§ Mr. HinchliffeTo ask the Secretary of State for the Environment when and where World Health Organisation air quality guidelines for ozone levels have been exceeded since 1987.
§ Mr. Maclean[holding answer 10 May 1993]: There are two World Health Organisation Guidelines for the protection of human health, a one-hour guideline of 76–100ppb and an eight-hour guideline of 50ppb. There are two guidelines for the protection of plants and crops, a daily mean of 33ppb and a growing season mean of 30ppb.
Ozone monitoring has been carried out since 1987 at 16 United Kingdom sites in the Department's network. Between 1987 and 1991 the guidelines were exceeded on at least one occasion at each site. Ozone levels in the United Kingdom are, however, among the lowest in Europe.