Around 71 per cent of wells in Myanmar's Ayeyarwady Delta exceed World Health Organization (WHO) safe drinking water limits, putting millions at risk
Arsenic contamination is highest in the mid-central regions of the Ayeyarwady Delta, especially in areas with dense networks of streams and depressions
The study calls for blanket screenings of wells in high-risk areas as this is essential to protect people's health from arsenic
Twelve million people in Myanmar's Ayeyarwady Delta face serious long-term health risks from the harmful substance arsenic, in their drinking water.
The study, led by the University of Portsmouth, analysed national screening data from nearly 124,000 wells and found that 71 per cent exceed safe drinking water limits set by the World Health Organization (WHO), threatening the country's goal of providing safe water for all by 2030.
Published in GeoHealth , the study draws on 81 water samples collected across a 170- kilometre stretch of the delta to examine where and why arsenic contamination occurs. This data was used to build a predictive model that identifies landscape features associated with arsenic hotspots.
The study found that only 8 per cent of wells in Myanmar exceed the national safety limit of 50 micrograms per litre, yet a much larger proportion surpasses the World Health Organization (WHO) guideline of 10 micrograms per litre. This indicates that many communities are using water considered safe under national standards yet still face elevated long-term health risks under international benchmarks.
This also has major implications for Myanmar's goal of expanding access to safe drinking water within the next five years, as prolonged exposure to even low levels of arsenic is linked to chronic health effects that may develop gradually over time.
The researchers also found that arsenic concentrations are highest in the mid-central areas of the delta, where dense networks of interconnected streams and shallow depressions are common. These features collect organic matter at the surface and channel it into the shallow groundwater. This organic matter is likely to fuel the chemical process that releases arsenic from the sediments into the water, creating areas of elevated risk.
The study identified these locations as arsenic hotspot zones where well testing and safe water interventions would be most effective. It also found that areas with steeper slopes typically have lower arsenic levels because faster water flow helps flush the arsenic away.
Arsenic levels in the Ayeyarwady Delta are often moderate rather than extremely high, as observed in some other Asian river deltas. However, a large proportion of wells in Ayeyarwady still exceed the World Health Organization guideline. This means exposure is widespread, and long-term health effects can develop gradually across many communities.
Dr Mo Hoque from the University of Portsmouth's School of the Environment and Life Sciences , said: "Our study shows how organic matter from the land surface is transported into shallow aquifers, where it plays an important role in the conditions that allow arsenic to enter groundwater. This adds new evidence to an ongoing scientific discussion about the origin of the organic matter involved in the spread of arsenic.
"By examining the Ayeyarwady Delta as a whole, we provide the first comprehensive picture of arsenic distribution across the region. It highlights the urgent need for widespread testing to identify risks and protect communities."
Professor Dr Khin Kay Khaing, from the University of Magway, added: "In many villages, households rely on shallow wells for drinking and cooking water. Arsenic cannot be seen, tasted, or smelled, so people often use water without knowing the risk.
"The effects of arsenic exposure develop slowly, so the risks are not always recognised in the community."
The study underscores the need for comprehensive testing in identified high-risk areas, efforts to reduce arsenic levels in contaminated wells, and stronger support for Myanmar's safe water initiatives.
"Our findings call for urgent international attention, as many rural communities, especially children, are unknowingly exposed to unsafe drinking water," added Dr Hoque.
"We hope this study will help drive policy changes and encourage organisations such as UNICEF to tackle this growing public health issue."
