Researchers call for monitoring of arsenic levels in rice

henry

It's long been known that rice takes up more arsenic from soil than other crops, and now a new study is raising concerns about the arsenic levels 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 USA. But the Environmental Protection Agency has set arsenic limits in water of 10 parts per billion. Researchers in a paper in Monday's Proceedings of the National Acaemy of Sciences 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 findings are worrisome enough that researchers are calling on the Food and Drug Administration to regulate the amount of allowable arsenic in rice.
The scientists initially were looking at arsenic exposure from unregulated well water in New Hampshire, where 40% of the state's population gets its water from wells, says Margaret Karagas, a professor at Dartmouth Medical School in Lebanon, N.H.
The researchers looked at pregnant women. Very high-dose exposure to arsenic in places like Bangladesh has been related to infant mortality and low birth weight, but effects at levels more typical of the USA are not known.
They measured how much arsenic the women excreted in their urine and because "diet is the main source of arsenic exposure for Americans," the scientists also had the women record their rice and seafood consumption, Karaga says.
As expected, they found that women whose water came from wells had higher urinary levels of arsenic. But they also found that "women who reported eating rice in the two days before the urine was collected had higher arsenic levels," Karagas says.
The researchers did not measure the actual arsenic levels of the rice consumed, and are not making any dietary recommendations. However, they say the results highlight the need for monitoring and regulation of arsenic levels in rice.
Arsenic occurs naturally in soil worldwide. Most crops don't take it up. But 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 Andy Meharg, a professor of biogeochemisty at the University of Aberdeen in Scotland. The amount of arsenic in rice can further be affected by local conditions. In the USA, California rice has lower arsenic levels than rice from Texas and Arkansas, he says.
Arsenic in rice, and food in general, can come in either organic or inorganic form. Organic arsenic is a Class One human carcinogen. The dangers of inorganic are still being studied, says Meharg.
This can be a problem for people with celiac disease, who cannot tolerate the gluten found in wheat and therefore eat many items made of rice. Also for those who consume large quantifies of rice milk, he says.
Some varieties of rice take up less arsenic than others. Meharg will be publishing a paper looking at arsenic and rice varieties worldwide early in 2012, he says.
There aren't currently good studies to show whether higher arsenic exposure through rice consumption has any health effects, says Meharg.
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."