8 Minutes
A 20-year investigation in Bangladesh shows that reducing arsenic levels in drinking water can halve deaths from cancer, cardiovascular disease and other chronic illnesses — even among people who lived with high exposure for decades. The findings, drawn from individual-level monitoring of nearly 11,000 adults, offer the most direct long-term evidence yet that cleaning up groundwater translates into rapid health gains.
How a long-term project tracked exposure and survival
The Health Effects of Arsenic Longitudinal Study (HEALS) followed thousands of residents in Araihazar, Bangladesh, from 2000 through 2022. Researchers combined repeated testing of more than 10,000 local tube wells with periodic measurements of urinary arsenic — a reliable biomarker of internal exposure — and carefully recorded causes of death over two decades. That person-by-person approach let scientists compare long-term outcomes for people who switched to low-arsenic water sources with those who continued drinking contaminated well water.
Because arsenic is tasteless and odorless in water, many households were unaware of chronic exposure. Community and national well-testing campaigns, however, labeled wells as safe or unsafe and encouraged households to change sources. Some families installed private, deeper wells; others moved to neighboring safer wells. That real-world variation created a natural experiment embedded in a sustained, prospective study.
Major findings: deaths fell as arsenic exposure dropped
Across the study population, reductions in arsenic in local wells averaged about 70 percent, and urinary arsenic — the internal dose — fell by roughly 50 percent on average. Participants whose urine measurements fell from high to low showed a remarkable result: their mortality risk from chronic diseases aligned with people who had low exposure throughout the study. Conversely, those who kept drinking high-arsenic water saw no improvement in mortality risk.
These associations persisted after adjusting for age, smoking, socioeconomic status and other factors. The pattern was dose-responsive: the larger the decline in arsenic biomarkers, the greater the drop in death risk. Authors of the paper in JAMA framed the effect as comparable to quitting a major environmental risk: harms from past exposure don’t vanish instantly but fall steadily once exposure stops.
Why this matters globally
Arsenic in groundwater is not just a Bangladeshi problem. Many regions around the world rely on aquifers that contain naturally occurring arsenic. In the United States, over 100 million people get water from aquifers that may contain arsenic, including many private well users who lack routine testing and treatment. The World Health Organization’s guideline for arsenic in drinking water is 10 micrograms per liter; in parts of Bangladesh, tens of millions of people have historically consumed water well above that level. WHO has called the crisis in Bangladesh one of the largest mass poisonings in history.
From a public health perspective, the HEALS results provide a powerful, actionable message: investments in testing, labeling, well replacement and community guidance can yield measurable reductions in deaths within a generation. Policymakers and water managers can use this evidence to prioritize emergency action in arsenic hot spots and to expand low-cost monitoring and remediation programs.
Study methods that strengthen the evidence
Two features of HEALS give confidence in the conclusions. First, the repeated urinary tests provided an objective measure of what people actually ingested, not just the arsenic concentration of nearby wells. Second, the long follow-up — two decades — captured the delayed nature of many chronic diseases, allowing researchers to observe how risk evolved after exposure dropped.
During the project, map-based well surveys and community outreach created spatial and temporal patterns of exposure change. That variability, combined with careful mortality surveillance, allowed researchers to make comparisons that approximate an intervention trial while reflecting real-life choices and constraints.
As Lex van Geen of Lamont–Doherty Earth Observatory, a co-lead on the study, put it: "You’re not just preventing deaths from future exposure, but also from past exposure." Fen Wu of NYU and other co-authors noted that this is the strongest long-term human evidence linking arsenic reduction to lower mortality.
From data to tools: NOLKUP and policy steps
Beyond publishing results, the research team has worked to translate data into usable tools. In collaboration with Bangladeshi partners, they developed a free app called NOLKUP (Bangla for "tubewell") built from millions of well tests. The app lets users search well locations, view arsenic concentrations and depths, and find nearby safer sources. Planners can use the data to target deeper well drilling where it will help most.
Co-author Kazi Matin Ahmed emphasized the policy implications: evidence that health risks decline after exposure reduction should motivate emergency remediation in the worst-affected districts. Practical measures, the study shows, include widespread well testing, visible labeling of unsafe wells, subsidized deeper wells or piped-water connections, and community education about safer sources.
Scientific context: arsenic, biomarkers and health outcomes
Arsenic is a naturally occurring metalloid that enters groundwater through geological processes. Chronic ingestion is linked to cancers (especially skin, lung and bladder), cardiovascular disease, diabetes, and other long-term conditions. Urinary arsenic reflects recent ingestion and is often combined with toenail or hair measures for longer-term exposure assessment.
The HEALS work supports toxicological and epidemiological literature that links arsenic to a spectrum of chronic outcomes and shows that exposure cessation yields benefits. The risk trajectory after stopping exposure appears similar to other environmental hazards: a gradual but meaningful reduction over years, not an instant reset.
Expert Insight
"This study is one of the clearest demonstrations that clean water investments save lives," says Dr. Maya Singh, an environmental epidemiologist who was not involved in the research. "What stands out is the combination of high-quality exposure data and long-term follow-up: it turns the conversation from abstract risk to concrete lives saved. For countries facing similar groundwater challenges, the policy question is no longer whether to act, but how quickly and where to invest."
What comes next: research and implementation
Future work will refine estimates of which interventions are most cost-effective in different hydrogeological settings and how quickly mortality and morbidity decline after switching sources. Ongoing monitoring of households that adopted deeper or alternative water sources will clarify long-term behavioral and infrastructural barriers. Meanwhile, expanding real-time well mapping, improving the affordability of point-of-use filtration, and enhancing community outreach can accelerate benefits.
Joseph Graziano, the principal investigator of the NIH-supported program, reflected on the long arc of the project: "Seeing that our work helped sharply reduce deaths from cancer and heart disease, I realized the impact reaches far beyond our study — to millions now drinking water low in arsenic." Ana Navas-Acien of Columbia added that long-term sample and data stewardship made the findings possible, underscoring the value of sustained funding for environmental health research.
For communities and policymakers, the message is actionable and urgent: testing wells, marking unsafe sources, enabling access to deeper or treated water, and using mapping tools can cut the burden of chronic disease substantially. The HEALS findings transform a decades-long public health emergency into a roadmap for measurable recovery — and show that even long-standing exposures can be reversed to save lives.
Source: scitechdaily
Comments
skyspin
Is urinary arsenic a good long-term marker tho? Looks solid, but could lifestyle, migration or access to treatment skew results? Curious if they adjusted...
bioNix
Wow this really hit me. Cutting arsenic cut deaths in half? That's insane, finally proof that testing+wells matter. But so much damage already, frustrated
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