During the crucial early weeks of pregnancy, when fetal cells knit themselves into a brain and organs and fingers and lips, a steady flow of man-made chemicals pulses through the umbilical cord. Scientists once believed that the placenta filtered out most of these pollutants, but now they know that is not the case. Along with nutrients and oxygen, numerous synthetic substances travel to the womb, permeating the fetus’s blood and tissues. This is why, from their very first moments of life, every American newborn carries a slew of synthetic chemicals in their body.

Crucially, many of these chemicals have never been tested for safety. Of those that have, some are known to cause cancer or impede fetal development. Others alter the levels of hormones in the womb, causing subtle changes to a baby’s brain and organs that may not be apparent at birth but can lead to a wide variety of ailments, including cancer, heart disease, infertility, early puberty, reduced IQ, and neurological disorders such as ADHD. How did we end up in this situation, where every child is born pre-polluted? The answer lies in America’s fervor for the synthetic materials that, beginning in the mid-20th century, reshaped our entire society—and in the cunning methods that chemical makers used to ensure their untrammeled spread.

It began in 1934, when the munitions company DuPont was struggling to rescue its reputation. A new blockbuster book, Merchants of Death, argued that the company had unduly influenced America’s decision to enter World War I, then reaped exorbitant profits by supplying its products to America’s enemies and Allied forces alike. Meanwhile, a congressional probe had uncovered a bizarre plot—allegedly funded by DuPont and other companies that opposed the New Deal—to overthrow the U.S. government and install a Mussolini-style dictatorship. Almost overnight, DuPont became a national pariah.

In response, the company hired a legendary PR consultant who concluded that there was only one way DuPont could escape the controversy: by transforming itself in the public’s mind from a maker of deadly munitions into a source of marvelous inventions that benefited the general public. In 1938, the company debuted the first of these revolutionary materials: nylon, which could be spun into fibers “as strong as steel, as fine as the spider’s web,” a DuPont executive declared at the unveiling. The company’s wildly popular exhibit at the 1939 New York World’s Fair featured a shapely Miss Chemistry rising out of a test tube in a nylon evening gown and stockings. When nylon stockings went on sale in 1940, they sold out almost immediately.

But it wasn’t until World War II that synthetics really took off. Faced with shortages of natural materials such as steel and rubber, the U.S. government spent huge sums developing synthetic materials and expanding the assembly lines of chemical companies so that they could produce the quantities needed for global warfare. After the conflict, industry transformed these substances into a cornucopia of household goods. The plastic polyethylene, used to coat radar cable during the war, became Tupperware, Hula-Hoops, and grocery bags. An exotic new family of chemicals developed through the top-secret Manhattan Project showed up in products such as Scotchgard fabric protector. These substances, known to scientists as perfluoroalkyl and polyfluoroalkyl substances, or PFAS, gave ordinary goods uncanny resistance to grease, stains, water, and heat. They soon found their way into thousands of household items.

With the world suddenly awash in synthetics, people had access to a huge variety of low-cost goods—and this brought thousands of new chemicals into American homes. Most people didn’t give much thought to the implications. But manufacturers sponsored research on the health effects of the new substances they were using, much of it performed in the laboratory of Robert Kehoe, a toxicologist with a quasi-religious faith in the power of technological progress to solve society’s problems.

When I visited Kehoe’s archives at the University of Cincinnati, they were brimming with unpublished reports linking synthetic chemicals to a wide variety of health problems. Kehoe believed that the secrecy was justified. These chemicals, he argued in a 1963 essay that I found among his papers, would be desperately needed to “feed, clothe and house those who will populate this bountiful land in succeeding generations.” Given that the science was still developing, he wrote, focusing the public’s attention on the chemicals’ toxicity would be “neither wise nor kind.”

But by the 1950s, the emerging scientific consensus was that many man-made chemicals could disrupt key bodily functions, making them harmful at lower doses than ordinary poisons. A small but vocal group of activists began raising concerns about the lack of testing for chemicals in the food supply. They found an advocate in James Delaney, a Democratic congressman from New York, who formed a committee to investigate the issue. One of his lead witnesses was Wilhelm Hueper, a former DuPont pathologist who, according to his unpublished autobiography, had warned his employer of the link between synthetic chemicals and cancer as early as the ’30s. During his testimony, Hueper argued that because synthetic compounds could be damaging in minuscule doses and the effects were cumulative, no level of exposure to them could be presumed safe. He advised the lawmakers to require that chemicals in food be “tested for toxic and possibly carcinogenic properties,” and to ban those that cause cancer.

The titans of American industry had other ideas. Aided by the PR firm that would later pioneer Big Tobacco’s campaign to discredit the science on the harms of smoking, chemical companies lobbied lawmakers, hosted all-expenses-paid conferences for journalists, and placed pro-industry science materials in public-school classrooms, according to meetings minutes from the chemical industry’s main trade association. These efforts paid off. In 1958, when Congress passed a law requiring safety testing for chemicals that wound up in food, the thousands of substances already in use were presumed to be safe and grandfathered in.

One of those substances was Teflon, which is made with PFAS, or forever chemicals, as they are now known. According to correspondence in Kehoe’s files, DuPont had previously avoided marketing it for use in most consumer goods because of toxicity concerns. Workers who inhaled Teflon fumes developed flu-like symptoms. When scientists in Kehoe’s lab exposed dogs, guinea pigs, rabbits, and mice to the gases Teflon emitted when heated, many died within minutes, according to an unpublished 1954 report. But because Teflon’s ingredients had been grandfathered in, the company no longer needed to prove its safety to the government—only its benefits to customers. In 1959, it invited a reporter from Popular Science to its Wilmington, Delaware, headquarters for a pancake demonstration using a prototype Teflon pan. According to the magazine, the cakes came out nicely brown and left no crusty residue, “because the pan was lined with Teflon, a remarkable fluorocarbon plastic” that was “as slippery as ice on ice.” By 1962, DuPont-branded Happy Pans were flying off store shelves.

That same year, the naturalist Rachel Carson published Silent Spring, introducing the public to the disquieting idea that man-made chemicals were inundating people’s bodies. Most of the research Carson had drawn on wasn’t new. It was the same data that scientists such as Hueper—whom Carson cited at length—had developed decades earlier, but Carson was the first to pull it all together for a broad audience. The grassroots environmental movement ignited by Silent Spring led to the creation of the EPA in 1970 and, six years later, the passage of the Toxic Substances Control Act, which gave the agency power to regulate chemicals. Thanks to aggressive industry lobbying, the law was appallingly lax. Manufacturers weren’t required to proactively test new chemicals for safety except in rare cases, and once again, existing chemicals were grandfathered in.

By the time of the bill’s passage, DuPont and another manufacturer, the Minnesota-based 3M, had discovered that PFAS were accumulating in the blood of people around the country. Internal industry studies from this period showed that the chemicals refused to break down in the environment—meaning that every molecule the companies produced would linger on the planet for millennia. The chemicals were also found to build up rapidly in the food chain and lead to devastating health effects in lab animals. One 1978 study of PFAS in monkeys had to be aborted two months early because all of the monkeys died.

When DuPont and 3M began investigating the chemicals’ effect on workers, the results were even more troubling. A 1981 study of “pregnancy outcomes” among women in DuPont’s Teflon factory, which was later revealed through litigation, found that two of seven pregnant workers gave birth to babies with serious facial deformities, a “statistically significant excess” over the birth-defects rate in the general population. But rather than alerting employees or the public, the company simply abandoned the research.

A spokesperson for DuPont, which in 2015 spun off the division that made PFAS as part of a major restructuring, told me that he was “not in a position to speak to products that were or are a part of businesses that are owned by other independent, publicly traded companies.” A spokesperson for 3M said, “Over the decades, 3M has shared significant information about PFAS, including by publishing many of its findings regarding PFAS in publicly available journals dating back to the 1970s,” and added that 3M is on target to remove PFAS from its manufacturing globally by the end of 2025.

Limiting the use of PFAS now, however, doesn’t change how far the chemicals, and their damages, have already spread. A large body of research by independent scientists has linked forever chemicals to serious health problems, including obesity, infertility, testicular cancer, thyroid disease, neurological problems, immune suppression, and life-threatening pregnancy complications. Researchers tracking the spread of PFAS have found that they suffuse the blood of polar bears in the Arctic, eagles in the American wilderness, and fish in the depths of the ocean. They permeate snow on Mount Everest and breast milk in rural Ghana. A 2022 study of rainwater around the world found that levels of the two best-known PFAS alone were high enough to endanger the health of people and ecosystems everywhere. Less than a century after these chemicals entered the world, nowhere is pristine.

This article has been adapted from Mariah Blake’s forthcoming book, They Poisoned the World: Life and Death in the Age of Forever Chemicals.