Clair Patterson

Clair Cameron Patterson (June 2, 1922 – December 5, 1995) From a young age he developed an intellectual curiosity Both students attended graduate school at the University of Iowa, where he completed an M.A. in molecular spectroscopy and they married in 1944.

After World War II, the Pattersons returned to Chicago, where Laurie worked as an infrared spectroscopist and supported Patterson while he studied for his Ph.D. at the University of Chicago under Harrison Brown. While conducting experiments in an old laboratory, Patterson uncovered "the widespread presence of lead as a contaminant throughout the laboratory, including in his own hair." (This subject—the occurrence of lead broadly in the atmosphere and the environment—came to be a focus of study later in his career. His later work produced shocking results showing the ubiquitous presence of toxic lead in the broad environment.) After a postdoctoral year at Chicago, in 1952 Patterson moved with Brown to the California Institute of Technology (Caltech) in Pasadena, California, specifically to the (now) Division of Geological and Planetary Sciences, where they served as founding members of Caltech's new geochemistry program. He remained at Caltech for the rest of his life. He and Laurie had four children.

Measurement of the Earth's age

Patterson's postdoc work at the University of Chicago was under Harrison Brown, who teamed him with George Tilton to study geological aging of zircon crystals. Zircon is extremely useful for geological dating: when forming, it collects tiny imperfections of uranium, but never lead. It follows that if lead is present in zircon, it must have come from decay of the uranium present. (The process is known as U-Pb dating.) The team measured the concentrations and isotopic compositions of foreign elements inside the zircon. Tilton measured the uranium and Patterson the types and amounts of lead. Patterson's goal was to calculate the composition of primordial lead in the Earth. Then it would be possible to calculate the age of the Earth—and, in turn, of the Solar System by using the same techniques on meteorites.

After beginning their work in 1948, Patterson soon noted that his lead samples were being contaminated. The age of the igneous rock from which the zircon came was known, and Tilton's uranium measurements aligned with what was expected in the zircon at that particular age; but Patterson's data typically was skewed with "too much" lead. a figure that has remained largely unchallenged since.

Tracing geochemical evolution of Earth

Patterson's ability to isolate quantities of lead at microgram levels from ordinary rocks and to determine their isotopic compositions enabled him to analyse for lead in sediment samples of the Atlantic and Pacific oceans. Deriving comparative bases from the different ages during which landmasses had drained into the oceans, he showed that the impact of anthropogenic lead being dispersed into the environment was more than 100 times the amount of lead leached naturally into the ocean by surface streams. To Patterson, the Earth's geochemical cycle for lead appeared to be badly out of balance.

To work around the limitations of then-available analytic procedures, Patterson developed new approaches. He found that in comparing similar metals, such as barium, ocean waters contained up to 20 times more lead than ocean waters.

Following Kehoe's arguments, observed levels of lead in blood, soil, or air were broadly referred to as "normal", meaning values near the average; it was assumed that because these levels were common, they were harmless. "Normal" also carries some of the meaning "natural". Patterson argued that the word "normal" should be replaced with "typical", and that just because a certain level of lead was commonplace, it did not mean it was harmless. "Natural", he insisted, was limited to concentrations of lead that existed before human activity produced significant lead contamination, which of late had occurred broadly—especially after the beginning of the industrial revolution.

Patterson focused his attention and his advanced laboratory techniques on lead contamination in food, for which official testing data also reported marked increases. In one study, he showed an increase in lead levels from 0.3 ng/g to 1400 ng/g—in certain canned fish compared with fresh fish—where the official laboratory had reported an increase from 400 ng/g to 700 ng/g. He compared levels of lead, barium, and calcium in 1600-year-old Peruvian skeletons and showed a 700- to 1200-fold increase in lead levels of modern human bones, with no comparable changes in the barium and calcium levels.

Starting with the 1975 model year, the United States mandated the use of leaded gasoline to protect catalytic converters in all new cars. However, Patterson's efforts achieved an accelerated phaseout of lead from standard automotive gasoline—but not all leaded fuels—in the United States by 1986. Leaded automotive gasoline was finally completely banned in the USA on January 1, 1996, although it is still used for aviation, which is currently the largest contributor to human lead exposure. By the late 1990s, lead levels in the blood of Americans were reported to have dropped by up to 80%.

In 1978, Patterson was appointed to a National Research Council panel that acknowledged many of the increases of lead contamination and the need for reductions, but some members argued for more research before recommending action. Patterson expressed his opinions in a 78-page minority report, which argued that control measures in certain sensitive sectors—including all leaded fuels, public water distribution systems, food containers, paints and glazes—should start immediately.

Death

Patterson died in his home in Sea Ranch, California, at the age of 73 on December 5, 1995.

V. M. Goldschmidt Award, 1980 (Geochemical Society)
Tyler Prize for Environmental Achievement, 1995 (University of Southern California)
Minor planet 2511 Patterson is named in his honor.

Memorials

Clair C. Patterson Award, awarded annually since 1998 by the Geochemical Society

Legacy

Patterson was referenced in a 2022 documentary by Derek Muller, The Man Who Accidentally Killed The Most People In History. Patterson was also featured in "The Clean Room," the seventh episode of the American documentary television series Cosmos: A Spacetime Odyssey.

References

External links

Clair Cameron Patterson (Geochemist) at The Caltech Archives