Chapter 42: Earth's Diverse EcosystemsBizarre Facts in Biology |
Time can dramatically alter our opinion of events. This is clearly demonstrated by the two primary career accomplishments of mechanical engineer-turned-industrial chemist Thomas J. Midgley, Jr. (1889-1944): the discovery that tetraethyl lead can stop internal combustion engines from knocking; and the development of chlorofluorocarbons (CFCs) as refrigerants.
In 1921, Midgley discovered that adding a small quantity of tetraethyl lead (TEL) to gasoline prevented engine "knock." This engine-damaging malfunction is caused by premature ignition of some of the fuel in the cylinder as it is being compressed. Adding TEL to gasoline eliminated this problem, allowing manufacturers to increase the engine's compression ratio, yielding more power and greater fuel efficiency. To sell the additive to gasoline refiners, a new company called the Ethyl Corporation was formed as a joint venture of General Motors, Du Pont, and Standard Oil of New Jersey, and gasoline with the additive was called "Ethyl."
In 1928, Midgley was called on to solve another problem. The refrigerants of the day, gases that were cyclically compressed to a liquid and then allowed to vaporize, absorbing heat, were either very toxic or highly flammable, or both. And since many were also corrosive, they tended to leak, resulting in many deaths. Midgley sought a gas that avoided these problems and, reportedly in just three days, found one. It was dichlorofluoromethane, the first of the chlorofluorocarbons or "CFCs," a group later trademarked "Freons." Midgley demonstrated dichlorofluoromethane's benign properties at a meeting of the American Chemical Society in 1930 by inhaling a lung-full of the gas and gently blowing it over a lit candle, which was extinguished. Other CFCs followed quickly, and they were also used for aerosol propellants, for expanding foams, in air conditioners, etc.
For his efforts, Midgley received many honors during his lifetime, but after his death in 1944 his legacy began to unravel. Lead, whose neurotoxicity had been known since antiquity, was increasingly seen as a public health problem, causing learning disorders in children, kidney failure, hypertension and heart disease, and some cancers. In fact, within a year of the start of Ethyl production in 1923 a number of workers on the Ethyl production line went insane and died from acute lead poisoning, prompting a ban on the sale of TEL-based gasoline until an inquiry could be conducted. To alleviate fears, Midgley held a press conference during which he poured TEL over his hands and inhaled the vapor. Despite protests by many prominent scientists, the ban on sales of Ethyl was quickly lifted. Only recently has it been discovered that Midgley, suffering from severe lead poisoning, subsequently took a prolonged leave of absence in 1924 to recover. Over the next several decades nearly all the research on the effects of TEL was funded by the Ethyl Corporation. Not surprisingly, the researchers failed to find conclusive evidence that leaded gasoline posed a public health risk. The U.S. EPA began phasing out leaded gasoline use in the 1970s, a process that was completed in 1996. But this was as much because lead fouled the newly mandated catalytic converters as it was due to concerns over lead contamination of the environment. (Catalytic converters reduce emissions of nitrogen oxides, hydrocarbons, and carbon monoxide from exhaust, alleviating smog.) It has been estimated that over the 60-some years of its use, 7 million tons of lead were released into the environment from the burning of leaded gasoline in the U.S. alone. This increased our average lead exposure to 300 to 500 times that of "normal" (pre-Midgley) levels. As many as 68 million young children are believed to have received toxic levels of lead between 1927 and 1987 and as many as 5,000 deaths per year may have been caused by lead-related heart disease before TEL use was phased out. But lead burdens in humans have already declined dramatically since the phase-out.
Midgley's other major "invention," CFCs, favored just as poorly. In 1974, Mario Molina and F. Sherwood Rowland published a paper describing how stratospheric ozone gas, which absorbs harmful ultraviolet radiation from the sun, was being destroyed by chlorine released during the breakdown of CFCs. They, along with Paul Crutzen, shared the 1995 Nobel Prize in Chemistry "for their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone." While ozone levels worldwide were soon shown to be dropping fast, of particular concern was the vast reduction in ozone levels noted each year in the Southern Hemisphere around Antarctica in the so-called "ozone hole." Before long a sharp rise in skin cancer rates was noticed in the area, presumably due to elevated UV levels. It turns out that the stability of CFCs, a plus for their role as refrigerants, worked against them in the environment as it allowed many molecules to reach the stratosphere before being split by the intense ultraviolet radiation there. To make matters worse, CFCs were discovered to be greenhouse gases with Earth-warming potentials thousands of times as great as carbon dioxide. Given the serious health and climate implications, industrialized nations signed the Montreal Protocol (1987) and subsequent treaties to phase out CFC production and use.
In light of these two rather dubious (in hindsight) inventions, historian John McNeill remarked in his book on the environmental history of the twentieth century that Midgley "had more impact on the atmosphere than any other single organism in earth history." Midgley's changing legacy can be summed up by a line from a poem by James Russell Lowell; "Time makes ancient good uncouth."
References
Bryson, Bill. 2003. A Short History of Nearly Everything. New York: Broadway Books.
Kitman, J. L. 2000. The Secret History of Lead. The Nation, March 20, 2000.
McNeill, J.R. 2001. Something New Under the Sun: An Environmental History of the Twentieth-Century World. New York: Norton.