Bottlenose dolphins swimming in a South Carolina harbor, polar bears lumbering across Greenland’s ice sheets, and families inhabiting Ohio River Valley towns share a common secret: Their bodies contain high levels of industrial chemicals that most people have never heard of but are widely used in consumer products.

These perfluorinated compounds (PFCs) have been used to manufacture many microwave popcorn bags, carpets, fast-food wrappers, pizza boxes, camping gear, and cookware. While they are designed to make things nonstick, some of these compounds stick around in the environment—they are expected to last in nature for thousands of years.

On Friday, a statement signed by more than 200 scientists from 38 countries was published, documenting the threats PFCs may pose to human health and the environment. Traces of perfluorinated compounds are found in most places and people on the planet.

“We’ve laid out the current science on this very persistent and potentially harmful class of chemicals and provided a way forward to reduce their use,” says Arlene Blum, a Berkeley, California, chemist who advocates for safer chemicals and co-authored the statement, which was published in Environmental Health Perspectives.

Some Already Phased Out

First manufactured in the 1930s, PFCs are prized for their resistance to water and oils. DuPont and 3M used them to manufacture Teflon and Scotchgard.

Since 2001, U.S. companies have phased out some of the worst actors—the perfluorinated compounds with long chains of fluorinated carbon atoms that build up in tissues. As a result, in recent years, levels of these chemicals have dropped in people and wildlife.

But scientists in their new document, dubbed the Madrid Statement, say there is not enough information to know whether new PFCs in widespread use today are safer than the ones they are replacing. They called on governments to require manufacturers to conduct more extensive testing of new chemicals before bringing them to market and to develop nonfluorinated alternatives that aren’t toxic and don’t persist in the environment.

In a counterpoint to the statement also published in the journal on Friday, chemical manufacturers say that newer PFCs used now in consumer products are safer because they are made up of shorter chains of molecules that aren’t expected to build up in people and animals. “We believe that the Madrid Statement does not reflect a true consideration of the available data,” DuPont adds in a statement.

Jessica Bowman, executive director of the FluoroCouncil, a group representing the companies that make or use the compounds, says for many commercial uses, no suitable nonfluorinated alternatives exist.

“Fluorinated substances provide beneficial properties such as durability, strength, reduced flammability, and extreme weatherability,” she says. U.S. companies say they are working with China, India, and other countries that still use the older compounds to replace them with the newer, shorter-lived PFCs.

PFCs are used in firefighting foam and in wire insulation in airplanes, automobiles, and cell phones. “You probably couldn’t fly a plane or have a cell phone without fluoropolymers,” says DuPont representative Janet Smith.

In an accompanying editorial, the top environmental health official in the United States, Linda Birnbaum, director of the National Institute of Environmental Health Sciences, writes that “in the absence of indisputably safer alternatives,” society needs to have a discussion about tradeoffs.

“It’s what is convenient versus what is necessary. What uses of these chemicals are we willing to give up to keep these chemicals out of the environment and out of our bodies?” Birnbaum says in an interview with National Geographic.

“We Are All Exposed”

Nearly 100 percent of people tested in the United States have two phased-out PFCs—perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA)—in their blood. PFOS formerly was used to make Scotchgard, while PFOA was used to make Teflon, although little if any remained in cookware.

“One of the major concerns is that we are all exposed,” says Glenys Webster, an environmental health scientist at Simon Fraser University in British Columbia, Canada, who signed the statement.

Studies have shown that trace amounts of PFOA and PFOS may subtly alter human immune, hormonal, and nervous systems and could increase the risk of certain cancers.

Litigation over contamination of drinking water near a West Virginia DuPont chemical plant has led to major health findings. In a settlement with families, DuPont established an independent panel of scientists, which concluded that there is a “probable link” between PFOA in people who live there and high cholesterol, thyroid disease, kidney and testicular cancers, diabetes, and pregnancy-induced high blood pressure.

Air and water currents also carry PFCs to remote regions of the Arctic, where they have contaminated polar bears and other animals. Dolphins in the urban waters of Charleston Harbor and seals in San Francisco Bay have some of the highest levels of PFCs in the world.

It’s unclear whether the chemicals are harming the health of wildlife since few studies have been conducted. Research on dolphins, sea turtles, and otters suggest that PFOS, the major PFC found in the environment, may suppress immune systems. A recent study of polar bears found an association with altered brain chemistry.

“Animals act as a marker for what is going on in the environment,” says Duke University chemist Craig Butt. Butt says he agrees with the scientists’ statement but did not sign it because he thinks his efforts are best directed toward research, not activism.

Optimistic About Alternatives

Terry Collins, director of the Institute of Green Chemistry at Carnegie Mellon University, says that fluorinated chemicals have very particular properties difficult to reproduce in chemical coatings. But he is optimistic that new materials and technologies can be developed.