Letter | Published:

Elevated Ozone Levels in the Air of Central London


AMONG the reactions of primary pollutants with one another and with substances naturally present in air, the reactions induced by light are particularly important. The occurrence of such reactions is related to the accumulation of strongly oxidizing species, particularly ozone1, which occurs naturally in the atmosphere to the extent of 20–50 p.p.b. during daylight2,3. Ozone can be detected by smell by sensitive individuals at 100 p.p.b.4, which value is a suitable threshold for an air quality evaluation, having been proposed as an air quality standard in the USA5.

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  1. 1

    Leighton, P. A., Photochemistry of Air Pollution (Academic Press, New York, 1961).

  2. 2

    Junge, C. E., Air Chemistry and Radioactivity (Academic Press, New York, 1963).

  3. 3

    Reiter, E. R., Atmospheric Transport Processes, Part 2, Chemical Tracers (US Atomic Energy Commission, 1971).

  4. 4

    US Department of Health, Education and Welfare, Air Quality Criteria for Photochemical Oxidants (Washington: Publication No. AP-63, March 1970).

  5. 5

    US Air Resources Board, Recommended Air Quality Standards (September 1970).

  6. 6

    Daily Weather Report of the British Meteorological Office (Meteorological Office, Bracknell, Berkshire, England).

  7. 7

    Atkins, D. H. F., Cox, R. A., and Eggleton, A. E. J., Nature, 235, 372 (1972).

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