The use of contaminated water with high levels of arsenic poses a severe health risk to millions of people around the world, according to a study published in Science of the Total Environment.
A team of researchers from the University of Sheffield, UK, has found that some countries don’t follow the current World Health Organisation (WHO) recommended arsenic levels in the water and are putting their population at risk. Around 32% of the global population – particularly those from low and middle-income countries – have a high risk of developing serious health issues caused by high levels of arsenic.
These countries still follow outdated WHO recommendation levels (50 µg L-1 or parts per billion) that were introduced in 1963, including several Asian countries such as China, Bangladesh, Pakistan, Cambodia, Thailand, Myanmar, and Nepal.
Long-term exposure to high arsenic in water can cause a wide range of health problems, including cancer, diabetes, pulmonary issues, and cardiovascular diseases. As many of the affected countries use rice as a staple diet, the authors wanted to examine how different methods of cooking rice using water contaminated with arsenic affected the amount absorbed into the food.
“Both rice and drinking water in the UK are regulated for arsenic, but further afield in Asia and Africa, there is often very little or no regulation to current WHO standards. We know that as many as 40 countries in the world allow more than ten parts per billion in drinking water, and 19 countries have no evidence of any regulations,” said Dr. Manoj Menon from the University of Sheffield’s Institute for Sustainable Food and the Department of Geography. “Rice is one of the major cereal crops in the world, contributing to the dietary energy and nutrition of more than half of the world’s population. We already know that rice has more arsenic than other cereals, and the risk is exacerbated if we cook rice with arsenic-contaminated water above the WHO recommended limit. That is why it is vitally important that countries worldwide work to adopt the latest WHO recommendations to ensure arsenic exposure is minimised as much as possible to protect the public.”
The authors tested water with varying levels of inorganic arsenic — including 10 and 50 µg L-1 and arsenic-safe tap water from the UK ( which contains less than 0.2 parts per billion) as a control — which was then used to cook different types of rice. Results showed that white boiled rice accumulates more arsenic than brown rice, and the levels in the rice increased as the levels of arsenic in the water increased.
“India has a huge population that was affected by an arsenic problem, and a few years ago, it adopted ten parts per billion as its standard, setting a good example for the other countries that are yet to adopt this,” said Dr Menon. “Obviously, for people in countries where rice is a staple food, consumption is higher, and the health risk also increases, such as in many parts of Asia. People in the UK may only consume around 5kg of rice annually, but the average global consumption is 57kg, and even higher at 85kg across Asia. “In this study, we evaluated the exposure risks to the Bangladesh population–the highest per capita rice consumers in the world at approximately 170 kg per person, and found that nearly all age groups are at significant risk. Policymakers in those countries with high rice consumption rates urgently need to develop measures to supply arsenic-safe water for domestic use.”
In this study, the authors also compared two of the most commonly used methods to cook rice: using excess water vs. parboiled and absorbed. Results showed that the safest way to cook rice if there is an issue with arsenic levels in the water is to use rice with excess water. This means the water is drained off when the rice is done (like pasta or noodles) and is not completely absorbed by the rice.
“One of the United Nations (UN) Sustainable Development Goals for good health and wellbeing is for everyone to have access to clean water and sanitation. This cannot happen without regulations being implemented in countries where limits or water testing are not currently in place,” concluded Dr Menon. “There are genuine concerns for rice consumers about consuming arsenic, but our successive studies have shown there are ways we can try to minimise our risk of exposure. Even in countries where there may be higher levels of inorganic arsenic in water supplies, where possible, this includes selecting varieties of rice that don’t absorb as much arsenic and using cooking methods that remove as much arsenic from the water and grains as possible.”
Menon M, Nicholls A, Smalley A, Rhodes E. A comparison of the effects of two cooking methods on arsenic species and nutrient elements in rice. Sci Total Environ. 2024 Mar 1;914:169653. doi: 10.1016/j.scitotenv.2023.169653.