report no. 3/14

31 Jan 2014

This report summarises the assessment of the policy relevant long-term healthstudies published since the last update of the ozone Air Quality Limit Value (AQLV).This project was undertaken in preparation for the European Union 2013 Year of Airdiscussions on the Air Quality Directives, and the impact of new health science onthe AQLV for key pollutants, including ozone. The types of studies reviewed in thisassessment included chronic mortality and morbidity air pollution epidemiologystudies and repeat-dose toxicology and mechanistic studies. For each study, a summary of the findings as reported was prepared along with acritical review identifying the strengths and weaknesses of the study, In totalthirteen chronic mortality studies, nine respiratory morbidity studies, nineepidemiology studies evaluating long-term exposure to zone and pulmonary functionand nine repeat dose animal inhalation studies were reviewed. Reliability scoreswere provided for both the epidemiology and toxicology studies, and a weight-ofevidence approach was implemented to determine causality. In summary, for chronic mortality, the data were considered not sufficient to draw acausal conclusion between long-term exposure to zone and mortality. The availabletoxicology and mechanistic data did not support the mortality hypothesis at currentambient ozone levels since much higher levels (500 ppb) were required to produceserious effects. For chronic morbidity, the data were considered insufficient toestablish a causal relationship between long-term exposure to ozone and new onsetasthma. In addition, the data do not indicate that long-term exposure to ozone atcurrent ambient levels causes reductions in lung function development. Short-termexposure to higher levels of ozone can cause transient change in lung functionwhich, if accompanied with symptoms, could be considered as adverse. Theserious effects in animals as a result of repeated high level (500 ppb) exposure arenot expected to occur in humans exposed to ambient levels. In summary, the quality of the evidence to evaluate the association between chronicexposure to ozone and mortality is highly unreliable, and information to support anobjectively-based Air Quality Target Values (AQTV) is lacking.