Inventions through history have often made everyday tasks easier and some, like trains, the cotton gin, printing press, and computers, have been revolutionary. But other inventions have backfired and proven to be detrimental in the long run. Among those who contributed some of history’s most dangerous innovations was a bespectacled chemist from Beaver Falls, Pennsylvania.

Thomas Midgley, Jr. introduced the world to both leaded gasoline and chlorofluorocarbons (CFCs), now considered two of the world’s most harmful chemical compounds. While Midgley won multiple prestigious awards during his lifetime, research in recent decades has shown how the compounds he developed for use in cars and refrigerators ended up ravaging the environment and poisoning people.

Midgley, born on May 18, 1889, graduated with a degree in mechanical engineering from Cornell University in 1911. In 1916, he joined General Motor’s Delco research laboratory under Charles Kettering to work on improvements to automobiles. His focus was tackling the problem of engine knock.

Knock was a common problem in early 20 century engines. When an engine neared its maximum load, it made pinging noises that could destroy it. After a lengthy study, Midgley discovered that tetraethyl lead (TEL) as a fuel additive virtually eliminated knock. Even better, he found that TEL increased engine performance and speed. With the support of GM, oil companies, and car manufacturers, TEL went on the market on February 1, 1923 under the brand name Ethyl. GM and Standard Oil formed the Ethyl Corporation to handle manufacturing and sales. Midgley became a vice president and served on the board of directors.

The Ethyl Corporation never mentioned “lead” when marketing TEL since the dangers of lead poisoning were well known. The corporation insisted that TEL was safe, but, at the same time, encountered their own dangerous episodes with the chemical. In October 1924, at an experimental plant in New Jersey, five workers died and 35 others experienced tremors, hallucinations, and other symptoms of lead poisoning. Midgely, himself, had been poisoned by inhaling fumes of TEL and washing his hands in the stuff to demonstrate its safety. He was forced to take a vacation to cure himself—but the incident did not prevent him from advocating for Ethyl. Instead, he took the corporate position that workers didn’t take proper precautions.

David Rosner, a historian at Columbia University and co-author of Lead Wars and Deceit and Denial says, “Midgley had an enormous interest in self-delusion when it came to a product that he was so connected to. Of course, he had an ethical dilemma. Whether he fooled himself, lied, or was just oblivious to what future generations would have to deal with is beyond me.”

The scandal at the research plant prompted several states to ban TEL. But then the tide turned. The federal Bureau of Mines released a study, heavily influenced by corporate pressure, which asserted that TEL was safe. This and an aggressive marketing campaign established gasoline-infused with TEL (leaded gasoline) as the fuel of choice. In the ensuing decades, lead exposure resulted in a string of health maladies, particularly among children. One recent study hypothesized that increased lead exposure may have contributed to the mid-20 century rise in crime.

Starting in the 1970s TEL was phased out and as of 2017 only produced in a few places in the world. But lead contamination remains in areas where TEL-fueled vehicles were common.

Midgley’s next problematic innovation was chlorofluorocarbons (CFCs). CFCs were developed to solve a long-standing problem with early refrigerators: they were extremely unsafe.

“The best early refrigerants were ether and ammonia, both flammable,” explains Tom Jackson, author of Chilled: How Refrigeration Changed the World and Might Do So Again. Jackson describes how an industrial-scale refrigerator on display at the 1893 Chicago World’s Fair caught fire and eventually exploded, killing 17 firefighters. _“_The domestic refrigerators that followed around 30 years later used sulfur dioxide, which although not flammable was highly toxic. Leaks of this gas killed families in their sleep.”

GM’s refrigerator division, Frigidaire, had been showing losses for years. Midgley with a team of scientists undertook a search for a non-toxic, non-flammable refrigerant. In 1930, they found a solution in dichlorodifluoromethane, which they sold under the brand name freon-12. This was the world’s first CFC. To demonstrate its safety, Midgley inhaled the stuff and blew out a candle.

Freon caught on and became ubiquitous in refrigerators, cooling units and aerosol spray cans as propellants. What Midgely did not know is that CFCs deplete the Earth’s ozone layer which protects life from ultra violet and other forms of radiation. Even worse, CFC’s are super greenhouse gases which contributes to global warming and climate change at a much greater rate than even carbon dioxide.

Even though CFC’s like freon-12 were banned or severely restricted starting with the Montreal Protocol in 1987, they linger in the atmosphere. According to National Oceanic and Atmospheric Administration, CFCs have an atmospheric lifespan of up to 140 years.

Lauded, Midgley won almost every prestigious award in his profession. He was given the Willard Gibbs Medal, the Nichols Medal, the Priestly Medal, and the Perkin Medal. Aside from TEL and freon, Midgley also held about 170 other patents. It is only in recent decades that the damaging consequences of his inventions became known.

Midgley is not solely responsible for all the environmental ills generated by TEL and CFCs. Businesses of the day often disregarded the potential impact of pollutants in the environment either by underestimating the impact of those pollutants or thinking that it was a negligible problem. Neither was there any appreciable regulation of potential pollutants.

In the case of CFCs, he believed them to be less harmful than exploding refrigerators. “I think it would be unfair to criticize Midgley for his work on CFCs,” says Jackson. “They were an inelegant solution to a commercial problem, but one that Midgley and others thought was safe.”

On the other hand, Jackson says that since the toxic effects of lead were already known in the 1920s when he developed leaded fuel, “he must have been aware of possible health damage…but went ahead anyway.”

In 1940, Midgley contracted polio and was paralyzed. Ever the inventor, he developed a harness system of ropes and pulleys to help him maneuver and get out of bed. In an ironic twist, his invention strangled him to death on November 2, 1944.