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Clair Cameron Patterson
Clair Cameron Patterson (June 2, 1922 – December 5, 1995) was a geochemist born in Mitchellville, Iowa, United States. He graduated from Grinnell College in Grinnell, Iowa.
Patterson developed the uranium-lead dating method, and using lead and uranium 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 unchanged for over 50 years.
Patterson had first encountered lead contamination in the late 1940s as a graduate student at the University of Chicago. While using a new method of lead isotope measurement to determine the age of the Earth, he found his rock samples to be contaminated. At the time, the source of the contamination was a mystery.
Estimate of the Earth's age
Harrison Brown of the University of Chicago later developed a relatively newer method for counting lead isotopes in igneous rocks, and assigned it to Patterson as a dissertation project in 1948. During this period he operated under the assumption that meteorites are left-over materials from the creation of the Solar System, and thus by measuring the age of one of these rocks the age of the Earth would be revealed. Gathering the materials required time, and in 1953, Patterson had his final specimens. He took them to the Argonne National Laboratory, where he was granted time on a late model mass spectrograph. Purportedly, he was so excited with the results that he drove home to Iowa and had his mother check him into hospital as a precaution, since he thought he was having a heart attack.
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). This number still stands.
Campaign against lead poisoning
After the completion of this work, Patterson immediately returned to the problem of his initial experiment and the contamination he had found. He determined through ice-core samples from Greenland that atmospheric lead levels had begun to increase steadily and dangerously soon after tetra-ethyl lead began to see widespread use in fuel, when it was discovered to reduce engine "knock" in internal combustion engines. Patterson subsequently identified this, along with the various other uses of lead in manufacturing, as the cause of the contamination of his samples, and 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.
Beginning in 1965, with the publication of Contaminated and Natural Lead Environments of Man, Patterson tried to draw public attention to the problem of contamination of the environment and the food chain with lead from industrial sources.
In this effort, he fought against the lobbying power of the Ethyl Corporation with all its influence (and the legacy of Thomas Midgley, which included tetra-ethyl lead and chlorofluorocarbons) and the lead additive industry as a whole, to ensure that lead was removed from gasoline (petroleum). In A Short History of Nearly Everything, author Bill Bryson notes that following his criticism of the lead industry he was refused contracts with many research organisations, including the supposedly neutral United States Public Health Service, and was excluded from a 1971 National Research Council panel on atmospheric lead contamination.
Eventually, Patterson's efforts led to the Clean Air Act of 1970, and ultimately the removal of lead from all 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.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Clair_Cameron_Patterson". A list of authors is available in Wikipedia.|