Clean water significantly reduces mortality from chronic diseases, even among people who have been exposed to arsenic for many years.

Key Research Findings

A large-scale 20-year study involving nearly 11,000 adults in Bangladesh found that lowering arsenic levels in drinking water is linked to a reduction in deaths from cardiovascular diseases, cancer, and other chronic illnesses by up to 50%. This research provides the strongest long-term evidence to date that reducing arsenic exposure can lower mortality, even among those who have consumed contaminated water for extended periods. The results were published in JAMA.

The Problem of Arsenic-Contaminated Water

Scientists from Columbia University, the Mailman School of Public Health, and New York University conducted an analysis focused on the pressing issue of arsenic contamination in water. Naturally occurring arsenic in groundwater remains a serious threat worldwide. In the United States, over 100 million people rely on groundwater that may contain arsenic, especially when using private wells. Arsenic is one of the most widespread chemical contaminants in drinking water.

As study co-author Lex van Geen from Lamont-Doherty, part of Columbia’s climate school, notes: “We show what happens when people who have long been exposed to arsenic stop receiving it. This prevents deaths not only from future exposure but also from past exposure.”

Long-Term Observations and Methods

Co-author Fen Wu from NYU School of Medicine emphasized that the data collected are the most convincing evidence yet of the link between reduced arsenic exposure and lower mortality risk. Over two decades, researchers closely monitored participants’ health and regularly measured arsenic levels in their urine, which improved the accuracy of the analysis.

Joseph Graziano, professor emeritus at the Mailman School of Public Health, remarked: “Seeing that our work helped sharply reduce deaths from cancer and cardiovascular disease, I realized the impact goes far beyond our study and affects millions in Bangladesh and other countries who now drink water with low arsenic levels.”

The Impact of Lowering Arsenic Levels

The mortality rate among people whose urinary arsenic levels dropped from high to low matched the rate of those who had low exposure throughout the study. The greater the reduction in arsenic, the more noticeable the decrease in mortality risk. Those who continued to drink water with high arsenic levels did not show a reduction in deaths from chronic diseases.

Arsenic naturally accumulates in groundwater and has no taste or smell, so people can drink contaminated water for years without knowing it. In Bangladesh, an estimated 50 million people have consumed water with arsenic levels exceeding the WHO guideline of 10 micrograms per liter. The World Health Organization has called this the largest mass poisoning in history.

The HEALS Study and Its Contribution

From 2000 to 2022, the HEALS project tracked thousands of adults in the Araihazar region of Bangladesh. More than 10,000 wells were tested, with arsenic levels ranging from very low to dangerously high. Researchers regularly measured participants’ urinary arsenic and recorded causes of death, allowing them to compare long-term health outcomes between those who reduced exposure and those who remained at high risk.

During the study, national and local programs labeled wells as safe or unsafe based on arsenic content. Many families switched to safer water sources or installed new wells, while others continued using contaminated water. This created a natural comparison group, helping researchers assess the effect of reduced exposure.

Long-Term Trends and Social Factors

Arsenic exposure in Araihazar dropped significantly during the study: concentrations in used wells fell by about 70% as many families sought cleaner water sources. Urine tests confirmed a corresponding 50% average reduction in internal exposure, a level that persisted through 2022.

These trends held even after accounting for differences in age, smoking, and socioeconomic factors. Participants who remained exposed to high levels or whose exposure increased over time continued to face a much higher risk of death from chronic diseases.

Comparison with Quitting Smoking

Researchers compared the health benefits of reducing arsenic exposure to those of quitting smoking. The risks do not disappear instantly, but gradually decrease as exposure is reduced.

Practical Measures and New Technologies

In Bangladesh, testing wells, marking hazardous sources, drilling private and deeper public wells have already improved water safety for many communities. As co-author Kazi Matin Ahmed from the University of Dhaka noted, the findings can help persuade policymakers in Bangladesh and other countries to take urgent action in arsenic “hotspots.”

To reach more families, the research team is working with the Bangladeshi government to make well data more accessible. They are piloting a free mobile app called NOLKUP (“tube well” in Bengali), built on over six million well analyses. Users can locate individual wells, view arsenic levels and depth, and search for safer options nearby. The tool also helps officials identify communities that need new or deeper wells.

Public Health Significance

The study shows that health risks can be reduced even for people who have been exposed to arsenic for years. This highlights an important opportunity: investing in clean water can save lives within a single generation.

Professor and chair of environmental health sciences at the Mailman School, Ana Navas-Acien, commented: “Sustained funding to support the collection, storage, and maintenance of valuable samples and data for over 20 years made this critically important work possible. Science is challenging—there were setbacks and difficulties along the way—but we managed to preserve the integrity of the samples and data even during funding gaps, which allowed us to demonstrate that preventing arsenic exposure can prevent disease.”