TROPOSPHERIC OZONE - RESPIRATORY EFFECTS AND AUSTRALIAN AIR-QUALITY GOALS

Objective - To review the health effects of tropospheric ozone and dis cuss the implications for public health policy. Design - Literature re view and consultation with scientists in Australia and overseas. Paper s in English or with English language abstracts were identified by Med line search from the international peer reviewed published reports. Th ose from the period 1980-93 were read systematically but selected earl ier papers were also considered. Reports on ozone exposures were obtai ned from environmental agencies in the region. Results - Exposure to o zone at concentrations below the current Australian air quality goal ( 0.12 ppm averaged over one hour) may cause impaired respiratory functi on. Inflammatory changes in the small airways and respiratory symptoms result hom moderate to heavy exercise in the presence of ozone at lev els of 0.08-0.12 ppm. The changes in respiratory function due to ozone are short lived, vary with the duration of exposure, may be modified by levels of other pollutants (such as sulphur dioxide and particulate s), and differ appreciably between individuals. Bronchial lavage studi es indicate that inflammation and other pathological changes may occur in the airways before reductions in air flow are detectable, and pers ist after respiratory function has returned to normal. It is not known whether exposures to ozone at low levels (0.08-0.12 ppm) cause lastin g damage to the lung or, if such damage does occur, whether it is func tionally significant. At present, it is not possible to identify confi dently population subgroups with heightened susceptibility to ozone. P eople with asthma may be more susceptible to the effects of ozone than the general population but the evidence is not consistent. Recent rep orts suggest that ozone increases airway reactivity on subsequent chal lenge with allergens and other irritants. Animal studies are consisten t with the findings in human populations. Conclusion - A new one hour air quality ozone goal of 0.08 ppm for Australia, and the introduction of a four hour goal of 0.06 ppm are recommended on health grounds.