Copyright ©ERS Journals Ltd 1998 European Respiratory Journal

Asthmatics have been shown to be greatly affected by environmental exposure. Both experimental [1] and epide-miological studies [2] have shown air pollution to aggra-vate asthma problems. Concern about the possible adverse respiratory effects of major ambient air pollutants has stim-ulated investigators to attempt to relate effects to lower and lower concentrations in the search for minimum con-centrations at which adverse effects on health are detecta-ble. As a result of such studies, even in relatively weakly polluted areas, the guidelines and limits for several pollut-ants are now under revision and acceptable limits from a health point of view are expected to be set at increasingly lower levels. Daily diaries of respiratory health are very useful in studies of the effects of air pollution on susceptible per