A 20-year study in Bangladesh has found that reducing arsenic levels in drinking water was associated with as much as a 50 percent reduction in deaths from heart disease, cancer and other major chronic illnesses. Researchers followed nearly 11,000 adults and reported that participants who switched to safer wells eventually had mortality risks similar to people who were never heavily exposed to arsenic. The findings, published in JAMA, underscore the global health benefits of tackling arsenic contamination in drinking water.
From 2000 to 2022, the Health Effects of Arsenic Longitudinal Study (HEALS) followed thousands of adults in Araihazar, Bangladesh, a region where shallow tube wells often contain elevated arsenic levels. The project, led by scientists from Columbia University, the Columbia Mailman School of Public Health and New York University, tested more than 10,000 wells and repeatedly measured arsenic in participants' urine to track internal exposure over time.
According to the study team, people whose urinary arsenic levels fell from high to low experienced mortality rates comparable to participants with consistently low exposure throughout the study period. The size of the reduction in arsenic exposure was closely tied to how much the risk of death from chronic diseases declined, including deaths from heart disease and cancer. These patterns held even after researchers accounted for age, smoking and socioeconomic factors. By contrast, those who continued using high-arsenic water did not see a reduction in chronic disease mortality.
"We show what happens when people who are chronically exposed to arsenic are no longer exposed," said co-lead author Lex van Geen of the Lamont-Doherty Earth Observatory, part of the Columbia Climate School. "You're not just preventing deaths from future exposure, but also from past exposure."
Over the course of the study, national and local programs that labeled wells as safe or unsafe, along with the installation of safer sources, contributed to a substantial drop in arsenic exposure in Araihazar. Arsenic concentrations in commonly used wells fell by about 70 percent, and average urinary arsenic levels among participants declined by roughly 50 percent, a change that persisted through 2022.
In Bangladesh, an estimated 50 million people have consumed water exceeding the World Health Organization guideline of 10 micrograms per liter of arsenic, a crisis the WHO has described as one of the largest mass poisonings in history.
Co-lead author Fen Wu of NYU Grossman School of Medicine said the two decades of detailed health and exposure data provided some of the clearest evidence to date that lowering arsenic exposure reduces mortality risk. Joseph Graziano, principal investigator from the Columbia Mailman School of Public Health, reflected on the broader implications: "Seeing that our work helped sharply reduce deaths from cancer and heart disease, I realized the impact reaches far beyond our study to millions in Bangladesh and beyond now drinking water low in arsenic."
The researchers compared the health benefits of lowering arsenic exposure to those of quitting smoking, noting that risks do not disappear immediately but fall gradually as exposure declines.
To expand access to safer water, the team is working with Bangladeshi authorities to make well data more widely available. They are piloting NOLKUP ("tubewell" in Bangla), a free mobile app built from more than six million well tests, which allows users to check arsenic levels and depths for individual wells, find nearby safer options and help officials identify communities in need of new or deeper wells.
Co-author Kazi Matin Ahmed of the University of Dhaka said, "Our findings can now help persuade policymakers in Bangladesh and other countries to take emergency action in arsenic 'hot spots'."
Arsenic contamination of groundwater is a global problem, and Columbia researchers note that more than 100 million people in the United States rely on groundwater that can contain arsenic, particularly in areas served by private wells. The study suggests that investments in testing, labeling and improving drinking water sources can deliver substantial and lasting reductions in chronic disease deaths within a single generation.
