Clair Cameron Patterson

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Clair Cameron Patterson
Portrait of Clair Cameron Patterson.jpg
Clair Cameron Patterson
Born June 2, 1922
Mitchellville, Iowa, U.S.
Died December 5, 1995(1995-12-05) (aged 73)
Sea Ranch, California, U.S.
Nationality United States
Fields geochemistry
Institutions California Institute of Technology
Alma mater
Thesis The Isotopic Composition of Trace Quantities of Lead and Calcium (1951)
Doctoral advisor Harrison Brown
Known for uranium–lead dating, age of the Earth, lead contamination
Notable awards Tyler Prize (1995)
V. M. Goldschmidt Award (1980)
J. Lawrence Smith Medal (1973)

Clair Cameron Patterson (June 2, 1922 – December 5, 1995) was an American geochemist. Born in Mitchellville, Iowa, United States he graduated from Grinnell College. He later received his Ph.D. from the University of Chicago, and spent his entire professional career at the California Institute of Technology.

In collaboration with George Tilton, Patterson developed the uranium–lead dating method into lead–lead dating and, by using lead isotopic data from the Canyon Diablo meteorite, he calculated an age for the Earth of 4.55 billion years; a figure far more accurate than those that existed at the time and one that has remained largely unchanged since 1956.

Patterson had first encountered lead contamination in the late 1940s as a graduate student at the University of Chicago. His work on this led to a total re-evaluation of the growth in industrial lead concentrations in the atmosphere and the human body, and his subsequent campaigning was seminal in the banning of tetraethyllead in gasoline and lead solder in food cans.

Early life[edit]

Clair (Pat) Patterson was born in Mitchellville, Iowa, and graduated from Grinnell College in chemistry where he met his future wife, Lorna (Laurie) McCleary. They both moved to the University of Iowa, for graduate work, where he got an M.A. in molecular spectroscopy. Both were then sent to work on the Manhattan Project, first at the University of Chicago and then at Oak Ridge, Tennessee, where he encountered mass spectrometry.[1]

After the war, they returned to Chicago, where Laurie took a research job as an infrared spectroscopist to support Pat while he got a Ph.D. at the University of Chicago under Harrison Brown. After a postdoctoral year at Chicago, Patterson moved with Brown to the Division of Geology (later the Division of Geological and Planetary Sciences) at the California Institute of Technology in 1952, as founding members of its geochemistry program.[2] Pat remained at Caltech for the rest of his life. He and Laurie had four children.[3]

Estimate of Earth's age[edit]

After World War II, Pat returned to the University of Chicago where he worked under his research adviser, Harrison Brown. Brown, knowing about Patterson experience with mass spec, teamed him up with George Tilton to do geological aging on zircons. Zircons are extremely useful for dating since when they are formed they possess tiny imperfections of uranium inside them but no lead. Therefore, if any lead is present in the zircon it must come from the decay of uranium. This process is known as U-Pb dating. The duo’s job was to measure the concentration and isotopic compositions of the elements inside the zircon. Tilton was to measure the uranium and Pat, the amount and type of lead. The goal for Patterson was to figure out the composition of the primordial lead in the Earth. In doing so, it would be possible to figure out the age of the solar system, and in turn the Earth, from using the same techniques on meteorites.

As Patterson and Tilton began their work in 1948, Patterson quickly became aware that his lead samples were being contaminated. They knew the age of the igneous rock in which the zircon came from and Tilton’s uranium measurements aligned with what should be in a zircon at that particular age, but Pat’s data was always skewed with too much lead. After six years the team did publish a paper on methods of determining the ages of zircon crystals and Patterson’s did achieve his PhD, but they were no closer in determining the age of the Earth.

Harrison was able to receive a grant from the Atomic Energy Commission to continue work on dating the Earth but more importantly to commission a new mass spectrometer in Pasadena, Ca at Caltech. In 1953, Harrison brought Patterson along with him and at Caltech Pat was able to build his own lab from scratch. In it he secured all points of entry for air and other containments. Patterson also acid cleaned all apparatuses and even distilled all of his chemicals shipped to him. He in essence created one of the first clean rooms ever in order to prevent lead contamination of his data. He was then able to finish his work with the Canyon Diablo meteorite. He used the mass spectrometer at the Argonne National Laboratory on isolated iron-meteorite lead to collect data on the abundance of lead isotopes. With the new data, in 1956 he published “Age of Meteorites and the Earth,” the first paper containing the true age of the solar system’s accretion which was 4.550Gy ± 70My.[4][5][6][7]

Tracing geochemical evolution of Earth[edit]

His ability to isolate microgram quantities of lead from ordinary rocks and determine their isotope composition led him to examining the lead in ocean sediment samples from the Atlantic and the Pacific. Deriving from the different ages at which the landmasses had drained into the ocean, he was able to show that the amount of anthropogenic lead presently dispersed into the environment was about 80 times the amount being deposited in the ocean sediments: the geochemical cycle for lead appeared to be badly out of balance.

The limitations of the analytic procedures led to him using other approaches. He found that deep ocean water contained 3 to 10 times less lead than surface water, in contrast to similar metals like barium. That led him to doubt the commonly held view that lead concentrations had grown by only a factor of two over naturally occurring levels.

Patterson returned to the problem of his initial experiment and the contamination he had found in the blanks used for sampling. He determined, through ice-core samples from Greenland, that atmospheric lead levels had begun to increase steadily and dangerously soon after tetraethyl lead began to see widespread use in fuel, when it was discovered to reduce engine knock in internal combustion engines. Patterson subsequently identified that, along with the various other uses of lead in manufacturing, as the cause of the contamination of his samples. Because of the significant public-health implications of his findings, he devoted the rest of his life to removing as much introduced lead from the environment as possible.

Campaign against lead poisoning[edit]

For more details on this topic, see Lead poisoning.

Beginning in 1965, with the publication of Contaminated and Natural Lead Environments of Man, Patterson tried to draw public attention to the problem of increased lead levels in the environment and the food chain from lead from industrial sources. Perhaps partly because he was criticizing the experimental methods of other scientists, he encountered strong opposition from recognized experts, such as Robert A. Kehoe.

In his effort to ensure that lead was removed from gasoline (petrol), Patterson fought against the lobbying power of the Ethyl Corporation (which employed Kehoe), against the legacy of Thomas Midgley, Jr. (which included tetraethyllead and chlorofluorocarbons), and against the lead additive industry as a whole. Following Patterson's criticism of the lead industry, he was refused contracts with many research organizations, including the supposedly neutral United States Public Health Service.

In 1971, he was excluded from a National Research Council (NRC) panel on atmospheric lead contamination even though he was then the foremost expert on the subject.[8]

The United States mandated the use of unleaded gasoline to protect catalytic converters in all new cars starting with the 1975 model year,[9] but Patterson's efforts accelerated the phaseout of lead from all standard, consumer, automotive gasoline in the United States by 1986. Lead levels within the blood of Americans are reported to have dropped by up to 80% by the late 1990s.[10]

Most people, following Kehoe’s arguments, referred to ‘‘normal levels’’ of lead in blood, soil, and air, meaning values near the average. They assumed that because these levels were common, they were harmless. ‘‘Normal’’ also carries some of the meaning ‘‘natural.’’ Patterson argued that ‘‘normal’’ should be replaced by ‘‘typical.’’ Simply because a certain level of lead was commonplace did not mean it was without harm. ‘‘Natural,’’ he insisted, was limited to concentrations of lead that existed in the body or environment before contamination by man.

Due to his ultraclean chamber, considered one of the first clean rooms, his measurements of isotopic ratios were free of the contamination that confounded the findings of Kehoe and others. Where Kehoe measured lead in ‘‘unexposed’’ workers in a TEL plant and Mexican farmers, Patterson studied pre-iron age mummies and tuna raised from pelagic waters.

Kehoe claimed that mankind has adapted to environmental lead. Patterson’s precise point was that man had recently increased the concentration of lead and that the short span of exposure, a few thousand years, was an instant in the Darwinian time scale, nowhere near the time needed to develop adaptive responses.[11]

Patterson focused his attention to lead in food, for which similar experimental deficiencies had also masked increases. In one study, he showed an increase in lead levels from 0.3 to 1400 ng/g in certain canned fish compared with fresh, whilst the official laboratory had reported an increase of 400 ng/g to 700 ng/g.[12]

He compared the lead, barium, and calcium levels in 1600-year-old Peruvian skeletons and showed a 700- to 1200-fold increase in lead levels in modern human bones, with no comparable changes in the barium and calcium levels.[13]

In 1978, he was appointed to a NRC panel that acknowledged many of the increases and the need for reductions but argued the need for more research.[14] His opinions were expressed in a 78-page minority report, which argued that control measures should start immediately, including gasoline, food containers, paint, glazes, and water distribution systems.


Patterson died in his home in Sea Ranch, California at the age of 73 on December 5, 1995. The reported cause of his death was a severe asthma attack..[6]

Awards and honors[edit]



  1. ^ Biographical memoir by George R. Tilton
  2. ^ Interview with Shirley Cohen from the Caltech Oral History archives
  3. ^ Biographical Memoirs of the National Academy of Sciences (NAS) for Clair C. Patterson See p. 17.
  4. ^ Cohen, Shirley "Duck Soup and Lead"
  5. ^ Degrasse-Tyson, Neil (20 April 2014). "The Clean Room". Cosmos: A Spacetime Odyssey. Fox. 
  6. ^ a b Dicke, William "Clair C. Patterson, Who Established Earth's Age, Is Dead at 73"
  7. ^ Patterson, C. (1956), "Age of meteorites and the Earth", Geochimica et Cosmochimica Acta, 10 (4): 230–237, Bibcode:1956GeCoA..10..230P, doi:10.1016/0016-7037(56)90036-9 
  8. ^ Same (NAS) source as above See p. 14.
  9. ^ The U.S. Experience with the Phasedown of Lead in Gasoline (PDF), 2003-06-15, retrieved 2014-12-12 
  10. ^ Blood Lead Levels Keep Dropping; New Guidelines Proposed for Those Most Vulnerable, 1997-02-20, retrieved 2016-01-13 
  11. ^ Needleman, H.L. (1998), "Clair Patterson and Robert Kehoe: Two Views of Lead Toxicity", Environmental Research, 78.2: 79–85 
  12. ^ Settle, D. M.; Patterson, C. C. (1980), "Lead in albacore: guide to lead pollution in Americans", Science, 207 (4436): 1167–76, Bibcode:1980Sci...207.1167S, doi:10.1126/science.6986654, PMID 6986654 
  13. ^ Ericson, J.E.; Shirahata, H.; Patterson, C.C. (1975), "Skeletal concentrations of lead in ancient Peruvians", N. Engl. J. Med., 300: 946–51, doi:10.1056/nejm197904263001703 
  14. ^ Lead in the Human Environment, Washington, D.C.: National Academy of Sciences, 1980 

Further reading[edit]

  • Patterson, C.; Chow, T. J. (1962), "The occurrence and significance of lead isotopes in pelagic sediments", Geochimica et Cosmochimica Acta, 26 (2): 263–308, Bibcode:1962GeCoA..26..263C, doi:10.1016/0016-7037(62)90016-9 
  • Patterson, C. (1965), "Contaminated and natural lead environments of man", Arch. Environ. Health, 11: 344–360, doi:10.1080/00039896.1965.10664229, PMID 14334042 
  • Bryson, Bill (2004), A Short History of Nearly Everything, Broadway, pp. 149, 156–160, ISBN 978-0-7679-0818-4 
  • Casanova, I (1998), "Clair C. Patterson (1922-1995), discoverer of the age of the Earth", Int. Microbiol. (published Sep 1998), 1 (3), pp. 231–2, PMID 10943366 
  • Davidson, Cliff I., ed. (1998), Clean Hands: Clair Patterson's Crusade against Environmental Lead Contamination, New York: Nova Science Publishers, pp. xxxiv+162, ISBN 1-56072-568-0 
  • Denworth, L. Toxic Truth: A Scientist, A Doctor, and the Battle over Lead, Beacon Press, 2009.
  • Flegal, A (1998), "Clair Patterson's Influence on Environmental Research", Environ. Res. (published Aug 1998), 78 (2), pp. 65–185, PMID 9719609 
  • Flegal, A R (1998), "Clair Patterson's influence on environmental research", Environ. Res. (published Aug 1998), 78 (2), pp. 64–70, Bibcode:1998ER.....78...65F, doi:10.1006/enrs.1998.3861, PMID 9725987 
  • McGrayne, S. Bertsch (2002), "Ch. 9: Lead-Free Gasoline and Clair C. Patterson", Prometheans in the Lab, New York: McGraw-Hill, ISBN 0-07-140795-2 
  • Needleman, H L (1998), "Clair Patterson and Robert Kehoe: two views of lead toxicity", Environ. Res. (published Aug 1998), 78 (2), pp. 79–85, Bibcode:1998ER.....78...79N, doi:10.1006/enrs.1997.3807, PMID 9719611 
  • Nriagu, J O (1998), "Clair Patterson and Robert Kehoe's paradigm of "show me the data" on environmental lead poisoning", Environ. Res. (published Aug 1998), 78 (2), pp. 71–8, Bibcode:1998ER.....78...71N, doi:10.1006/enrs.1997.3808, PMID 9719610 
  • Tilton, George R., Clair Cameron Patterson, retrieved 2009-03-10 

External links[edit]