Long-term exposure to ambient ozone and mortality: a quantitative systematic review and meta-analysis of evidence from cohort studies.

OBJECTIVES: While there is good evidence for associations between short-term exposure to ozone and a range of adverse health outcomes, the evidence from narrative reviews for long-term exposure is suggestive of associations with respiratory mortality only. We conducted a systematic, quantitative evaluation of the evidence from cohort studies, reporting associations between long-term exposure to ozone and mortality. METHODS: Cohort studies published in peer-reviewed journals indexed in EMBASE and MEDLINE to September 2015 and PubMed to October 2015 and cited in reviews/key publications were identified via search strings using terms relating to study design, pollutant and health outcome. Study details and estimate information were extracted and used to calculate standardised effect estimates expressed as HRs per 10 ppb increment in long-term ozone concentrations. RESULTS: 14 publications from 8 cohorts presented results for ozone and all-cause and cause-specific mortality. We found no evidence of associations between long-term annual O3 concentrations and the risk of death from all causes, cardiovascular or respiratory diseases, or lung cancer. 4 cohorts assessed ozone concentrations measured during the warm season. Summary HRs for cardiovascular and respiratory causes of death derived from 3 cohorts were 1.01 (95% CI 1.00 to 1.02) and 1.03 (95% CI 1.01 to 1.05) per 10 ppb, respectively. CONCLUSIONS: Our quantitative review revealed a paucity of independent studies regarding the associations between long-term exposure to ozone and mortality. The potential impact of climate change and increasing anthropogenic emissions of ozone precursors on ozone levels worldwide suggests further studies of the long-term effects of exposure to high ozone levels are warranted.

Chronic exposure to outdoor air pollution and lung function in adults.

BACKGROUND: The extent to which chronic exposure to outdoor air pollutants influences lung function in adults is unclear. The aim of this study was to measure the association between chronic exposure to outdoor air pollutants and adult lung function. METHODS: The relationship between measures of lung function (forced expiratory volume in 1 s (FEV(1)) and FEV(1) as a percentage of forced vital capacity (FVC)) and average exposure to particulate matter <10 microm in diameter, nitrogen dioxide, sulfur dioxide and ozone was examined in four representative cross-sectional surveys of the English population aged > or =16 in 1995, 1996, 1997 and 2001. Year-specific estimates were pooled using fixed effects meta-analysis. RESULTS: Greater exposure to particulate matter <10 microm in diameter, nitrogen dioxide and sulfur dioxide was associated with lower adult FEV(1). The size of the effect on population mean FEV(1) was about 3% for particulate matter <10 microm, and 0.7% for nitrogen dioxide and sulfur dioxide, for a 10 microg/m(3) increase in pollutant concentration. The effects were most marked in men, older adults and ex-smokers. FEV(1) was not associated with ozone concentration. No associations were found between the pollutants and FEV(1) as a percentage of FVC. CONCLUSIONS: Chronic exposure to outdoor air pollution is associated with modestly reduced FEV(1) in adults.

Emergency hospital admissions for respiratory disorders attributable to summer time ozone episodes in Great Britain.

BACKGROUND: There is accumulating evidence from various countries, including the UK, that ground level ozone concentrations are associated with increased daily hospital admissions for respiratory diseases. This paper estimates the impact of ozone episodes on daily hospital admissions for respiratory disease in Great Britain by combining locally based exposure-response relationships with mapped estimates of ozone exposure for the population in the summers of 1993 and 1995. METHODS: For the given years the available ozone measurements were used to construct maps of ozone concentrations for each day. The population exposed to a given concentration of ozone on a particular day was calculated from census data using a geographical information system. The additional hospital admissions for respiratory disease were then estimated using a regression coefficient for London. RESULTS: It is estimated that 0.10% (a total of 184) and 0.35% (a total of 643) of hospital admissions for respiratory disorders during the summers of 1993 and 1995, respectively, can be attributed to levels of ozone above 50 ppb (the recommended air quality standard for the UK). A sensitivity analysis for 1995 found that, if no threshold is assumed, the estimate is increased by about twenty fold (6% of admissions attributable). CONCLUSIONS: The additional hospital admissions for respiratory disease attributable to ozone are very small in both absolute and relative terms if a threshold of 50 ppb is assumed, but this estimate is very sensitive to threshold assumptions.