Arsenic and Old Rice: Should We Worry About a Toxic Chemical in a Popular Food?

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Arsenic is nasty stuff. Concentrated doses of the chemical can be fatal — one reason it’s long been a popular poison for assassins and unhappy widows. And chronic high exposure has been linked to skin lesions, certain cancers and cardiovascular disease. But scientists are increasingly concerned about even low-dose exposures [PDF], especially for pregnant women, finding that prenatal arsenic exposure is linked to infant mortality and low-birth weight.

The most common route of exposure to arsenic is through drinking water, in part because groundwater can be contaminated with the naturally occurring chemical. But in a new study published in the Proceedings of the National Academy of Sciences, researchers have found that eating rice can also lead to arsenic exposure, raising questions about how much of the chemical may be making its way into the food supply — posing special risks to pregnant women and their children.

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The study, led by Margaret Kargas and Diane Gilbert-Diamond of the Children’s Environmental Health and Disease Prevention Center at Dartmouth Medical School, looked at 229 pregnant women in New Hampshire whose urine had been tested for arsenic concentration. Seventy-three of those women reported consuming rice, averaging about half a cup a day of cooked rice, while 156 women did not eat rice. The tap water in each subject’s home was also tested for arsenic.

The researchers found that the women who ate rice daily showed median arsenic levels of 5.27 micrograms per liter, while the non-eaters showed a median level of 3.38 mcg per liter. That’s a statistically significant difference, though it’s important to note that even the rice eaters were well below the Environmental Protection Agency (EPA) standard of 10 mcg per liter. Less good: more than 10% of the women in the study had drinking water with arsenic levels above those EPA standards.

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This is an early study, and the researchers note that arsenic levels in rice likely vary widely around the country. (Rice can absorb arsenic via groundwater more efficiently than other crops.) But while the average American eats half a cup of rice a day, some ethnic groups eat far more, with Asian Americans averaging more than 2 cups a day. It doesn’t help that the U.S. and the E.U. — unlike China — have no statutory limits on arsenic levels in rice.

Says Terry Punshon, a researcher assistant professor of biological sciences at Dartmouth and a co-author of the study:

While this study reveals the potential for exposure to arsenic from rice, much additional research is needed before we can determine if there are actual health impacts from this source of exposure. Rice is a nutritious food source worldwide. Ultimately any health risks, if found, would then need to be weighed against the obvious nutritional benefits of rice consumption.

In other words, don’t react to this study by instantly cutting out rice from your diet — especially if you’re going to replace it with something less healthy. But the EPA and other government bodies should be doing more to ensure that our rice supply isn’t tainted by a poison.

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