For the lead researcher, it is an academic and personal mission because he witnessed firsthand the constant struggle to find clean, arsenic-free water when he was a child in India.

Lead author Dr Jagannath Biswakarma, senior research associate at the University’s School of Earth Sciences, said: “There are millions of people living in regions affected by arsenic, as I was a child. This breakthrough could pave the way for the path to safer drinking water and a healthier future.”

Exposure to arsenic contamination is a huge environmental and public health problem in South and Central Asia and South America, where people depend on groundwater for drinking and farming. The most toxic and mobile form of arsenic, called arsenite, easily leaches into water supplies and can cause cancer, heart disease and other serious conditions.

Dr Biswakarma said: “I have seen the daily battle for drinking water in my hometown of Assam. It is very difficult to find sources of groundwater that are not contaminated with arsenic, so for me this research hits close to home. “It is an opportunity to not only advance science, but also better understand the scope of an issue that has affected so many people in my own community and around the world for many decades.”

Previously, scientists believed that arsenite could only be converted into a less harmful form, called arsenate, with oxygen. But this new study has shown that it can still be oxidized, even in the absence of oxygen, with small amounts of iron acting as a catalyst for oxidation.

Dr Biswakarma said: “This study presents a new approach to addressing one of the world’s most persistent environmental health crises by showing that naturally occurring iron minerals can help oxidise, reducing the mobility of arsenic, even under low oxygen”.

The study results revealed that arsenite could be oxidized by green oxide sulfate, a source of iron prevalent in low-oxygen conditions such as groundwater supplies. They also showed that this oxidation process is further enhanced by a chemical released by plants and commonly found in soils and groundwater.

“These organic ligands, such as citrate from plant roots, could play a critical role in controlling the mobility and toxicity of arsenic in natural environments,” Dr. Biswakarma added.

The implications of this discovery are particularly significant for regions of the Global South that face some of the highest levels of arsenic contamination in the world. In countries such as India and Bangladesh, the local geology is rich in iron and reducing conditions often dominate in groundwater systems, leading to high levels of arsenic contamination. In the Ganges-Brahmaputra-Meghna delta, which spans Bangladesh and eastern India, millions of people have been exposed to arsenic-contaminated groundwater for decades as the chemical enters the water through natural processes. .

Dr Biswakarma said: “Many households rely on tube wells and hand pumps, but these systems do not guarantee access to clean water. The water often cannot be used for drinking or other household tasks due to its toxicity, odor and discoloration. In addition, there is a constant financial burden associated with obtaining new tube wells or hand pumps. As a result, economically disadvantaged families continue to struggle to find safe water for their daily needs.

Similarly, the Mekong Delta and the Red River Delta in Vietnam face ongoing challenges due to arsenic contamination, which affects drinking water supply and agricultural productivity. Rice fields can become hotspots for arsenic exposure, as the toxic chemical can accumulate in the soil and be absorbed by rice plants, posing an additional health risk through food consumption.

“The research opens the door to developing new strategies to mitigate arsenic contamination. Understanding the role of iron minerals in arsenic oxidation could lead to innovative approaches for water treatment or soil remediation, using natural processes to convert arsenic into its least harmful form before it enters drinking water supplies,” said co-author Molly Matthews, who worked on the paper during her master’s degree in Environmental Geoscience at the University of Bristol.

Identifying the specific form of arsenic in a sample can be challenging. Even a small amount of oxygen can convert arsenite to arsenate, so it is vital to protect samples from exposure to air. Thanks to funding from the European Synchrotron Radiation Facility (ESRF), the team was able to perform these complex experiments at its XMaS synchrotron facility in Grenoble, France.

Co-author Dr James Byrne, Associate Professor of Earth Sciences, added: “Determining arsenic formation at the atomic level using X-ray absorption spectroscopy was crucial to confirming changes in the oxidation state of arsenic. “Therefore, the synchrotron played a critical role in supporting our findings, which have potentially broad implications for our understanding of water quality.”

This work at the University of Bristol was supported through a UK Research and Innovation (UKRI) Future Leaders Fellowship (FLF) awarded to Dr James Byrne. More research is now needed to explore how these findings can be applied in real-world settings.

Dr Biswakarma said: “The entire research team worked tirelessly on this project, working 24/7 shifts, even during Easter, to carry out the experiments in France.

“I truly believe that, with more work, we can find possible effective solutions and we are already making great progress in overcoming this major global problem. We are excited to investigate how this process could work in different types of soils and groundwater systems, especially in areas where arsenic contamination is most serious.

Finding bold answers to big questions relating to global challenges is at the heart of research at the University of Bristol. This study covers core themes, including advancing equitable and sustainable health and advancing social justice.