Environmental Factor, July 2010, National Institute of Environmental Health Sciences
Arsenic Exposure Shown to Increase Risk of Death
By Rebecca Wilson
According to a new NIEHS-funded study, 35-77 million Bangladeshis may face a higher risk of death from chronic exposure to arsenic in their drinking water. Superfund Research Program researchers at Columbia University, led by Habibul Ahsan, M.D. (http://www.mailman.columbia.edu/our-faculty/profile?uni=ha37) , published this finding June 19 online in The Lancet. They report that in their six-year cohort study nearly 21 percent of deaths from all causes and 24 percent of deaths linked to chronic disease could be attributed in part to drinking arsenic-contaminated water. A unique aspect of their study (http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2810%2960481-3/fulltext) is that arsenic exposure has been followed at the level of the individual in nearly 12,000 adults (see CNN video).
In the prospective "Health Effects of Arsenic Longitudinal Study" (HEALS), trained physicians unaware of the levels of exposure conducted in-person interviews and clinical assessments of 11,746 adults from Araihazar, Bangladesh. Roughly 24 percent of the participants had arsenic concentrations in well water less than 10 micrograms per liter (µg/L), the World Health Organization recommended standard, and 45 percent had less than 50µg/L, the Bangladeshi standard. These exposure levels are similar to other populations around the world that have low levels of arsenic in their water.
Following recruitment and baseline assessments, the physicians followed up biennially with participants for six years. During the study period, there were 407 deaths, the causes of which were identified using a validated verbal autopsy questionnaire given to family or neighbors. The findings showed an increased risk of death with increasing concentrations of arsenic in the well water.
The mortality rate also increased with increasing arsenic consumption over time, regardless of the concentration of arsenic in the well water, "indicating an increasing risk rather than a threshold effect," the authors wrote. The increased risk seems to persist even after reduction of exposure for up to four years.
The drinking water contamination problem began in Bangladesh in the 1970s, when aid organizations dug millions of hand-pump wells in an effort to provide clean, pathogen-free drinking water to the residents. What they didn't know at the time is that the water was contaminated with elevated levels of naturally-occurring arsenic (see BBC story (http://news.bbc.co.uk/2/hi/south_asia/252308.stm) ). According to UNICEF (http://www.unicef.org/bangladesh/Arsenic_Mitigation_in_Bangladesh.pdf) , the arsenic wasn't detected until the early 1990's. The World Health Organization calls this situation "the largest mass poisoning of a population in history."
According to Ahsan, it is important to note that the Columbia University Superfund Research Program (CUSRP) (http://tools.niehs.nih.gov/srp/programs/Program_detail.cfm?Project_ID=P42ES10349) has also made great strides in reducing arsenic exposure in their study population. The cohort has recently been expanded to 20,000 for examining rarer health outcomes. Also, one of Ahsan's newly established projects is to evaluate nutritional interventions to minimize health impacts of arsenic.
In a talk last year at Duke University, CUSRP Director Joseph Graziano, Ph.D., a coauthor on this study, described some of the program's remediation efforts in the region (see story (http://www.niehs.nih.gov/news/newsletter/2009/march/ghs.cfm)).
Citation: Argos M, Kalra T, Rathouz PJ, Chen Y, Pierce B, Parvez F, et al. (http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2810%2960481-3/fulltext) 2010. Arsenic exposure from drinking water, and all-cause and chronic-disease mortalities in Bangladesh (HEALS): a prospective cohort study. Lancet. Epub ahead of print. doi:10.1016/S0140-6736(10)60481-3. [Summary (http://www.niehs.nih.gov/news/newsletter/2010/july/science-extramural.cfm#one)]
(Rebecca Wilson is an environmental health information specialist for MDB, Inc., a contractor for the NIEHS Superfund Research Program and Worker Education and Training Program.)