Both studies show relatively similar levels of arsenic in rice. The FDA's analysis, including 200 samples, showed average levels of 3.5 to 6.7 micrograms of inorganic arsenic per serving. Consumer Reports, with 223 samples, found levels up to 8.7 micrograms. A microgram is one billionth of a kilogram.
It is almost impossible to say how dangerous these levels are without a benchmark from the federal government. Consumer Reports uses New Jersey's drinking water standard — a maximum of 5 micrograms in a liter of water — as comparison because it is one of the strictest in the country. But it is unclear how accurate it is to compare arsenic levels in water and arsenic levels in rice — most people consume more water than rice, so drinking water standards may need to be tougher.
It is because of this uncertainty that consumer groups have urged the FDA to set a standard.
Urvashi Rangan of Consumer Reports says the group is not trying to alarm rice eaters and parents feeding their children rice, but to educate them so they can diversify their diets. Consumers should be more protected since arsenic is a known carcinogen, she said.
"It doesn't make sense not to have standards for rice," she said.
The Consumer Reports study found higher levels of arsenic in brown rice than white rice, a result of how the two different types are processed. It also found higher levels in rice produced in southern U.S. states than in rice from California or Asia.
Rice growers jumped on the report. A statement from the industry group USA Rice Federation said that U.S. rice growers do not use arsenical pesticides.
"We understand that 'arsenic' is an alarming word, but we believe it is important for consumers to know that arsenic is a naturally occurring element in our air, water, rocks and soil," the group said in a statement. "This is how plants uptake arsenic. As a result, it's always been in the food supply and is in many healthy foods that are consumed by billions of people every day."