Smarter irrigation strategy reduces arsenic in rice without raising cadmium levels, study finds

TEMPE, Ariz. — A simple change in how rice fields are managed could make one of the world's most widely consumed staple foods safer to eat while conserving water and reducing greenhouse gas emissions, according to new research co-authored by an Arizona State University scientist.

The study found that rice grown in commercial fields managed with multiple periods of draining and re-flooding during the growing season had significantly lower arsenic concentrations without corresponding increases in cadmium, another toxic metal that can accumulate in crops.

The findings, published in Agricultural & Environmental Letters, provide field-scale evidence linking water management practices with arsenic and cadmium concentrations in rice grown under commercial farming conditions.

"One of my biggest concerns is making sure that we're not solving one problem by creating another problem," said Angelia Seyfferth, senior Global Futures scientist and professor in ASU's School of Life Sciences. "If farmers are doing these practices, it should be safer for people from a metals perspective, but it's also saving water. It also can decrease the amount of methane emissions that are coming from rice. It's kind of like everybody wins."

Rice feeds more than half of the global population, but it also accumulates more arsenic than other cereal grains because it is traditionally grown in flooded fields. Flooding creates oxygen-poor soil conditions that release naturally occurring arsenic from soil minerals, making it easier for rice plants to absorb. Long-term dietary exposure to inorganic arsenic has been linked to increased risks of several cancers and other health problems.

Researchers have long known that allowing rice fields to dry periodically can reduce arsenic uptake, but most previous studies were conducted under controlled experimental conditions. The new study evaluated whether those patterns were also observed across commercial farms, where soil types, weather and management practices vary.

Working with collaborators from the University of Delaware, the University of Arkansas and the U.S. Department of Agriculture, the research team analyzed 412 polished white rice samples collected from 60 commercial rice fields in Arkansas between 2018 and 2024. The research was supported by the Institute for the Advancement of Food and Nutrition Sciences.

The researchers categorized fields according to their water management practices: conventional continuous flooding, a single mid-season drainage event or multiple drainage events. Rice from fields that experienced multiple drying periods consistently had significantly lower arsenic concentrations than rice grown under conventional flooding.

Importantly, the water management practices were not associated with substantially higher cadmium concentrations, addressing a longstanding concern that efforts to reduce arsenic exposure could inadvertently increase another toxic metal. Cadmium concentrations remained well below international food safety limits.

The work also highlights the role of soil chemistry in controlling contaminant uptake by crops. As flooded soils dry, oxygen returns and iron minerals reform, binding arsenic and reducing its availability to rice plants.

"It's really the soil chemistry that's changing," Seyfferth said.

Beyond improving food safety, the water management practices evaluated in the study may also offer environmental benefits. Periodically drying rice fields can reduce irrigation water use while lowering methane emissions, a potent greenhouse gas generated under continuously flooded conditions.

Because many growers already incorporate drainage into their production schedules, the findings suggest that additional aeration events may offer a practical way to reduce arsenic accumulation while delivering environmental benefits.

The findings highlight how water management practices can influence contaminant uptake in rice and may help inform agricultural strategies that improve both food safety and environmental sustainability.