Thomas Midgley Jr., the Most Harmful Inventor in History

Thomas Midgley Jr., born in 1889 in Dayton, Ohio, was an inventive American chemical engineer whose work profoundly shaped the 20th century, though in ways that would later prove devastating. In his early career, he tackled the problem of engine knocking, experimenting with various additives. After years of research, he developed tetraethyl lead in 1921, marketed by General Motors as “ethyl” gasoline. The additive greatly improved engine performance and was rapidly adopted worldwide, but it also released massive quantities of toxic lead into the environment. This led to widespread ecological contamination and chronic human exposure, consequences that were ignored or downplayed during Midgley’s lifetime, even as he himself suffered lead poisoning.

Seeking to move on from the controversy surrounding leaded gasoline, Midgley turned his attention to refrigeration technology, which at the time relied on hazardous substances like ammonia and sulfur dioxide. In 1928, he co-developed chlorofluorocarbons (CFCs), introducing Freon as a seemingly perfect solution: safe, stable, and non-flammable. For decades, CFCs became standard in cooling systems and aerosols.

It wasn’t until the 1970s that scientists discovered their destructive impact on the ozone layer, creating a global environmental crisis. Although CFCs were phased out under the 1987 Montreal Protocol, the atmospheric damage they caused continues to this day, cementing Midgley’s reputation as a cautionary figure in technological innovation.

Portrait of Thomas Midgley, Jr., ca. 1940s.

Midgley’s life ended with a grim irony. After contracting polio at the age of 51, he became partially paralyzed and designed an elaborate system of pulleys and ropes to help lift himself from bed. In 1944, he was accidentally strangled by this very device, dying at the age of 55.

Holding 171 patents and celebrated in his time for ingenuity, Midgley is now remembered as a man whose well-intentioned creations inadvertently caused some of the most far-reaching environmental harms in history.