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Clair Cameron Patterson

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Clair Cameron Patterson
Clair Cameron Patterson
BornJune 2, 1922
Mitchellville, Iowa, U.S.
DiedDecember 5, 1995(1995-12-05) (aged 73)
Sea Ranch, California, U.S.
NationalityUnited States
Alma mater
Known foruranium–lead dating, age of the Earth, lead contamination
AwardsTyler Prize (1995)
V. M. Goldschmidt Award (1980)
J. Lawrence Smith Medal (1973)
Scientific career
Fieldsgeochemistry
InstitutionsCalifornia Institute of Technology
ThesisThe Isotopic Composition of Trace Quantities of Lead and Calcium (1951)
Doctoral advisorHarrison Brown

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

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

Harrison Brown of the University of Chicago developed a new method for counting lead isotopes in igneous rocks and assigned it to Patterson as a dissertation project in 1948. Patterson operated under the assumption that meteorites are left-over materials from the formation of the solar system, and thus measuring the age of one of these rocks would reveal the age of the Earth. Gathering the materials required time, and in 1953, Patterson had his final specimens from the Canyon Diablo meteorite. He took them to the Argonne National Laboratory, where he was granted time on a late-model mass spectrometer.

In a meeting in Wisconsin soon afterward, Patterson revealed the results of his study. The definitive age of the Earth is 4.550 billion years (give or take 70 million years). The current estimate for the age of the earth is 4.54 ± 0.05 billion years (4.54 × 109 years ± 1%).[4][5][6]

Tracing geochemical evolution of Earth

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

Further information: 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.[7]

The United States mandated the use of unleaded gasoline to protect catalytic converters in all new cars starting with the 1975 model year,[8] 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.[9]

He then turned 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.[10]

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.[11]

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.[12] 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.

Death

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.[13]

Awards and honors

Memorials

References

  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. ^ "Age of the Earth". U.S. Geological Survey. 1997. Archived from the original on 23 December 2005. Retrieved 2006-01-10. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  5. ^ Dalrymple, G. Brent (2001). "The age of the Earth in the twentieth century: a problem (mostly) solved". Special Publications, Geological Society of London. 190 (1): 205–221. Bibcode:2001GSLSP.190..205D. doi:10.1144/GSL.SP.2001.190.01.14.
  6. ^ Manhesa, Gérard; Allègre, Claude J.; Dupréa, Bernard; Hamelin, Bruno (1980). "Lead isotope study of basic-ultrabasic layered complexes: Speculations about the age of the earth and primitive mantle characteristics". Earth and Planetary Science Letters. 47 (3): 370–382. Bibcode:1980E&PSL..47..370M. doi:10.1016/0012-821X(80)90024-2.
  7. ^ Same (NAS) source as above See p. 14.
  8. ^ The U.S. Experience with the Phasedown of Lead in Gasoline (PDF), 2003-06-15, retrieved 2014-12-12
  9. ^ Blood Lead Levels Keep Dropping; New Guidelines Proposed for Those Most Vulnerable, 1997-02-20, retrieved 2016-01-13
  10. ^ 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
  11. ^ 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
  12. ^ Lead in the Human Environment, Washington, D.C.: National Academy of Sciences, 1980
  13. ^ Dicke, William "Clair C. Patterson, Who Established Earth's Age, Is Dead at 73"

Further reading

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