Consumer Reports on Wednesday called on U.S. regulators to set limits for arsenic in rice after an investigation by the independent product testing group found "significant" levels of inorganic arsenic, a known human carcinogen, in some samples of popular rice products.

The watchdog group - whose other requests included a ban on the use of arsenic-containing drugs and pesticides used in crop and animal production - recommended that children and adults moderate their rice intake.

This is not the first time that the group has called on the U.S. Food and Drug Administration to take action on arsenic in the food supply. Earlier this year it called for limits on arsenic in apple and grape juices after similar testing found "worrisome" levels in those childhood staples.

Inorganic arsenic is deadly at high doses. It is a known carcinogen that has been linked to a variety of human cancers, including skin, lung and bladder, as well as heart disease and other illnesses.

Organic arsenic is believed to be far less harmful, but two organic forms measured - called DMA and MMA - are classified as possible carcinogens, Consumer Reports said.

Food is a major source of arsenic in the American diet. It can be found in fruits, vegetables, rice and seafood - all of which are considered healthy.

"The goal of our report is to inform - not alarm - consumers about the importance of reducing arsenic exposure," Urvashi Rangan, director of safety and sustainability at Consumer Reports, said.

"The silver lining in all of this is that it is possible to get a better handle on this" through improved farming and production practices, Rangan said.

The United States has established federal limits for arsenic in drinking water at 10 parts per billion (ppb). It is monitoring arsenic levels in some foods but has not set limits for arsenic in most foods.

Consumer Reports' rice tests included multiple samples of more than 60 products - including white and brown rice, infant rice cereals, rice crackers, rice pasta and rice drinks. The group said it found varying but measurable amounts of total arsenic - both inorganic and organic forms ─ in samples of almost every product tested.

Notably, testers found that one-fourth of a cup of uncooked rice from samples containing the highest inorganic arsenic levels would approach the amount of inorganic arsenic an adult would get from drinking one liter of water at the federal government's maximum limit of 10 parts per billion.

They also found that brown rice had higher levels of arsenic. That's because arsenic is concentrated in its healthy outer layers, which are removed to make white rice.

Products that raise particular concern for children - who are still developing and have significantly lower body weights than adults - include infant rice cereal, ready-to-eat cold breakfast cereals and rice milk, they said.

The scientists advised limiting servings of those products. In particular, they recommended not exceeding one serving of infant rice cereal per day and excluding rice milk from the daily diets of children under the age of 5.

As replacements, they suggested other healthy whole grains such as wheat, corn and oats, which have lower arsenic levels.

The rice industry calls reports on arsenic levels alarmist.

"Recent media stories based on studies about high levels of arsenic in rice are misleading the public about this issue, given that arsenic is everywhere and present in air, soil, water, and foods, including fruits and vegetables," the USA Rice Federation said on its website.

Nutritionist Julie Jones, speaking on a call hosted by the food industry-funded International Food Information Council Foundation on Tuesday, called the concern about arsenic in the U.S. food supply "misplaced" and said consumers should be more concerned about eating a healthy diet.

Jones added that certain elements of a good diet such as fiber can help reduce the harmful effects of arsenic.

Michael Harbut, a researcher and physician who treats people with arsenic poisoning, said the scientific data does not support such claims.

"There is no such thing as a safe level of arsenic," said Harbut, who leads the Barbara Ann Karmanos Cancer Institute's Environmental Cancer Program at Wayne State University in Detroit.