Acute cardiorespiratory health effects of size-segregated ambient particulate air pollution and ozone

Ambient air pollutants are one of the most harmful environmental stressors to human health. During the last decades, different ambient particulate and gaseous pollutants have been studied, and in numerous studies fine particles (< 2.5 μm in aerodynamic diameter, PM2.5) and larger, inhalable particles (< 10 μm, PM10) have been associated with excess morbidity and mortality. Particle size and composition are likely to affect the toxicity of particles. The composition of particles varies as they are emitted from different sources. However, the health effects of different types of ambient particles have rarely been determined because of the lack of measurement data. The aim of this thesis was to study the components of ambient air pollution that may explain the short-term health effects associated with the changes in the levels of air pollution. Particles in different size fractions, gaseous pollutants such as ozone (O3), nitrogen dioxide (NO2), and carbon monoxide (CO), and PM2.5 emitted from different sources were studied. The health effects studied were cause-specified daily mortality and hospital admissions for cardiorespiratory causes, and emergency room visits for asthma and chronic obstructive pulmonary disease (COPD). To establish possible differences in the sensitivity to air pollutants, the analyses were done separately for three age groups: children under 15 years of age, adults aged 15–64 years, and the elderly aged 65 years or older. All the data was collected during 1998–2004 from Helsinki metropolitan area, which consists of four municipalities: Helsinki, Vantaa, Espoo and Kauniainen. Mass and count of ambient particles and concentrations of gaseous pollutants were measured at central measurement sites in Helsinki, except for O3 that was monitored at a suburban station. Fine particulate mass (PM2.5) was apportioned between four sources: traffic, longrange transport, soil, and coal/oil combustion. Daily mortality, hospital admission, and emergency room visit counts were obtained from national registers. The mean (SD) daily levels of PM2.5 in Helsinki were 9 (5.8) μg/m 3. More than half of the PM2.5 mass was long-range transported, a fifth was from local traffic, and the rest was from soil, coal/oil combustion, and unidentified sources. The mean (SD) counts of ultrafine particles (UFP, < 0.1 μm) and accumulation mode particles (0.1–0.3 μm) were 8 203 (5 137) and, 359 (261) 1/cm3, respectively. The mean (SD) concentration of coarse particles (2.5–10 μm), NO2, CO, and O3 were 9.9 (8.3) μg/m 3, 28 (11.3) μg/m3, 0.5 (0.2) mg/m3, and 71 (20) μg/m3, respectively. Increases in daily levels of traffic-related pollutants (UFP, NO2, CO) and O3 were associated with increased asthma emergency room visits among children. Among the elderly, especially accumulation mode particles and PM2.5, but also coarse particles, were associated with all respiratory, pneumonia and pooled asthma-COPD morbidity. Trafficrelated and long-range transported PM2.5, but also PM2.5 from soil was associated with the respiratory morbidity of the elderly. Among children, the associations with ultrafine particles had a delay of 3–5 days, whereas among the elderly the associations were more immediate. Pooled asthma-COPD hospital admissions of the elderly were also increased in association with O3. Few associations were observed among adults. Overall, few associations between cardiovascular outcomes and ambient pollutants were observed. However, total cardiovascular and stroke mortality, but not stroke morbidity, among the elderly was associated with the increase in PM2.5 during the warm season. There was also some suggestion of an association between arrhythmia admissions and PM2.5. The current results agree with earlier studies showing the effect of particulate air pollution and ozone on increased daily respiratory mortality and morbidity. Although few associations were observed for cardiovascular outcomes in the present study, these results together with results from earlier international studies and Finnish panel studies suggest the importance of particulate air pollution also in Helsinki, especially among individuals with underlying cardiorespiratory disease. Accumulation mode particles and PM2.5 have more associations with different outcomes than other particle fractions. This may partly be due to better exposure assessment of these particles compared to ultrafine and coarse particles. Of the PM2.5 sources, traffic and long-range transported PM2.5 have the strongest effects on respiratory health, but also soil-derived particles seem to be harmful. Ultrafine particles and NO2 are considered as markers of traffic pollutants, and in this study, it was not possible to identify the causal component of traffic emissions responsible for the observed effects among children. Overall, adults seem to be less sensitive to the effects of ambient pollutants than children and the elderly. In summary, the effects of ambient pollutants are clearer on respiratory than on cardiovascular health, and among children and the elderly than among adults, in Helsinki. Although some differences were observed in the health effects of different particle size fractions and PM2.5 from different sources, they all appear capable of causing adverse health effects. These results underline the importance of particulate matter together with ozone as a main environmental threat to health also in Helsinki. Keywords; air pollution, cardiovascular, emergency room visit, epidemiology, hospital admission, mortality, respiratory, particulate matter, particulate number Jaana Halonen, Kokoluokiteltujen ulkoilman hiukkasten seka otsonin akuutit vaikutukset verenkiertoja hengityselimiston terveyteen Terveyden ja hyvinvoinnin laitoksen julkaisuja, Tutkimus 19|2009, 174 sivua ISBN 978-952-245-112-5 (painettu); ISBN 978-952-245-113-2 (pdf) ISSN 1798-0054 (painettu); ISSN 1798-0062 (pdf)