Rice makes up 20 percent of caloric intake worldwide. Although this staple crop is inexpensive and filling, rice tends to contain large amounts of arsenic. The greatest problem is in Southeast Asia, especially Cambodia, where rice can make up more than 70 percent of the calories in typical diets. Many Cambodians live in regions that are affected by high arsenic levels in drinking water, exposure to which is linked to cardiovascular disease, cancer and other deadly diseases. Recent evidence suggests rice also is a significant source of arsenic to humans, particularly for people who consume large quantities of rice. Rice often contains arsenic because the biochemical processes associated with the annual flooding of rice paddies (soils where rice is grown) produce dissolved arsenic that is mistakenly incorporated into rice plants as they take in nutrients.
This summer, as interns in the Center for Climate and Life at the Lamont-Doherty Earth Observatory of Columbia University, we have worked to quantify the complex effects of climate on arsenic accumulation in rice. The idea is simple: Climate affects flooding and biological processes in flooded soils, and thus can affect the chemical cycling of arsenic in soils and its uptake into rice. However, it is not straightforward to test our thesis because there are many other factors that can impact rice arsenic levels. For example, agricultural systems are constantly affected by farming practices such as irrigation, choice of rice variety and fertilizer use, most of which are not reported in studies measuring arsenic in rice. The information we obtain will help understand the processes that regulate arsenic levels, but our main goal is to use that knowledge to educate farmers and policymakers about adaptations that would help make rice production more sustainable and healthier into the future. Hopefully, our presented research will also raise awareness about the effects of arsenic in rice, and empower people to address this problem from the roots up (pun intended).
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