The World Health Organization urged further research.

"It is clear that acrylamide is a problem," FDA Deputy Commissioner Lester Crawford said in an interview. "It doesn't need to be in food."

But no one knows whether acrylamide causes cancer in people, and, if so, what amounts are dangerous, what foods it is in or whether it can be removed.

The FDA is testing baby food, canned beans, cereals, chocolates, cookies, crackers, french fries, infant formulas, nuts, nut butters, potato chips, meat and other foods, Dr. Lauren Posnick of the FDA's Center for Food Safety and Nutrition said at a public meeting.

She said her team had sampled 150 of 600 different foods the FDA plans to test.

French fries and potato chips had a varying amount of acrylamides, some with a high amount. Some crackers and nuts also did, but most foods - including infant formulas - contained very low levels of acrylamides or none at all.

ACRYLAMIDES DAMAGE DNA

Other FDA researchers said they had done tests on acrylamides and found they damage DNA and cell proteins. Such damage is often a first step to cancer because it can lead to mutations that cause cells to grow into tumors.

"It is the fact that acrylamide ... attaches to DNA that is of concern to us," said Dr. Bernard Schwetz, the FDA's senior adviser for science.

Acrylamide, used to purify water and for other industrial processes, can cause cancer in laboratory animals but has never been linked to human cancer.

Schwetz noted that not all the animal studies duplicated how humans become exposed to acrylamides. For instance, the chemical was injected directly into rats for one study.

Food is known to carry cancer-causing agents. For example, barbecuing or grilling foods can form compounds called PAHs, which can cause cancer, and now the federal government advises Americans to grill foods carefully to avoid burning them.

"The fact that a chemical that has carcinogenic properties in laboratory animals in food is not a new finding," Schwetz said. "The presence of acrylamides in food isn't something that just happened in the past several months."

Schwetz said the FDA is working to find out how acrylamides are formed, whether changing cooking oils will lower their occurrence and whether people absorb them when they eat them - or if the chemicals simply pass through the body.

One possible precursor is aspargine, a common amino acid.

Two teams of scientists reported this week that they had found amino acids, including aspargine, react with sugar at high temperatures.

Richard Stadler at the Nestle Research Center in Lausanne, Switzerland, and Donald Mottram at Britain's University of Reading said they had found a chemical process called the Maillard reaction could explain how acrylamides form in food.

Writing in Thursday's issue of the science journal Nature, they said they had found asparagine has the potential to become an acrylamide in the Maillard reaction. Asparagine is particularly abundant in potatoes and some cereals.

One important question is how much of the chemical people actually eat.

Thomas Sinks of the U.S. Centers for Disease Control and Prevention said his agency will add a test for acrylamide to its annual survey of what chemicals Americans are exposed to. The CDC screens thousands of Americans to see what chemicals are in their blood and urine.

In the meantime, the FDA sticks to the standard government advice to eat a balanced diet, with plenty of fruits and vegetables and only the occasional fried food.

Food processors said they would cooperate with the FDA.