Chronic Disease Risk Dropped 46% When People Made This One Change At Home

We all know drinking water quality matters, but most of us assume the damage from contaminated water is permanent once it's done. A new 20-year study1 tracking nearly 12,000 adults is challenging that assumption in a major way, and the implications reach far beyond the Bangladeshi community where the research took place.

The focus? Arsenic, a naturally occurring element that seeps into groundwater and has no taste, smell, or color. In the United States, more than 100 million people rely on groundwater sources that may contain this heavy metal, particularly those using private wells. You could be drinking arsenic-contaminated water right now and have absolutely no idea.

What makes this research particularly interesting is that it doesn't just look at preventing future exposure. It examines what happens when people who've been drinking contaminated water for years finally switch to clean sources. The results suggest our bodies may be far more resilient than we thought.

A 20-year, individual-level look at real exposure

Beginning in 2000, scientists enrolled ~11,700 adults living in Araihazar, Bangladesh, a region with a wide range of arsenic levels across shallow groundwater wells, from nearly zero to extremely high.

Rather than simply testing well water, researchers took a more precise approach. They measured arsenic in participants' urine up to five times throughout the study, providing direct evidence of internal exposure. They also tracked causes of death, creating a detailed picture of how changing exposure levels affected long-term health outcomes.

As community programs tested wells and labeled them safe or unsafe, many households switched to cleaner water sources, while others continued using contaminated wells. This created a natural comparison group within the study, allowing researchers to see exactly what happened when exposure decreased versus when it remained high.

The findings show dramatic risk reductions

Participants whose urinary arsenic levels dropped the most had:

But here’s the data point that really stands out. Compared with participants who continued drinking high-arsenic water, those who brought their levels below the median had:

And these benefits weren’t just for people who had always been low-exposure. Those who started out with high arsenic levels but switched to safer water ended up with the same mortality risk as those who had been low-exposure all along.

That suggests the body can recover (slowly, but meaningfully) once the source of exposure is removed.

Arsenic is a global problem

While this study took place in Bangladesh, the implications are global. Arsenic contamination affects groundwater worldwide, and in the U.S., it's particularly prevalent in private wells that aren't subject to EPA regulations the way public water systems are.

And even for those on city water, emerging contaminants (arsenic, PFAS, and other heavy metals) vary by region.

The good news? You can dramatically reduce exposure with smart filtration.

Simple ways to ensure your drinking water is safe 

Our top picks for water filters

If you’re ready to take action, these expert-backed filters consistently rank highest for removing arsenic, PFAS, and other contaminants:

The takeaway

This study is a powerful reminder that your environment shapes your health just as much as your habits do. Something as simple as switching to safer drinking water cuts the risk of dying from chronic disease by nearly half, even for people exposed for decades.

Clean water isn’t a luxury; it’s one of the most impactful health interventions we have.