Arsenic in rice worrisome

By Dr. Ananya Mandal, MDDec 7 2011

Studies have shown that rice takes up more arsenic from soil than other crops. Now a new study shows that higher arsenic levels are ingested by women who eat as little as half a cup of cooked rice in a day. Currently, there are no limits on the amount of allowable arsenic in rice in the United States. But the Environmental Protection Agency has set arsenic limits in water of 10 parts per billion.

In a paper in this week’s Proceedings of the National Academy of Sciences, researchers report that women who ate the national average of half a cup of cooked rice a day in the two days prior to urine collection, ingested an amount of arsenic equivalent to drinking four and a quarter cups of water a day containing arsenic at the maximum allowable level set by the EPA. The average American eats about one-half of a cup of cooked rice per day, while consumption among Asian Americans exceeds two cups per day, the researchers said.

This has raised concern and researchers are calling on the Food and Drug Administration to regulate the amount of allowable arsenic in rice. The researchers did not measure the actual arsenic levels of the rice consumed and are not making any dietary recommendations. But they say the results highlight the need for monitoring and regulation of arsenic levels in rice.

Arsenic occurs naturally in soil worldwide. While most other crops do not absorb it, rice does. Rice is grown in flooded fields which “dramatically changes the [soil] chemistry,” releasing arsenic locked up in soil minerals so it can be taken up by the rice, says Andrew Meharg, a professor of biogeochemisty at the University of Aberdeen in Scotland. For people in the United States and Europe, rice is the largest dietary source of inorganic arsenic, said Meharg.

The findings come shortly after the release of test results by Consumer Reports showing potentially unsafe levels of arsenic in apple juice. The results also cited concerns over arsenic levels in rice, particularly the rice in infant cereals. Chronic exposure to low levels of inorganic arsenic has been linked to increased risks of bladder, lung and skin cancer, as well as Type 2 diabetes and cardiovascular disease, according to the Environmental Protection Agency.

Still, previous studies have found most arsenic in rice eaten in the United States is in the organic form, said Christopher States, a toxicologist at the University of Louisville in Kentucky who was not involved in the study. Because of this, the arsenic consumed in half a cup of rice suggested by this study “is not considered a hazardous level for an adult exposure,” States said. However, it's still possible that exposure to these levels could contribute to disease, States said. “We really do not know what a truly "safe" level is,” States said.

“[It's] too simplistic to say that all organic arsenic is safe,” said Carolyn Murray, an assistant professor of community and family medicine at Dartmouth Medical School. Research done in the late 1990s showed that high amounts of organic arsenic caused cancer in rats, the new study points out.

Exposures to arsenic early in life, as in the prenatal period, are probably more important because this is when humans are particularly vulnerable to disease development, States said. “These early life exposures may be the prime drivers of cancer,” he said.

Stacy Fitzgerald-Redd with the USA Rice Federation, a rice industry trade group, says “there's never been a study that showed that arsenic levels in rice were at a level where consumers should be concerned, or where there would be any cause to panic.”

Fitzgerald-Redd points out that if there were a problem with rice, it would have become clear in Asia, where people typically eat 200 pounds of rice a year, compared with just 25 pounds a year in the USA. “There has never been a definitive study that suggests that rice consumption either in the U.S. or parts of Asia has led to adverse health effects,” she says.

Still, the Rice Federation welcomes FDA scrutiny of rice. “It's always good to know that FDA is looking into the safety of our food and the rice industry certainly supports that effort.”