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.)

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.

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

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.

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.

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.

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.

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

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.

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 sea spray.

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

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.

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.

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

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

Ultraprocessed foods include preservatives, dyes, sweeteners, and more

Processed foods are those that have been altered from their original state, which includes numerous processes that we consider natural, such as cooking or salting. Ultraprocessed foods contain at least one item that wouldn’t be found in a kitchen, like hydrogenated oils or high-fructose corn syrup. It’s estimated that nearly 75% of all foods consumed in the US are ultraprocessed, though that doesn’t mean that all of them are unhealthy. In fact, some, such as prepackaged whole wheat bread and soy milk, are recognized for their health benefits.

Microplastics are infiltrating the human body with unclear but concerning effects

Scientists have linked microplastics to immune system damage, hormone disruption, inflammatory diseases, and even cancer—yet most of their health impacts remain unknown due to limited research. Studies suggest we ingest about a credit card's worth of plastic weekly.

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).

Research shows that microplastics and nanoplastics can accumulate in major arteries, and patients with these deposits are significantly more likely to suffer heart attacks, strokes, or death.

The amount of plastic chemicals in 300 everyday Bay Area foods

Food production is more complicated than it appears, and manufacturing, packaging, and shipping processes can add significant substances to your food. This massive project compiled data on 300 samples of foods delivered to the San Francisco area, testing for the presence of 18 different kind of plastic. Learn how to read the data here with its helpful guides and then explore the table yourself.

Nanoplastics can bypass the blood-brain barrier and may harm the nervous system

Nanoplastics are formed from the breakdown of microplastics and can breach cells. Their large surface area relative to size allows them to carry higher concentrations of forever chemicals than the surrounding environment into sensitive organs.

As of 2025, the FDA states that microplastics have not yet been shown to pose a risk to human health, though it acknowledges that evidence suggests microplastics and nanoplastics have entered the food supply.

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

Why processed foods can be so addictive

In recent years, many critics have voiced their concerns about the food industry and how ultra-processed foods affect our health. Despite our awareness of these issues, processed foods are still incredibly hard to remove from our diet. In this podcast by The Guardian, Dr. Chris van Tulleken explains how “junk food” is created to get us hooked, how it negatively affects us, and what we can do to improve our eating habits.

Ultra-processed foods are made to maximize cravings and encourage overeating

Often disguised as healthy options like granola bars and low-fat yogurt, these foods silently fuel chronic diseases, despite dominating diets. Reviewing labels for ingredients like stabilizers and emulsifiers can serve as indicators to help identify these products.

Scientists have found that sewage sludge used as fertilizer introduces various microplastics into soil, which persist in farmland for decades.

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.

Ultraprocessed foods are linked with a 58% elevated risk of developing dementia.

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.

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.

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.

Microplastics 101: What we know about the contaminants invading our bodies

Fifty-one trillion particles of microplastics float in our oceans. Yet there is very little science of how this affects our health. This quick 2-minute video explains the dangers of microplastics.

Microplastics have been identified across human body systems, with research finding they are most commonly ingested through inhalation, drinking water, and diet before crossing barriers into organs.

Microplastics have been found across all of Earth's depths and altitudes, from plastic debris in the Mariana Trench to fragments found in snow samples near the summit of Mount Everest.

Learn the history of food science breakthroughs from the 20th century

Long after humans developed the means to produce sufficient food to feed civilizations, scientific research focused on a wide variety of objectives, such as developing methods to preserve food quality (accomplished via frozen food), speeding up cooking (leading to the microwave), and lowering the cost of sweetening food, which high fructose corn syrup provides.

The prevalence of microplastics came from plastic’s affordability and versatility

Microplastics' durability and overuse have led to massive pollution that overwhelms the planet's ecosystems. Avian, terrestrial, and marine life have been observed to contain microplastics in their bodies, but reverting to paper, cotton, and other materials in manufacturing also brings environmental challenges.

World War II helped convince food companies to produce more processed foods

Processed foods had existed since the 19th century, but they began infiltrating the mainstream during World War II, with foods designed to last on the battlefield for days. After the war, food companies saw great potential in the relatively cheap foods aimed at busy households. (Some readers may experience a paywall.)

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.

Explore how close you live to some of the most contaminated places in the US

Known as Superfund sites, these toxic locations undergo long-term cleanup to remove hazardous waste, protect health, and restore land for safe reuse. As of 2025, the EPA lists around 1,300 active Superfund sites on its National Priorities List, with more than 450 cleaned and removed since 1980.