Arsenic in rice: Part III—Tracing the sources of arsenic 11/12
(This article is adapted from the November 2012 Consumer Reports magazine.)
Part I—Test results | Part II—How to cut your risk | Part III—Tracing the sources of arsenic
Rice absorbs arsenic from soil or water much more effectively than most plants. That’s in part because it is one of the only major crops grown in water-flooded conditions, which allow arsenic to be more easily taken up by its roots and stored in the grains.
In the U.S. as of 2010, about 15 percent of rice acreage was in California, 49 percent in Arkansas, and the remainder in Louisiana, Mississippi, Missouri, and Texas. That south-central region of the country has a long history of producing cotton, a crop that was heavily treated with arsenical pesticides for decades in part to combat the boll weevil beetle. (See infographic: How arsenic gets into rice.)
“Extensive surveys of south central U.S. rice, by more than one research group, have consistently shown that rice from this region is elevated in inorganic arsenic compared to other rice-producing regions,” says Andrew Meharg, professor of biogeochemistry at the University of Aberdeen in Scotland and co-author of the book Arsenic and Rice. “And it does not matter, relative to risk, whether that arsenic comes from pesticides or is naturally occurring.”
High levels of arsenic in soil can actually reduce rice yields. Meharg, a leading researcher in the field, notes the Department of Agriculture has invested in research to breed types of rice that can withstand arsenic. That may help explain the relatively high levels of arsenic found in rice from the region, though other factors such as climate or geology may also play a role.
The USA Rice Federation tells consumers that there is no reason to be concerned about arsenic in food. Its website states that arsenic is “a naturally occurring element in soil and water” and “all plants take up arsenic.”
But “natural” does not equal safe. Inorganic arsenic, the predominant form of arsenic in most of the 65 rice products we analyzed, is ranked by the International Agency for Research on Cancer (IARC) as one of more than 100 substances that are Group 1 carcinogens. It is known to cause bladder, lung, and skin cancer in humans, with the liver, kidney, and prostate now considered potential targets of arsenic-induced cancers.
Though arsenic can enter soil or water due to weathering of arsenic-containing minerals in the earth, humans are more to blame than Mother Nature for arsenic contamination in the U.S. today, according to the federal Agency for Toxic Substances and Disease Registry. The U.S. is the world’s leading user of arsenic, and since 1910 about 1.6 million tons have been used for agricultural and industrial purposes, about half of it only since the mid-1960s.
Residues from the decades of use of lead-arsenate insecticides linger in agricultural soil today, even though their use was banned in the 1980s. Other arsenical ingredients in animal feed to prevent disease and promote growth are still permitted. Moreover, fertilizer made from poultry waste can contaminate crops with inorganic arsenic.
Rice is not the only source of arsenic in food. A 2009-10 study from the EPA estimated that rice contributes 17 percent of dietary exposure to inorganic arsenic, which would put it in third place, behind fruits and fruit juices at 18 percent, and vegetables at 24 percent. A more complete study by the European Food Safety Authority found cereal products could account for more than half of dietary exposure to inorganic arsenic, mainly because of rice.
Related links
Arsenic in rice: Part I--Test results; Part II--How to cut your risk 11/12
Download this PDF with complete details of the test results.
New study finds arsenic in infant formula, cereal bars. 2/12
Consumer Reports discloses additional data from its arsenic tests. 12/11
Part I—Test results | Part II—How to cut your risk | Part III—Tracing the sources of arsenic
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