In December 1921, in a General Motors laboratory in Ohio, a young engineer named Thomas Midgley Jr found that adding a compound called tetraethyl lead to petrol stopped car engines from "knocking" — the destructive rattling that plagued early motors. It was a genuine technical breakthrough, and it made the modern high-powered engine possible. It also began pumping lead, a potent neurotoxin known to be poisonous since antiquity, into the air breathed by most of humanity for more than half a century. Midgley was not done. A few years later, asked to find a safer refrigerant for fridges and air conditioners, he invented chlorofluorocarbons — CFCs — the chemicals that would go on to tear a hole in the ozone layer. One historian's much-quoted verdict is that Midgley had more impact on the atmosphere than any other single organism in Earth's history.
The danger of tetraethyl lead was obvious from the start. Workers at the plants producing it began hallucinating and dying; the press dubbed one facility the "House of Butterflies", after the insects the poisoned men saw. Yet the industry insisted the additive was safe in the quantities used, and to reassure the public Midgley himself once poured the liquid over his hands and inhaled its vapour at a press conference. He was, in fact, seriously affected by lead poisoning around that time and had to take leave to recover. Leaded petrol went on to be sold worldwide, and for decades the question of whether all that airborne lead was harming the general population went largely unasked.
The man who dated the Earth
The person who forced the question was not a doctor or an activist but a geochemist with an entirely different obsession. Clair Patterson had set out, in the late 1940s and 1950s, to answer one of science's oldest questions: how old is the Earth? His method relied on measuring tiny quantities of lead isotopes, produced by the radioactive decay of uranium, in ancient meteorites — thought to be leftovers from the formation of the Solar System. In 1953 he arrived at a figure of about 4.55 billion years, a number that has stood, essentially unchanged, ever since.
But Patterson's painstaking work kept being ruined by contamination. Lead was everywhere — in his glassware, his instruments, the air of his laboratory, the very dust — swamping the minuscule natural quantities he was trying to measure. To get a clean result he had to build one of the world's first "ultra-clean" laboratories. And that experience led him to a disturbing realisation: the modern environment was saturated with lead at levels vastly higher than anything natural.
A crusade
Patterson turned detective. By comparing lead in deep ocean waters, and in layers of Arctic and Antarctic ice and ancient sediments, he showed that atmospheric lead had shot up enormously since the introduction of leaded petrol — that the contamination was recent, man-made and global. In 1965 he published a landmark paper laying out the case, and he spent much of the rest of his career campaigning against lead in fuel and food, often at real cost to himself. The lead industry fought back hard, funding rival research and pressing to keep him off government advisory panels.
He won, though slowly. From the 1970s the United States began phasing lead out of petrol, and other countries followed; measured lead levels in Americans' blood fell dramatically in step, tracking the decline in leaded fuel almost exactly. The correlation was among the most persuasive evidence that the petrol had been the culprit all along. The removal of lead from petrol is now regarded as one of the great public-health victories of the twentieth century, credited with sparing untold millions from its effects on the brain, especially in children, in whom even low doses blunt intelligence and development. Some researchers have gone so far as to link the mid-century rise and later fall in violent crime to the generation-long spike in childhood lead exposure, though that connection remains debated. Leaded petrol for ordinary cars has since been eliminated almost everywhere on Earth.
Midgley's own story ended in grim irony. Crippled by polio, he devised an elaborate system of ropes and pulleys to lift himself from bed; in 1944 he became tangled in the contraption and was strangled by it. His two great inventions long outlived him — the lead he loosed on the world, and the CFCs, which humanity would spend the end of the century frantically banning to save the ozone layer. It took another meticulous, stubborn scientist, one who only wanted to know how old the planet was, to help clean up the mess.
Quiz nuggets
- Thomas Midgley Jr discovered in 1921 that tetraethyl lead stopped engine "knock", creating leaded petrol.
- Midgley also invented CFCs, the chemicals later found to damage the ozone layer.
- Geochemist Clair Patterson dated the Earth at about 4.55 billion years in 1953, using lead isotopes in meteorites.
- Patterson's need to eliminate lead contamination from his experiments led him to expose widespread man-made lead pollution.
- Midgley died in 1944, strangled by a rope-and-pulley device he had built to lift himself from bed.