Teflon was an accidental discovery by a DuPont scientist in the 1930s resulting from efforts to create a safe refrigerant.

Used since the 1940s, 'forever chemicals' include thousands of different types of substances routinely integrated into industry and consumer products, yet research suggests they can accumulate in the body over time.

Watch 'Last Week Tonight' explore the risks of 'forever chemicals,' a group of human-made chemicals used in everyday products to make them resistant to water, stains, grease, and heat. (Warning: language.)

Per- and polyfluoroalkyl substances (PFAS) are a group of human-made chemicals used in a wide range of products due to their unique properties. However, because they can persist in the body and environment for thousands of years, they've earned the moniker "forever chemicals"—and have been linked with numerous health risks.

Forever chemicals are so common that experts concluded in 2022 that it's uncertain whether limiting consumer exposure would truly reduce one's exposure to these substances, and noted it would still take years for the body to clear them.

Although PFAS, or forever chemicals, are intentionally designed to be extremely stable and long-lasting because of their strong carbon-fluorine bonds, these bonds can be broken by heat, plasma, and supercritical water.

Most of the 86,000 consumer chemicals registered with the US EPA have never received rigorous toxicity testing, though not all those are still in current use.

See this interactive global map that highlights which forever chemicals have been detected in specific wildlife species, providing data on hundreds of species exposed to these hard-to-breakdown substances.

Forever chemicals accumulate up the food web, with recent research indicating that apex predators have higher concentrations because they're eating prey that also have accumulated the substances.

Why bacterial bioremediation may help counter the negative effects of past chemical solutions

Molecules such as DDT, a synthetic insecticide, and PFAS—"forever" chemicals used to make products resistant to heat, water, and grease—have historically been used across various industries but are now known to be harmful. Microbes that can convert some of these substances into nontoxic products, such as water and carbon dioxide, have already been identified, with ongoing research to find others.

Explore this interactive EPA map, which shows 'forever chemical' testing results for public water systems—with brown spots indicating testing above national limits.

A remote Scottish island is awash in forever chemicals even though there are no obvious industrial sources nearby, and scientists suspect the toxic substances are accumulating via seaspray.

Listen to a reporter discuss his story spotlighting a decades-long corporate cover-up about forever chemicals, substances which can persist in the environment for hundreds of years—though not forever.

Fluorinated molecules are the most impactful, longest-lasting greenhouse gases

Developed as replacements for ozone-depleting substances in refrigeration and air conditioning systems, these compounds are released through leaks in and ongoing use of these appliances, as well as from various industrial processes. They can remain in the atmosphere for thousands of years and have warming potentials that are a thousand to tens of thousands of times greater than those of carbon dioxide.

Stainless steel and cast-iron pans should be used over older nonstick cookware

Although modern nonstick pans avoid forever chemicals like PFOA, they were previously used in the manufacturing of Teflon coatings and have been linked with certain types of cancer, infertility, and other adverse health outcomes. Vintage plastic utensils should also be avoided due to the leeching of contaminants in early formulations of plastic.

Cyanoacrylate, or superglue, was discovered by accident during World War II when researchers tried to create a clear plastic for precision gunsights.

Many chemicals used in fracking fluid have been classified as toxic

Although the fluid has been known to leach into drinking water supplies, raising health concerns, fracking is exempt from federal clean water regulations due to a loophole in the Energy Policy Act of 2005 championed by former US Vice President Dick Cheney.

Find fracking wells where you live and what chemicals operators are using

Fracturing fluid recipes are largely proprietary, but FracFocus has maintained a database of chemical disclosures since 2011. Today, the Department of Energy-affiliated nonprofit has more than 240,000 disclosures, along with a searchable database of fracking wells by state, county, and city.

BPA-free plastics may still pose health risks because they often contain other structurally similar chemicals.

How nylon was created

Nylon, one of the most ubiquitous materials in the world, was invented in 1935. Chemist Wallace Carothers was hired by American conglomerate DuPont to perform research. After seven years of work he produced nylon, the first wholly synthetic fabric. Carothers’ life ended tragically, but his contributions revolutionized everything from military equipment to women’s fashion.

The history of natural and synthetic plastics

From cheap toys to woolly jumpers, plastic can be found in more products than many people realize. From a chemist's perspective all these things are made of the same class of materials: Polymers. And the distinction between which ones we happen to call "plastics" and which ones we don't is fairly arbitrary.

The five most common chemicals found in modern food

Most modern processed foods rely on a number of preservatives to stay fresh from production to our plates. The most common include citric acid (preservative and flavor), sodium benzoate (preservative), xanthan gum (thickening and stabilizing), carrageenan (thickening), and red dyes 3 and 4 (for color).

Why helium helped preserve the US' founding documents, but was later replaced

In 1951, the Charters of Freedom were stored in glass and metal cases filled with helium, which would not chemically react with the documents. After microscopic cracks were identified in the glass through which helium could leak out of and—experts feared—pollutants could infiltrate, new encasements made of aluminum, titanium, and argon replaced the old system in 2003.

DNA may serve as a flame retardant by self-extinguishing some burning materials

When DNA burns, phosphate groups release phosphoric acid, and nitrogenous bases release ammonia. These molecules, along with the sugar in DNA's backbone, shift the combustion reaction toward the formation of intumescent char. This puffy, carbon-rich layer protects open flames from burning the material beneath.

Microplastics are entering human food chains through carrots, wheat, and other foodstuffs grown in farmlands fertilized by sewage sludge.

Japanese scientists have developed an eco-friendly plastic that naturally dissolves in hours, leaving behind molecules containing phosphorus and nitrogen, which fertilize soil.

Why a Montreal Protocol amendment cut back on the replacements for CFCs

Hydrofluorocarbons were introduced in the 1990s as ozone-safe substitutes for chlorofluorocarbons and hydrochlorofluorocarbons. However, scientists later found that they trap thousands of times more thermal energy in the atmosphere than carbon dioxide does, prompting a 2016 amendment to the Protocol to phase them out.

Learn about the seven types of plastic, including their recyclability, toxicity, health risks, and common uses.

How a government chemist founded the FDA—by poisoning people

The Poison Squad tells the story of government chemist Dr. Harvey Wiley who, determined to banish these dangerous substances from dinner tables, took on the powerful food manufacturers and their allies.

View a sample of objects surprisingly derived from crude oil, including chewing gum and lipstick

Crude oil processing produces a variety of fuels and the building blocks for plastics, but it also distills out the hydrocarbons used to make aspirin, Teflon, vinyl, crayons, candles, Tupperware, roofing shingles, asphalt pavement, hair dye, anesthetics, food-grade lubricants, polyester, synthetic rubber, and resins for items like dentures.

Volatile chemical contamination can last in burn areas long after urban wildfires

Lead, arsenic, asbestos, and other chemicals have been found trapped in smoke-exposed rugs, couches, pillows, and other furniture that appeared otherwise undamaged from the 2025 LA wildfires. The gradual release of these substances has produced dangerous indoor air concentrations and contributed to increased emergency room visits and abnormal blood tests.

Exploring carbon compound pore structures contributed to improved gas mask filtration

During World War II, the British Coal Utilisation Research Association sought to improve the efficiency of coal as an energy source and studied the effectiveness of charcoal filters to keep soldiers safe. Rosalind Franklin's research there formed the basis of her PhD and led to five scientific papers.

An overview of extremophiles and the biochemical adaptations employed by various types

These organisms thrive in environments that would normally be inhospitable to most living things by using molecules that help counter deadly environmental factors. These include antifreeze-like proteins that prevent psychrophiles from freezing and rupturing in polar regions, and osmoprotectants that prevent some extremophiles from losing water to salty environments.

Research shows that over 1,000 metric tons of microplastics fall on national parks every year—equivalent to 120 million bottles of water.

Why it's so hard to end the use of toxic lead

Lead was one of the earliest metals mined on Earth, desired for its soft malleability and used in cosmetics, pipework, gasoline, and more. But even though researchers demonstrated its toxicity in the 20th century, much of the world still uses it.

The theory of chemtrails originated from misinterpreting a US Air Force paper

The document proposed a future weather modification system to achieve military objectives, but clarified that such a system "does not reflect current military policy, practice, or capability." Past testing of biological and chemical weapons has accelerated conspiracies about streaks of condensation trailing aircraft to be harmful chemical agents.

Rising fracking rates have increased prices of some food products

Every fracking well uses approximately 20,000 pounds of guar gum, a thickening and stabilizing agent commonly used in ice cream, salad dressing, and baked goods. The polysaccharide is also a key component in some cosmetics and explosives.

The history of the Montreal Protocol, the only universally ratified treaty in UN history

Mario Molina and F. Sherwood Rowland discovered that chlorofluorocarbons released chlorine atoms that could break down molecules making up the protective ozone layer. Despite attempts to discredit scientists and economic concerns raised by politicians, the agreement to phase out ozone-depleting substances was signed in 1987.

Microplastics have been found everywhere there is liquid or vapor water, from the oceans and tropical waters to polar ice and the air we breathe, posing growing risks to wildlife and ecosystems.

Scientists still don't know why DEET is such an effective bug repellent

This chemical, used to keep ticks, fleas, mosquitoes, and other nuisance bugs away, is used by an estimated one-third of the US population and has been available to consumers since 1957. Researchers theorize that multiple mechanisms may be at work to deter bugs, including perhaps masking or confusing bugs' olfactory receptors.

Listen to how the 1902 'poison squad' experiments changed food safety in America

As part of government research, a group of young men were paid to eat standard American food—replete with food additives like borax and formaldehyde—which revealed the dangers of unregulated food. The work was led by the first FDA commissioner, Harvey Wiley, who helped end the "century of the great stomachache."