A study analyzed more than 200 samples of roughly 60 rice products -- from bulk rice to baby foods to instant cereals -- and found that nearly all them contained a form of arsenic that’s known to cause bladder, lung and skin cancers. (Carolyn Kaster/ASSOCIATED PRESS)

The Food and Drug Administration plans to announce Wednesday that it is working toward a proposal that would limit the amount of arsenic in rice, a staple of the American diet that has long been identified as a leading dietary source of the toxin.

The announcement is set to coincide with the release of a Consumer Reports study that analyzed more than 200 samples of roughly 60 rice products — from bulk rice to baby foods to instant cereals — and found that nearly all of them contained the “in­organic” form of arsenic that’s known to cause bladder, lung and skin cancers.

The FDA said its testing of rice products yielded similar results. But while Consumer Reports recommends that consumers reduce their rice consumption for now, the FDA does not advise a change in eating habits. It plans to test 1,000 rice samples in addition to the 200 it has already analyzed before making a recommendation late next year.

“It’s a priority for us to complete the analysis to decide what levels to set and what other steps to take,” said Mike Taylor, the FDA’s deputy commissioner for foods. “We’re not prepared, based on preliminary data, to advise people to change their eating patterns.”

The government limits the amount of arsenic in drinking water, but virtually no standards exist for arsenic in foods. For years, consumer advocates have urged regulators to take action, singling out rice in particular, which consistently ranks as a top arsenic-containing food in a growing body of research. The Illinois attorney general’s office joined the fray this week, urging the FDA to limit the inorganic arsenic in infant rice cereals.

Arsenic is a naturally occurring chemical element in soil and water that’s picked up in trace amounts by all plants, not just rice, as the USA Rice Federation often notes. The industry group said it is unaware of any arsenic-related illnesses that have been linked to eating U.S. rice. It also says that rice is a wholesome grain with nutritional benefits that far outweigh any perceived risk from arsenic.

Tips: Reducing your arsenic risk with rice products

Jim Coughlin, a toxicologist who is working with the industry, said arsenic is such a “famous poison” that its mere mention alarms people. But rice is so safe that it is one of the first foods fed to infants, in part because it is less allergenic than other grains, he said.

“You can never get arsenic to zero when it comes to foods grown in soil,” Coughlin said. “There are things you can do to try and reduce the contamination. But a plant will pick up trace amounts of arsenic and lead and cadmium from the soil because it can’t distinguish between the metals we’d rather not have and the metals that are essential to its growth.”

But not all foods pick up arsenic equally, said Urvashi Rangan, a director of Consumer Reports and a toxicologist. And just because arsenic is naturally occuring, that does not mean it is safe, she said. The rice plant — whether it is grown using organic or conventional methods — is especially prone to picking up arsenic because it usually grows under water, sucking up arsenic from the water above and the soil below, she said.

The Consumer Reports study found that within every brand tested, the average inorganic arsenic found in brown rice was consistently higher than in white rice. That’s because arsenic collects in the dark-brown outer layer of rice grains, which are stripped when the grains are polished to produce white rice. But across brands, brown rice sometimes had lower levels of the arsenic than white, depending on where it was grown.

The report also found that the highest levels of inorganic arsenic were in white rice grown in Arkansas, Louisiana, Missouri and Texas — which collectively produce about three-quarters of the nation’s white-rice supply. Residues of arsenical pesticides once used to treat the region’s cotton crops may be to blame, the report said.

Scientists measure arsenic in “parts per billion,” a unit so small that one part per billion is equal to a single drop of water in an Olympic-size pool, the rice industry said. While the amounts sound miniscule, they add up over a lifetime, Rangan said. The FDA also said it is concerned about the cumulative effect of inorganic arsenic.

To provide context for the test results, Consumer Reports focused on the federal standards for drinking water — 10 parts per billion. A quarter-cup dry serving of some of the rices tested could expose an adult to more than 50 percent of the inorganic arsenic he or she would get by guzzling a liter of water, at the federal limit, in a day. But the FDA and Consumer Reports said their testing showed a lot of variability within samples of the same product and within categories of foods, which is why the agency wants to do a more thorough risk assessment.

Rangan said the results of her study are meant to offer a snapshot of the arsenic levels, not conclusions about the safety of any particular brand. “It’s meant to give consumers guidance for moderating their consumption while the government considers the steps it might take to reduce the levels of arsenic in rice,” she said.