# Lowering Arsenic in Drinking Water Linked to Reduced Risk of Chronic Disease Deaths
A new 20-year study of nearly 11,000 adults in Bangladesh found that lowering arsenic levels in drinking water was associated with up to a 50 percent lower risk of death from heart disease,cancer and other chronic illnesses,compared with continued exposure. The study highlights the importance of ensuring access to arsenic-free drinking water and provides the first long-term,individual-level evidence that reducing arsenic exposure may lower mortality,even among people exposed to the toxic contaminant for years. The findings are published in *JAMA*.The landmark analysis, lead by researchers at Columbia University, Columbia Mailman School of Public Health and New York University, is crucial for public health because groundwater contamination from naturally occurring arsenic remains a serious issue worldwide. In the United States, more than 100 million people rely on potentially contaminated groundwater sources, especially private wells, for their drinking water. Arsenic is among the most common chemical pollutants.
“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, which is part of the Columbia Climate School. “You’re not just preventing deaths from future exposure, but also from past exposure.”
The results provide the clearest evidence to date of the link between arsenic reduction and lower mortality,according to co-lead author Fen Wu of NYU Grossman School of Medicine.For two decades, the research team followed each participant’s health and repeatedly collected urine samples to track exposure, which they say strengthened the accuracy of their findings.
> 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.A 1998 *New York Times* story first brought us to Bangladesh. More than two decades later, this finding is deeply rewarding-public health is often the ultimate delayed gratification.
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> Joseph Graziano, Professor Emeritus at Columbia Mailman School of Public Health and principal investigator of the NIH-funded program
People whose urinary arsenic levels dropped from high to low had mortality rates identical to those who had consistently low exposure throughout the duration of the study. The larger the drop in arsenic levels, the greater the decrease in mortality risk. By contrast, individuals who continued drinking high-arsenic water saw no reduction in their risk of death from chronic disease.
Arsenic is a naturally occurring element that accumulates in groundwater, and because it has no taste or odor, people can unknowingly drink contaminated water for years. In Bangladesh, an estimated 50 million people have been exposed to drinking water with levels above the world Health Organization’s guideline of 10 micrograms per liter.The WHO has called it the largest mass poisoning in history.
From 2000 to 2022, the Health Effects of Arsenic Longitudinal Study (HEALS) tracked thousands of adults and tested more than 10,000 wells in Araihazar, Bangladesh.