Scientists and regulators are raising concerns about the potential health and environmental effects of an important family of industrial chemicals.

Those concerns were highlighted yesterday when the Environment Protection Agency announced it was forcing the chemical industry to do further research on perfluorooctanoic acid, or PFOA, one member of that family.

The broader group of chemicals, known as perfluorinated acids, has been discovered widely in the environment and in almost all Americans. No human health effects have been discovered, but E.P.A. officials’ concerns were raised by recent toxicological data in animals.

Since World War II, perfluorinated acids have become incorporated into many brand-name chemicals because they repel water and oil and are resistant to heat and chemical stress. Used in the manufacturing process of Teflon and Gore-Tex, they are released as breakdown products from Stainmaster, Teflon and the original formulation of Scotchgard. They are also used to make polymers for aircraft and electronics.

Scientists say the properties that make the chemicals attractive to industry — their chemical stability and resistance to high temperatures — may potentially have serious effects on the environment.

Perfluorinated acids do not degrade. They are widely distributed — showing up in the Arctic, in food samples and in almost all human blood samples that have been tested. No one has found that the chemicals have a toxic effect on humans, but early research on animals shows that at least some perfluorinated acids in high doses have the potential to be toxic.

This combination of traits caught the attention of the E.P.A.

“Though we have concerns, there is a lot of uncertainty,” said Stephen L. Johnson, assistant administrator of E.P.A.’s Office of Prevention, Pesticides, and Toxic Substances. “Given the uncertainty, additional scientific information is needed to determine if regulatory actions are necessary.”

Environment groups are comparing perfluorinated acids to PCB’s and DDT, which appeared benign when they were first introduced. Environmental groups note that PCB’s were banned by Congress in 1976, and less was known about them then than is currently known about perfluorinated acids.

Chlorofluorocarbons, or CFC’s, were also prized for their chemical stability until the 1970’s, when scientists discovered that their accumulation in the atmosphere eroded the ozone layer.

Relatively little is known about perfluorinated acids — where they are coming from, how they travel, how they get in the human body or their long-term health effects.

“We don’t have the data to do more at this point than to worry,” said Dr. Gina Solomon, a physician with the Natural Resources Defense Council. “All we can do is predict that the chemical characteristics can add up to a problem.”

But 3M, which stopped producing chemicals related to perfluorinated acids in 2000, has concluded after extensive studies that humans are not at risk. “The bottom line is that at the very low levels that we find in human serum, there are no health effects associated with those very low levels,” said Dr. Larry Zoebel, 3M’s medical director.

To date, most research on persistent organic chemicals has focused on those containing chlorine, like PCB’s and CFC’s, even though scientist knew that fluorinated compounds were also persistent and accumulated in organisms.

Scientists assumed that because the bulk of fluorinated compounds were incorporated into polymers they would not spread widely in the environment. This assumption unraveled after more sophisticated technology to detect minute quantities of fluorinated chemicals became available in the late 1990’s.

The discovery of the widespread presence of the chemicals has surprised scientists and regulators, leaving them scrambling to learn more. “Polar bears and eagles certainly don’t buy our products,” Dr. Zoebel said.

The properties of perfluorinated acids stem from the carbon-fluorine bond, one of the strongest in chemistry. Perfluorinated, or “fully fluorinated,” compounds are ones in which fluorine atoms have replaced all the hydrogen atoms in the carbon-hydrogen bonds that are characteristic of organic molecules.

The perfluorinated acids are challenging traditional presumptions of how chemicals can move and behave, both in the environment and in organisms.

“It’s nonvolatile. It’s not soluble. How does it get to these remote locations?” asked John Giesy, a researcher at Michigan State who did much of the early research on perfluorinated acids for 3M.

In studies released in 2001, 3M reported finding one type of perfluorinated acid in various food sources: green beans from Mobile, Ala.; a loaf of bread from Pensacola, Fla.; and in two out of three ground beef samples from Port St. Lucie, Fla. The acids have also been detected in water in some parts of the country. Some people near Parkersburg, W.Va., have filed a class action suit against DuPont, objecting to the presence of one perfluorinated acid in their water.

Studies have found perfluorinated acids in almost all blood samples taken from the Red Cross across the country. But scientists do not know whether the chemicals are getting into people directly, or if they are the breakdown products as human metabolize other chemicals from the environment.

Unlike DDT and PCB’s, which increase in concentration by factors of millions in moving up the food chain, the perfluorinated acid concentration in organisms does not seem to differ as much from one species to another. Concentration also does not differ significantly from children to adults to the elderly, men to women. Unlike DDT, which accumulates in fat cells, the acids accumulate in the blood.

Perfluorinated acids, however, are more persistent than DDT or PCB’s, which break down over decades. Scientists say they have been unable to measure how fast perfluorinated acids degrade. “We don’t know if it does degrade,” said Dr. Scott A. Mabury, a researcher at the University of Toronto who has examined the chemicals.

Scientists have not been able to break the acids apart with high temperatures and strong acids that are found in the environment. “It redefines persistent as we normally use the term,” Dr. Mabury said.

Two years ago, the EPA became alarmed by 3M’s internal scientific studies on perfluorooctane sulfonate, known as PFOS, including one that resulted in the deaths of all the rat offspring within four days, a striking result for a toxicology experiment. E.P.A. regulators pressured 3M to stop producing PFOS. The company went one step further and dropped production of all PFOS-related chemicals, which represented some $300 million in sales, or 2 percent of the company’s revenue.

That unusual corporate decision caught the attention of scientists. Researchers began following up on 3M’s studies. Since then, top E.P.A. officials have turned their attention to PFOA, which was made by 3M and is now manufactured by DuPont in a North Carolina plant under the name C-8 and is used to make Teflon.

According to a risk assessment by the E.P.A., the estimated range of exposure for human beings, based on rat studies, overlapped with what the E.P.A. deemed unacceptable for toxic substances.

“What the E.P.A. is doing right now is a pretty brave thing,” said Kris Thayer, a senior scientist with the Environmental Working Group, an advocacy group that has put together a searchable database of documents drawn from E.P.A. and the West Virginia lawsuit (www.ewg .org/reports/pfcworld). “The bigger question is, How did we get here? How come after 50 years, it’s only now they are doing the toxicology studies?”

Environmental groups are concerned because internal studies done by the companies have shown that rats have experienced damage to the immune system, brain, pituitary gland, thyroid and sex glands when treated with perfluorinated acids. Limited studies with monkeys have also shown adrenal damage, liver damage, pancreatic damage, lung damage, decreased thyroid hormone levels and, in some cases, death.

But industry researchers at 3M and DuPont maintain that animals are exposed to levels thousands higher than the general population will ever realistically face.

“You have designed those studies to produce an effect,” said Dr. Robert Rickard, director of DuPont’s Haskell Laboratory for Health and Environmental Sciences, speaking on the studies on PFOA.

Some scientists say that the amount of some perfluorinated acids that is turning up exceeds what is being released from known manufacturing processes.

One study published in Nature that showed a number of detectable perfluorinated acids were released from overheating a chemical that is used as a nonstick coating that is similar to Teflon. (DuPont says that company evaluations have shown no PFOA is being released from Teflon at temperatures people would normally encounter in their kitchens.)

But Dr. David A. Ellis, an author of the study, noted that most people were not overheating pots on remote desert islands. Scientists conclude that the chemicals must be coming from somewhere else.

“If you can measure concentrations in the Arctic, then masswise, it has to be a consumer product which is huge and volatile,” said Dr. Ellis, a chemist at the University of Toronto.

One leading candidate is fluorotelomer alcohols, which are found in a wide range of household consumer products hair like shampoo, rug cleaners and food paper products. Unlike perfluorinated acids, fluorotelomer alcohols are volatile, so they can be carried long distances with air currents.

The E.P.A. is requiring the chemical industry to conduct more research on the relationship between perfluorinated acids and fluorotelomer alcohols, as well as provide information as to where and how much the alcohols are used.

“It’s a big Sherlock Holmes mystery right now,” Dr. Ellis said. “We are just trying to piece it all together.”