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Clair Patterson helped us breathe freely

Clair Cameron Patterson didn’t have far to travel when he returned to civilian life at the end of World War II.

The young geochemical researcher was one of the scientists assembled at the University of Chicago, and later Oak Ridge, Tennessee, to work on the Manhattan Project, and after the war he returned to the University of Chicago to earn a PhD.

Clair Patterson redistilling a reagent in his laboratory in 1957. Credit: Caltech E&S Magazine

Born in rural Iowa on 2 June 1922, he had completed a Masters degree in molecular spectroscopy at the University of Iowa before his studies took an enforced break.

His PhD supervisor was Harrison Brown, who also had been involved in the project to build an atomic bomb, and knowing of Patterson’s experience working with a mass spectrometer and uranium he encouraged him to isolate lead from an iron meteorite and determine its isotopic composition.

Brown had determined the age of the Earth by measuring the isotopic composition of lead in iron meteorites, Roger Revelle says in Biographical Memoirs volume 65, published by the US National Academy of Sciences.

His theory was that the age of the Earth could “be obtained from mathematical combinations of decay parameters and isotopic composition of uranium today with isotopic compositions of the Earth’s lead, today and at the time it was formed”.

“All of these had been measured and were reasonably well known except the last item, the isotopic composition of primordial lead.”

In volume 74 of Biographical Memoirs, Patterson’s colleague George Tilton writes that Patterson “spent some five years establishing methods for the separation and isotopic analysis of lead at microgram and sub-microgram levels. His techniques opened a new field in lead isotope geochemistry for terrestrial as well as for planetary studies”.

Brown moved to the California Institute of Technology (CalTech) in 1952, and Patterson joined him the following year.

Another year later, Tilton says, Patterson had carried out “the definitive study, using the troilite (sulfide) phase of the Canyon Diablo iron meteorite to measure the isotopic composition of primordial lead, from which he determined an age for the Earth”.

“Harrison Brown’s suspicion was finally confirmed!” Tilton says. “The answer turned out to be 4.5 billion years, later refined to 4.55 billion years.”

At the start of this research, Patterson had come across an unexpected problem.

As a 2015 article titled “Getting the Lead Out”, published by CalTech Media Relations, explains, Patterson had announced his findings at a conference in 1955, and had continued to refine his results as the paper worked its way through the review process.

“But there he hit a snag – his analytical skills had become so finely honed that he was finding lead everywhere. He needed to know the source of this contamination in order to eliminate it, and he took it on himself to find out.”

Since the 1920s petroleum companies had been adding tetraethyl lead to their petrol to improve performance in internal combustion motors. There was also lead in paint, in plumbing, in food containers, even in children’s toys.

Now, little more than 30 years later, Patterson found build-ups of lead in the environment that were shocking. But when he began presenting his findings, he found himself pitted against the special interest might of pretty much the industrialised world, plus governments, and even some scientists.

In 1965 he published a paper titled “Contaminated and Natural Lead Environments of Man”, in the journal Archives of Environmental & Occupational Health, and despite receiving widespread criticism and even derision, he continued his research into lead pollution.

He found evidence that “the atmosphere of the northern hemisphere contains about 1000 times more than natural amounts of lead” and, CalTech says, “he called for the ‘elimination of some of the most serious sources of lead pollution such as lead alkyls [tetraethyl lead], insecticides, food can solder, water service pipes, kitchenware glazes, and paints; and a reevaluation by persons in positions of responsibility in the field of public health of their role in the matter’.”

It says Patterson’s paper was “his first shot in the war against lead pollution, bureaucratic inertia, and big business that he would wage for the rest of his life”.

He won. In 1970 the US passed the Clean Air Act, which began the development of national air-quality standards, including emission controls on cars. The Consumer Product Safety Commission would ban lead-based indoor house paints in 1977, and in 1986 the Environmental Protection Agency prohibited tetraethyl lead in gasoline.

Patterson died in his home in Sea Ranch, California, on 5 December 1995.

The Clair C Patterson Award is now presented annually by the Geochemical Society to recognise an innovative breakthrough of fundamental significance in environmental geochemistry, particularly in service of society.

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