Rising temperatures combined with increasing levels of carbon dioxide in the air could cause higher arsenic concentrations in rice, with toxicological effects on those who consume it.
Rice is consumed by half the world's population and is a staple food for billions of people, particularly in Asia, but its nutritional quality could deteriorate due to climate change, reaching even toxic levels through the excessive absorption of arsenic.
This picture has emerged from a study by Chinese and American researchers published in The Lancet Planetary Health. The findings indicate that a temperature increase of more than 2°C combined with rising levels of carbon dioxide (CO2) in the atmosphere leads to an increase in inorganic arsenic concentrations in rice, potentially raising health risks over a lifetime for Asian populations by 2050.
For ten years, researchers cultivated rice in controlled fields, exposing it to varying levels of carbon dioxide and temperature. They found that as both levels rose, in line with climatologists' projections, so too did the amount of inorganic arsenic in rice grains. The researchers then took data from their field experiments and, based on per capita rice consumption in seven Asian countries — Bangladesh, China, India, Indonesia, Myanmar, the Philippines and Vietnam — calculated how disease risk could also increase. According to estimates, China is projected to record the highest number of cancer cases, with an estimated 13.4 million cases linked to exposure to arsenic from rice.
Rice contamination with arsenic is a well-known issue: arsenic is a naturally occurring metal absorbed by rice from the soil and the water in which it is submerged. The hypothesis is that climate change would alter the microbiome of the soil, causing higher arsenic concentrations in rice. The toxicological effects of chronic arsenic exposure include lung, bladder and skin cancers, as well as ischaemic heart disease. Emerging evidence also suggests that arsenic exposure may be linked to diabetes, adverse pregnancy outcomes, neurodevelopmental problems and effects on the immune system.
"There is a toxicological effect of climate change on rice and consumption is one of the factors that determines vulnerability to this effect," said Lewis Ziska, professor at the Columbia Mailman School and one of the study's authors. "Since rice is a staple food in many parts of the world, this increase in arsenic levels could lead to a substantial rise in the global burden of cancer, cardiovascular disease and other health problems related to this substance."
According to the researchers, the findings highlight how climate change continues to affect global food security and how urgent it is to act to reduce arsenic exposure in rice. Among the proposed solutions are improved soil management in rice paddies and better processing practices, alongside public health initiatives focused on consumer education and exposure monitoring.