The chemical, perfluorooctanoic acid, is associated with the manufacture and use of Teflon and other moisture-resistant products. It is commonly known as PFOA.

Tim Begley, a research chemist at the Food and Drug Administration, reported in 2005 that PFOA and similar substances used in paper products in which such food as pizza and popcorn are sold tend to migrate into food when the paper is heated.

Microwave popcorn bags release several hundred times as much of the chemicals as does cookware that has been coated with substances like Teflon, Begley reported.

In a follow-up study reported this month, Begley confirmed his earlier findings and produced data that raises questions about whether FDA is underestimating the amount of the chemicals that get into food.

Deirdre Flynn, executive director of the Popcorn Institute, said in a telephone interview that "the (popcorn) industry has worked hard to produce a safe and quality product for consumers to enjoy."

"FDA and the industry have always worked together to ensure continued safety," she added.

Dan Turner, a spokesman for DuPont, which uses PFOA in the production of Teflon, said the company is convinced its products pose no threat to human health.

"DuPont believes and maintains that consumer products sold with trace levels of PFOA are safe for their intended use," he said in a telephone interview. He added that he was familiar with the Johns Hopkins research.

"To date, there are no known human health effects known to be caused by PFOA," he said.

Evidence of PFOA's presence in 100 percent of fetal cord blood samples analyzed by CDC and Johns Hopkins University toxicologists was reported last month.

The concentrations were low, the researchers said, and both the Environmental Protection Agency and the Food and Drug Administration have said they know of no evidence that the American public is being exposed to dangerous levels.

However, the Johns Hopkins toxicologist who directed the study has said it also revealed statistically significant links between levels of PFOA in cord blood and the babies' birth weight, head circumference and other common measurements of newborn health.

The report is among a rash of studies that in the past few months have heightened concerns about the presence of PFOA and several related chemicals in human beings, their food and the environment.

An EPA panel of scientific advisers told administrator Stephen Johnson last year that most of them were convinced that PFOA should be regarded as a likely human carcinogen and regulated accordingly. Some felt it should be designated a "possible" carcinogen.

The panel did not offer advice on the levels of exposure that might cause cancer in humans but noted that in animal experiments, the chemical was associated with liver and pancreatic cancers.

PFOA and its chemical cousins are man-made substances that since the 1950s have become ubiquitous in the environment, from the Arctic Ocean to the soils of rural Georgia.

The substances have been found in the blood of giant pandas in China, albatrosses on the Midway Atoll in the middle of the Pacific Ocean, bottlenose dolphins in Indian River Lagoon, Fla. and polar bears in Greenland.

John Washington, a research chemist at the EPA laboratory in Athens, Ga., reported last month that "trace amounts" of PFOA were extracted from soil samples collected at Athens and near Watkinsville, Ga.