Professor warns against arsenic ‘on your plate’
By Stephen Kirkpatrick, The Dartmouth Staff
Published on Friday, September 24, 2010
High levels of arsenic in rice and rice products present serious hazards to public health, University of Aberdeen professor Andy Meharg said in a seminar on Thursday. Meharg discussed the dangers and pervasiveness of arsenic, which has long been linked with cancer, in a seminar, “Arsenic on Your Plate,” in Filene Auditorium.
Although health organizations and governments have stressed the need to regulate arsenic levels in water, Meharg said there are no corresponding standards for arsenic in food. He cited research to demonstrate that rice is particularly susceptible to arsenic contamination and that diets heavy in rice can be related to arsenic-related health conditions, including cancer.
Rice absorbs a substantially larger amount of arsenic than other crops because the water used to flood rice paddies is able to “mobilize” arsenic from the soil, Meharg said. Arsenic can occur in the soil naturally or collect there as a result of runoff from industrial and mining sites, he said.
Levels of arsenic contamination are higher in rice grown in the United States than in any other nation, according to research Meharg cited in his lecture. Rice from the South, specifically Arkansas and Texas, shows the highest rates of arsenic poisoning because of the arsenic-laden chemicals farmers previously used to cultivate cotton there, he said.
Not all rice products contain the same amounts of arsenic, according to Meharg. Products such as rice bran, rice milk and brown rice, which are made with the husks of rice grains, pose a far higher risk than the “polished rice,” or white rice that is consumed in much of the world, he said.
Many of these products, he added, are consumed by children, observing that UNICEF distributes a large amount of rice bran, most of it likely contaminated, to impoverished children through its relief programs.
Meharg helped conduct one study that showed that almost all rice milk has higher arsenic content than most water supplies, he said. These findings prompted the United Kingdom to recommend that children younger than four and a half years not consume rice milk at all.
Arsenic is a “non-threshold carcinogen,” meaning that exposure to any amount of arsenic poses a health risk, Meharg said.
Despite this contamination, Meharg said little has been done to control arsenic in rice products. Both the United States and European Union limit arsenic in water to 0.1 milligrams per kilogram per day, but no comparable standards have been set for food supplies, according to Meharg.
Meharg concluded that more efforts must be made to regulate arsenic in rice, since it is a major food supply for most of the world. Food regulations must take into account different types of arsenic — “inorganic” arsenic found in sediments is much more dangerous than the “organic” variety seen primarily in seafood — and must take into account higher rice-consumption rates for high-risk groups like young children, gluten- and lactose-intolerant people and people of Asian descent.
Meharg has focused his research on the biogeochemistry of arsenic, paying particular attention to the passage of arsenic from soils and sediments into food chains, according to his website.
Dartmouth’s Toxic Metals Superfund Research Program, which studies the occurrence of arsenic and other toxic metals in the environment, sponsored the event.