Recommendation for an Air Quality Standard for Ozone

24. The Panel recommend an Air Quality Standard for ozone in the United Kingdom of 50 ppb as a running 8-hour average.
25. This recommendation is intended to reduce the exposure of the population, including individuals who may be particularly sensitive, to levels at which harmful effects are unlikely to occur. We recommend that techniques for monitoring the Standard are consistent with those of the Department of the Environment's national ozone monitoring networks.
26. We recognise that this is an ambitious Standard which will need international action to be achieved. In order to monitor progress we recommend that ozone monitoring data in the United Kingdom are reported in terms of the number of days in which the Standard is exceeded at any one site per year. We note from past evidence that if the 50 ppb 8-hour running average is exceeded on less than 10 days per year, at any one site, then the maximum 8-hour concentration at that site is unlikely to exceed 100 ppb, a concentration at which effects in healthy individuals have been clearly demonstrated.