Infant rice cereal and rice snacks contain some arsenic, and babies who eat these products have higher levels of arsenic in their urine, a study shows.

It's not clear yet whether the arsenic will affect their health down the line.

"We knew rice cereal was a typical first food for babies - but we knew very little about how common it is to feed infants rice cereal in the U.S., or about the timing of introduction of rice cereal," said lead author Margaret Karagas, of the Geisel School of Medicine at Dartmouth College in Hanover, New Hampshire.

Rice grains can take up arsenic from their environment, and U.S. rice has some of the highest arsenic concentrations in the world, she said.

"Arsenic is a known carcinogen that can influence risk of cardiovascular, immune and other diseases," Karagas told Reuters Health by email. "There's a growing body of evidence that even relatively low levels of exposure may have adverse health impacts on young children including on growth, immunity and neurodevelopment."

She and her team are still investigating whether the infants in this study had any health effects due to arsenic exposure, she said.

The researchers studied 759 infants born to mothers age 18 to 45. Parents reported their infant's intake of rice products like rice cakes or puffs or dried breakfast cereals containing rice, or brands of cereal bars sweetened with brown rice syrup, in interviews when the baby was four, eight and 12 months of age. The researchers also collected infant urine samples to test for arsenic levels.

About 80 percent of the children were introduced to rice cereal before age one, and a third were eating rice snacks by their first birthday.

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Among kids who did not eat fish or seafood, urinary arsenic concentrations were higher for those who ate infant rice cereal or snacks than for those who did not, according to results in JAMA Pediatrics.

The researchers also tested for arsenic levels in some of the more commonly reported rice snacks.

"We were surprised by the percentage of infants who ate rice snacks and that one of these products contained levels above the current E.U. standard of 100 parts per billion," Karagas said. "This was a strawberry flavored puffed rice snack, which contained 40 percent inorganic arsenic, with the first two ingredients listed as brown and white rice flour."

Inorganic arsenic exposure has been linked to cancer as well as other health problems such as neurological, cardiovascular, respiratory and metabolic diseases, said Dr. Antonio J. Signes-Pastor, of the Institute for Global Food Security at Queen's University Belfast in Northern Ireland.

"This is of particular concern for young children, who are more sensitive to adverse health effects of inorganic arsenic and consume higher amount of inorganic arsenic from food compared to adults per kilogram of body weight," said Signes-Pastor, who was not part of the new study.

It is important, he said in an email, "to reduce exposure by establishing maximum limits of inorganic arsenic in rice and rice-based products."

The U.S. Food and Drug Administration had proposed a limit for inorganic arsenic in infant rice cereal of 100 parts per billion, which would mimic the current limit in the European Union, Karagas said.