Residents of Bangladesh exposed to well water with arsenic concentrations as low as 10µg/L are at potentially increased risk of death, finds an Article published Online First in The Lancet. An estimated 21% of deaths from all causes and 24% of deaths linked to chronic diseases could be attributed to drinking arsenic-contaminated well water at concentrations greater than 10µg/L. These findings have important public health implications for other populations that have low-level arsenic exposure through drinking water.
Long-term arsenic exposure has been linked with a higher risk of cancers of the liver, kidney, bladder, and skin, heart disease, and other serious health problems. Drinking water contaminated with arsenic is a significant public health problem in at least 70 countries. Since the 1970s, when aid organisations dug millions of hand-pumped wells to provide disease-free water, an estimated 35 million people in Bangladesh have been drinking well water contaminated with arsenic. WHO has referred to the situation in Bangladesh as "the largest mass poisoning of a population in history."
Up until now, the association between arsenic exposure and death has not been prospectively investigated, with exposure measured at an individual level. Additionally, previous estimates of the health effects associated with exposure have largely been based on research in populations exposed to high concentrations of arsenic.
Therefore, Habibul Ahsan from the University of Chicago, USA, and international colleagues established the Health Effects of Arsenic Longitudinal Study (HEALS) to examine the association between a wide range of concentrations of arsenic exposure through drinking water and a variety of health outcomes. The researchers examined death from all causes in 11 746 Bangladeshi adults.
Information on arsenic exposure was calculated at an individual level based on arsenic concentrations in the well water and repeated urine samples collected at the start of the study and every two years during follow-up. A verbal autopsy questionnaire was used to determine cause of death.
Over an average of 6 years of follow-up there were 407 deaths. Findings showed an increasing risk of death at increasing concentrations of arsenic in the well water. Compared to residents with the lowest levels of arsenic exposure (0.1-10.0 µg/L), residents exposed to 10.1.0µg/L of arsenic in drinking water had a 1.34 times increased risk of death and those with the highest level of exposure (150.1�.0µg/L) had a 1.68 times increased risk of death, after adjusting for various factors including age, sex, smoking status, and education. Results were similar for daily arsenic dose and total arsenic concentration in urine.
The authors also noted that after long-term exposure, decreasing exposure for a short amount of time did not lower an individual's risk of death.
The results of this study, say the authors, "have important public health implications for arsenic in drinking water. Roughly 24% of the people in the cohort had arsenic concentrations in well water less then 10µg/L and 45% had less then 50 µg/L, which makes exposure levels similar to other populations that have low-level arsenic exposure."
They conclude by calling for urgent solutions and resources to mitigate the resulting health effects of this public health disaster for millions of Bangladeshis.
In a Comment, Professor Margaret Karagas from the Dartmouth Medical School, New Hampshire, USA, says: "The beauty of the HEALS cohort is that it includes concentrations at the lower end of the dose-response curve and concentrations at the high end at which known health effects occur. Such data are rarely available, yet they are important for establishing rational guidelines."
Professor Habibul Ahsan, University of Chicago, Illinois, USA. T) +1 773 834 9956 E) habib@uchicago.edu
Professor Margaret Karagas, Dartmouth Medical School, Hanover, New Hampshire, USA.T) +1 603 653 9010 E) Margaret.Karagas@Dartmouth.edu
For full Article and Comment see: http://press.thelancet.com/heals.pdf
Journal
The Lancet