The first big problem Midgley turned his attention to was that of ‘knock’ in early petrol engines, which meant they had to be designed with low efficiency and performance. After six years experimentation Midgley found what seemed to be the perfect solution: simply add a small quantity of tetraethyl lead to petrol. Unfortunately no one realised the eventual result would be millions of tons of toxic lead dust entering the atmosphere and contaminating the bodies and brains of, in particular, young children. It was 50 years before lead began to be phased out of petrol.

Long before that though -- in the 1930s -- Midgley had another great idea. Early refrigerators used highly toxic chemicals such as sulphur dioxide and ammonia, which worked but killed people when they leaked. Midgley took only three days to come up with a concoction of halogen gases that was almost inert, certainly non-toxic, and became known to the world as CFCs. It was a brilliant piece of science, but what he had failed to foresee was that CFC's would get into the atmosphere, both from leaking or scrapped refrigeration plants and later from the domestic aerosol. There they would combine with ozone in the upper atmosphere, breaking it down and thinning the crucially important ozone layer that protects human and most other life on earth from excessive ultraviolet solar radiation.

At the age of 51 Midgley developed polio and was severely disabled. Characteristically he turned his inventive mind to making complex hoists and other devices to help him cope around the house. One day he became entrapped in this device and was strangled. He died in 1944, aged 55, garlanded with awards and recognised then as one of America’s greatest chemists.