How can health risks from arsenic be identified and reduced?
In many parts of the world groundwater is used for drinking, cooking and irrigating crops, and the level of arsenic it contains is a major health risk. Continual exposure to high concentrations of arsenic in water can result in people developing cancers, ischaemic heart disease and compromised immune systems. This is particularly marked in countries such as Bangladesh, where it is estimated that tens of thousands of people die prematurely each year because of chronic exposure to this carcinogenic hazard. However, risks also exist in the UK, for example to users of private water supplies in the South West of England, and to groups with a high rice diet.
To address the risks posed by arsenic-contaminated groundwater, we need to understand how arsenic enters water sources, assess the risk it poses and raise public awareness of those risks.
With funding from multiple sources, the University of Manchester brought geochemists and microbiologists together on various research projects to better understand the extent and origins of this problem in different parts of the world.
In Bengal, the researchers discovered that indigenous metal-reducing bacteria are critical to the processes, driving the transfer of arsenic into groundwater, where they can represent a significant health risk to those using contaminated water for drinking or cooking. The research helped predictive groundwater arsenic hazard maps to be developed. In Bengal, the researchers also analysed arsenic concentration in local rice and average levels of consumption to calculate typical exposure. They not only discovered that rice is a major exposure route for arsenic in humans in some affected areas but that it is also associated with elevated levels of genetic damage..
In the UK, research has shown that arsenic exposure from rice raises potentially significant health concerns in groups with high rice diets. Working with the British Geological Survey (BGS) and Public Health England, research is also being carried out in South West England, where earlier studies revealed that over 5% of private water supplies contained arsenic at levels higher than the WHO provisional guide value.
In Cambodia, the research has helped Resource Development International, a local NGO, to help advise on alternative water sources for impacted populations, and has initiated consideration of new bioremediation technologies. The highlighting of arsenic concentrations in rice has been reflected by revised FAO recommendations on provisional weekly tolerable intake, and in explicit acknowledgement of the importance of rice as an arsenic exposure route by the European Food Safety Authority. In the UK, the discovery of high arsenic levels in private water supplies has helped inform PHE on arsenic exposure, and the risk of arsenic exposure via various routes is now publicly acknowledged.
NERC funded research is ongoing into (i) potential year-in-year increases in groundwater arsenic hazard in Asia as a result of masasive abstraction of groundwater; and (ii) assessment of arsenic exposure routes to UK population groups.