WASHINGTON (AP) — The Food and Drug Administration on Friday urged the food industry to reduce the already-tiny amount of arsenic found in baby rice cereals.

The agency proposed a new voluntary limit for the amount of inorganic arsenic — the type found in some pesticides and insecticides — in infant rice cereals to 100 parts per billion, equivalent to recommendations already in place in Europe. It's a very small amount, and around half of infant rice cereals the FDA sampled from retail stores in 2014 are already in compliance. But the FDA says the guidance is a precaution, as rice cereal is a leading source of arsenic exposure in infants.

"The proposed limit is a prudent and achievable step," said Susan Mayne of the FDA's Center for Food Safety and Applied Nutrition.

The FDA said parents don't need to stop feeding their infants rice cereal, but officials said they should vary rice with other things like baby oatmeal, barley and multigrain cereals that are also iron-fortified. The agency said rice intake is about three times greater for infants than adults relative to body weight, primarily due to infant rice cereal.

Gerber, the nation's largest manufacturer of baby rice cereal says it's already in compliance with the FDA's proposed arsenic levels.

"We have worked closely with our trusted rice supplier and their growers as well as researchers from agricultural universities to achieve some of the lowest levels of this element in U.S. grown rice," Gerber said in a release issued shortly after the agency's announcement.

Arsenic is naturally present in water, air, food and soil in two forms: organic and inorganic. Organic arsenic passes through the body quickly and is essentially harmless. Inorganic arsenic can be toxic and may pose a cancer risk if consumed at high levels or over a long period of time. Rice is thought to have arsenic in higher levels than most other foods because it is grown in water on the ground, optimal conditions for the contaminant to be absorbed.

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