Climate change will make rice toxic, say researchers

For six years, Ziska and a large team of research colleagues in China and the US grew rice in controlled fields, subjecting it to varying levels of carbon dioxide and temperature. They found that when both increased, in line with projections by climate scientists, the amount of arsenic and inorganic arsenic in rice grains also went up.

Arsenic is found naturally in some foods, including fish and shellfish, and in waters and soils.

Inorganic arsenic is found in industrial materials and gets into water—including water used to submerge rice paddies.

Rice is easily inundated with weeds and other crops, but it has one advantage: It grows well in water. So farmers germinate the seeds, and when the seedlings are ready, plant them in wet soil. They then flood their fields, which suppresses weeds, but allows the rice to flourish. Rice readily absorbs the water and everything in it—including arsenic, either naturally occurring or not. Most of the world’s rice is grown this way.

The new research demonstrates that climate change will ramp up those levels.

“What happens in rice, because of complex biogeochemical processes in the soil, when temperatures and CO₂ go up, inorganic arsenic also does,” Ziska said. “And it’s this inorganic arsenic that poses the greatest health risk.”

Exposure to inorganic arsenic has been linked to cancers of the skin, bladder, and lung, heart disease, and neurological problems in infants. Research has found that in parts of the world with high consumption of rice, inorganic arsenic increases cancer risk.