May 18, 1889 - November 2, 1944: Age 55
Thomas Midgley had more impact on the ozone layer than any other single organism on the planet. That's because, as a scientist in the 1930s, he discovered dichlorodifluoromethane, a chlorinated fluorocarbon (CFC) which he named Freon. This substance was to become widely used in heat pumps, refrigerators, and aerosol sprays, and to set up a cycle of ozone depletion. Ozone is a molecule consisting of three oxygen atoms. Its presence in the upper atmosphere filters harmful ultraviolet rays from the sun. Since 1980 the ozone in the upper atmosphere has depeleted, resulting in overall thinning of the ozone layer year-round, as well as drastic thinning of the ozone layer over the polar regions during the spring (called the "ozone hole"). The depletion is caused by CFCs that have been steadily pouring into to atmosphere since the 1930s. CFCs are not banned in many countries, and plans are to ban them worldwide by 2010.
That wasn't Midgley's only contribution to the atmosphere: he also discovered that adding ethyl (tetra-ethyl lead) to gasoline made engines run more efficiently. This discovery resulted in the rapid development of better engines which, among other things, gave the US a decisive advantage in air combat during WWII. Workers who had extensive contact with the compounds often suffered from health effects: even Midgley himself had to take a leave of absence when his lungs became affected by working with lead. However it wasn't until the 1970s, many years after his death, that wider public concerns about air pollution surfaced, and in the 1990s leaded gasoline was banned in America for many (but not all) uses. Plans are to ban it completely by 2008, however it is still widely sold and used in the Third World.
Midgley contracted polio when he was 51, resulting in severe disability. Ever the scientist, he developed a system of ropes and pulleys to lift himself out of bed. On November 2, 1944 he became entangled in the ropes and died of suffocation.
Sources: Wikipedia, Invent Now Hall of Fame