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. 2013 Mar;121(3):324-31.
doi: 10.1289/ehp.1205862. Epub 2013 Jan 8.

Long-term Exposure to Urban Air Pollution and Mortality in a Cohort of More Than a Million Adults in Rome

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Long-term Exposure to Urban Air Pollution and Mortality in a Cohort of More Than a Million Adults in Rome

Giulia Cesaroni et al. Environ Health Perspect. .
Free PMC article


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.

Conflict of interest statement

The authors declare they have no actual or potential competing financial interests.


Figure 1
Figure 1
Maps of the concentrations of PM2.5 (A) and NO2 (B) in Rome. The NO2 map (adapted from Cesaroni et al. 2012a) was obtained using a natural neighbor interpolation method of all the estimated values at the study population’s residential addresses.
Figure 2
Figure 2
Estimated concentration–response curves (solid lines) and 95% CIs (dashed lines) for nonaccidental causes, cardiovascular disease, IHD, and lung cancer for NO2 (A) and PM2.5 (B). Cox models adjusted for sex, marital status, place of birth, education, occupation, and area-based socioeconomic position on a 20% sample of the cohort.
Figure 3
Figure 3
Adjusted HRs (95% CIs) and p-values for interaction for cause-specific mortality per 10‑µg/m3 elevation in NO2 (A) and PM2.5 concentrations (B), by population characteristics and cause of death.

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