical Center. It is the first study to accurately measure the relationship between individual arsenic exposure and its associated mortality risk. Arsenic levels in the drinking water were monitored, as were biennial urine samples.
The results of the study are quite interesting. Of the 12,000 Bangladeshis who took part, more than twenty percent of deaths were attributable to arsenic in the drinking water. For the 25 people exposed to the greatest levels, mortality risk grew to nearly 70 percent. For those exposed to moderate levels, the study noted an increase in deaths from chronic diseases.
The HEALS project was conducted on a massive scale. Twelve thousand subjects had to be recruited and tested for baseline arsenic levels in their drinking water and in their urine at the outset of the study. Then, they had to undergo follow-up tests every two years thereafter. Over one hundred staff members traversed the Bangladeshi countryside by foot, car, or boat to collect samples from the test subjects and measure arsenic levels in local wells.
Millions of these wells were installed in the 1970’s by global health organizations concerned with providing clean water to Bangladesh. As many as 77 million people, or half the population, who drink from these wells, have been unwittingly exposed to dangerous levels of arsenic. The World Health Organization (WHO) has called in "the largest mass poisoning of population in history."
"We set up this study to measure health effects based on individual level data so that other factors or biases that may affect our study findings were much less likely," Ahsan said. "This allowed us to examine disease quite reasonably in a more accurate way."
Large portions of Bangladesh's populated areas have incredibly high arsenic levels of up to 400 parts per million! By way of comparison, the USA for the most part contains groundwater with arsenic concentrations at 10 parts per million and lower. There are only a few areas with higher levels, and they are in the more sparsely populated parts of the American West.
Of all participants in the study, one quarter drank water within the WHO-recommended arsenic level of ten parts per million. On the other hand, the upper quartile was exposed to levels 27 times as high! This group was 68 percent more likely to die from arsenic related diseases during the testing period (after controlling for other factors like sex, age, smoking, etc.)
Subjects exposed to more moderate levels had smaller but still elevated risk of mortality. For all exposed to levels greater than the WHO-recommended safe level, 21.4 percent of all deaths, and 23.5 percent of deaths from chronic disease came from arsenic exposure. Also, the study found no reduction in the risk of death for subjects with high baseline arsenic levels that were lowered in subsequent follow-up measurements. Therefore, the effects of long-term arsenic exposure are not reduced even when they are given access to clean drinking water.
Regardless, for those people with high levels of arsenic in their systems, further exposure should be reduced immediately. This is a monumental task for Bangladesh, known to be one of the poorest countries on Earth. It means replacing the everyday drinking water for at least fifty million people. If any relief is possible, it will come from government action or international assistance.
For more information: http://thorax.bmj.com/content/65/6/528.abstract
