Unhealthy levels of arsenic in water could exacerbate health concerns when used to boil rice

A new study underlines the risk of using water contaminated with arsenic to cook rice, a staple food serving more than half the world’s population. It highlighted that 32 per cent of the global population lives in low- and middle-income countries that do not adhere to the World Health Organization’s recommended limits.

The study, conducted by the University of Sheffield’s Institute for Sustainable Food and the Department of Geography (United Kingdom), pointed out that some countries still follow the outdated WHO standard of 50 parts per billion as a safe threshold for arsenic in drinking water. Professor of soil and environmental science and lead author Manoj Menon mentioned in a statement that there is often very little or no regulation to current WHO standards.

Menon added that India is among 40 other countries that adopted 10 parts per billion as its standard. However, 19 other countries have no evidence of any regulations.

Rice contains more arsenic in comparison to other cereals. The world’s most widely consumed grain contains inorganic arsenic (iAs) — a Group 1 carcinogen according to the International Agency for Research on Cancer, a part of WHO. This poses a significant health concern when rice is cooked with water that has unhealthy amounts of arsenic. Prolonged exposure can lead to even diabetes and cardiovascular diseases.

The researchers showed how different cooking techniques affected the absorption of arsenic from the water. When the rice was cooked with excess water with rice to rice-to-water ratio of 1:6–12 or with percolating cooking water, it was effective at removing arsenic to a significant extent in both white and brown rice.

In the other method, referred to as the parboiled and absorbed method, unwashed rice was added to de-ionised water and it was left to simmer for 5 minutes, after which the water was filtered out to remove arsenic on the surface.

They found that white and parboiled rice absorbs more arsenic than brown rice, demonstrating that the population in Western countries and Asia is more at risk of suffering health consequences.

“This significant result suggests that brown rice could be a safer choice in regions with limited availability of iAs-safe water for cooking, reducing risk to vulnerable populations,” the researchers said in their paper.

“We hypothesise that the bran layer in brown rice may act as a physical or chemical barrier, preventing the accumulation of iAs in the starchy interior part of the cooked rice, whereas in white or parboiled rice (both without the bran), the rice grain is likely to absorb and accumulate more iAs from the cooking water,” the researchers added. Iron and Manganese are abundant in bran, and these elements may bind with iAs, they said.

The researchers recommended that countries with high per capita rice consumers — like Bangladesh — should have policies in place that ensure the supply of water does not have much arsenic, particularly for domestic consumption.

Where possible, 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 is required in countries with high levels of arsenic in water, Menon recommended.