Long-Term Exposure to Urban Air Pollution and Mortality in a Cohort of More than a Million Adults in Rome
Giulia Cesaroni,1 Chiara Badaloni,1 Claudio Gariazzo,2 Massimo Stafoggia,1 Roberto Sozzi,3 Marina Davoli,1 and Francesco Forastiere1
1Department of Epidemiology, Lazio Regional Health Service, Rome, Italy; 2Italian Workers’ Compensation Authority (INAIL), Rome, Italy; 3Regional Environmental Protection Agency, Rome, Italy
Background: Few European studies have investigated the effects of long-term exposure to both fine particulate matter (≤ 2.5 µm; PM2.5) and nitrogen dioxide (NO2) on mortality.
Objectives: We studied the association of exposure to NO2, PM2.5, and traffic indicators on cause-specific mortality to evaluate the form of the concentration–response relationship.
Methods: We analyzed a population-based cohort enrolled at the 2001 Italian census with 9 years of follow-up. We selected all 1,265,058 subjects ≥ 30 years of age who had been living in Rome for at least 5 years at baseline. Residential exposures included annual NO2 (from a land use regression model) and annual PM2.5 (from a Eulerian dispersion model), as well as distance to roads with > 10,000 vehicles/day and traffic intensity. We used Cox regression models to estimate associations with cause-specific mortality adjusted for individual (sex, age, place of birth, residential history, marital status, education, occupation) and area (socioeconomic status, clustering) characteristics.
Results: Long-term exposures to both NO2 and PM2.5 were associated with an increase in nonaccidental mortality [hazard ratio (HR) = 1.03 (95% CI: 1.02, 1.03) per 10-µg/m3 NO2; HR = 1.04 (95% CI: 1.03, 1.05) per 10-µg/m3 PM2.5]. The strongest association was found for ischemic heart diseases (IHD) [HR = 1.10 (95% CI: 1.06, 1.13) per 10-µg/m3 PM2.5], followed by cardiovascular diseases and lung cancer. The only association showing some deviation from linearity was that between NO2 and IHD. In a bi-pollutant model, the estimated effect of NO2 on mortality was independent of PM2.5.
Conclusions: This large study strongly supports an effect of long-term exposure to NO2 and PM2.5 on mortality, especially from cardiovascular causes. The results are relevant for the next European policy decisions regarding air quality.
Key words: air pollution, cardiovascular mortality, fine particulate matter, ischemic heart disease, lung cancer, mortality, nitrogen dioxide.
Environ Health Perspect 121:324–331 (2013). http://dx.doi.org/10.1289/ehp.1205862 [Online 8 January 2013]
Address correspondence to G. Cesaroni, Department of Epidemiology of Lazio Regional Health Service, Via di S.Costanza 53, 00198 Rome, Italy. Telephone: 390683060462. E-mail: firstname.lastname@example.org
Supplemental Material is available online (http://dx.doi.org/10.1289/ehp.1205862).
We thank M. Becker for her help in editing the manuscript, V. Belleudi and G. Cappai for their support in record linkage procedures, C. Tasco for her commitment in including this study as part of the National Statistical Programme, C. Perrino for providing data for validation of the PM2.5 model, and D. Consonni for his help in STATA scripts for time-dependent analyses.
The authors declare they have no actual or potential competing financial interests.
Received 6 August 2012; Accepted 7 January 2013; Online 8 January 2013.
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