As the world's population increases, demand for staple crops such as rice will also rise. However, in parts of the world where the majority of rice is currently grown and eaten, high levels of arsenic in rice may compromise the health of millions of people. Understanding the factors that influence arsenic uptake in rice plants will help scientists and farmers develop agricultural practices that minimize the risk of arsenic contamination.

With this in mind, a team of researchers from the University of Delaware and Stanford University collaborated on studies to determine baseline arsenic concentrations in Cambodian rice and to identify soil characteristics that reliably predict arsenic uptake. The team found that the amount of oxygen present in the soil, a condition often mediated by microbes in flooded rice paddies, seemed to be the most important factor related to arsenic uptake. As Cambodian farmers face growing demand for rice in the future, these findings will help to determine the best locations and practices for maximizing rice yields while minimizing arsenic contamination.

Soils that developed from silt left behind in river valleys in South and Southeast Asia contain naturally occurring arsenic, which is released under certain biogeochemical conditions such as those occurring in flooded rice paddies. Rice plants grown in these soils take up the arsenic through their roots and transfer it to the grains. Much of the work on arsenic in rice has been conducted in Bangladesh and India, where farmers commonly raise up to three rice crops per year by irrigating their fields during the dry season. When groundwater used for irrigation is also contaminated with arsenic, concentrations of arsenic in rice may be even more elevated.