Study links climate change to rising arsenic levels in paddy rice, increasing health risks

Climate change may significantly impact arsenic levels in paddy rice, a staple food for millions across Asia, reveals a new study from Columbia University’s Mailman School of Public Health. The research shows that increased temperatures above 2°C, coupled with rising carbon dioxide (CO₂) levels, lead to higher concentrations of inorganic arsenic (iAs) in rice, potentially raising lifetime health risks for populations in Asia by 2050.

Until now, the combined effects of rising CO₂ and temperatures on arsenic accumulation in rice have not been studied in detail. The research, done in conjunction with colleagues at Johns Hopkins Bloomberg School of Public Health and the Chinese Academy of Sciences, is published in The Lancet Planetary Health.

“Our results suggest that this increase in arsenic levels could significantly elevate the incidence of heart disease, diabetes, and other non-cancer health effects,” said Lewis Ziska, Ph.D., Columbia Mailman School associate professor of Environmental Health Sciences.

“As rice is a dietary staple in many parts of the world, these changes could lead to a substantial rise in the global burden of cancer, cardiovascular diseases, and other arsenic-related health issues.”

Ziska explained that the higher arsenic levels are likely due to climate-related changes in soil chemistry that favor arsenic that can more easily be absorbed into rice grain.

“From a health perspective, the toxicological effects of chronic iAs exposure are well established, and include cancers of the lung, bladder, and skin, as well as ischemic heart disease. Emerging evidence also suggests that arsenic exposure may be linked to diabetes, adverse pregnancy outcomes, neurodevelopmental issues, and immune system effects.”

In fact, “ingesting rice in regions like southern China and Southeast and South Asia is already a significant source of dietary arsenic and cancer risk,” said Ziska.

By measuring the effects of rising temperatures and CO₂ on 28 rice strains over 10 years in the field using FACE (Free-Air CO₂ Enrichment) methodology, and combining advanced modeling techniques, the team estimated inorganic arsenic doses and health risks for seven Asian countries: Bangladesh, China, India, Indonesia, Myanmar, the Philippines, and Vietnam.

Health risks were calculated for cancer and non-cancer outcomes. Estimates of rice availability in 2021 by country, as reported in Food and Agriculture Organization of the United Nations (FAO) food balance sheets, were used as the starting point for estimating rice ingestion. The standard deviation of rice ingestion per kg bodyweight from the U.S. Environmental Protection Agency data was used to create a normal distribution for each country.

The study’s projections for 2050 suggest a sharp rise in lifetime cancer cases, particularly lung and bladder cancers. China is projected to see the highest number of cases, with an estimated 13.4 million cancers linked to rice-based arsenic exposure.

“Based on our findings, we believe there are several actions that could help reduce arsenic exposure in the future,” Ziska noted.

“These include efforts in plant breeding to minimize arsenic uptake, improved soil management in rice paddies, and better processing practices. Such measures, along with public health initiatives focused on consumer education and exposure monitoring, could play a critical role in mitigating the health impacts of climate change on rice consumption.”

“Our study underscores the urgent need for action to reduce arsenic exposure in rice, especially as climate change continues to affect global food security,” says Ziska.