One chemical, many foods

Taking a more pragmatic approach are food scientists. They say that acrylamide has been discovered in many foods -- black olives, coffee, bread, breakfast cereal -- and that humans have been eating the chemical for years with few, if any, ill effects.

As the two sides square off, two questions frame their debate: At what level does acrylamide pose a threat to humans? And how much risk is acceptable?

Though acrylamide has long been recognized as a rodent carcinogen and human neurotoxin, no one ever suspected to find it in food. It was believed to be the exclusive product of industrial waste.

Then came the discovery in 2002 that acrylamide is almost everywhere in our diet. The tasteless, invisible byproduct of cooking is formed when foods -- particularly high-carbohydrate foods such as potatoes -- are fried or baked at high temperatures.

Acrylamide turns up in a wide variety of foods; the chemical is present in 40% of our daily calories. But French fries and potato chips contain the highest concentrations, and because Americans consume so much of them, acrylamide fears have focused around these products.

The chemical's sheer ubiquity has led some scientists to question the California attorney general's rationale in filing suit in August against McDonald's, Wendy's, Burger King, KFC and several potato chip manufacturers, including Cape Cod Potato Chips and Kettle Foods.

The suit says the companies are required, under California's Proposition 65, to warn the public that their potato chips and French fries contain a toxic chemical.

Many scientists -- including the author of the only published epidemiological studies on acrylamide -- argue that there simply isn't enough data to justify a warning.

"I think a lot of people were pretty surprised" at the lawsuit, says Lorelei Mucci, a researcher at Harvard University's School of Public Health and lead author of two published epidemiological studies on acrylamide. "It's prevalent in so many foods that to just target these manufacturers is not fair."

Mucci's studies suggest that the amount of acrylamide consumed through diet is insufficient to raise the risk for colon, rectal, kidney, bladder and breast cancers, all cancers caused in high-dose acrylamide testing on laboratory animals.