We used data from 22 European cohort studies, which created a total study population of 367鈥?51 participants. All cohorts were general population samples, although some were restricted to one sex only. With a strictly standardised protocol, we assessed residential exposure to air pollutants as annual average concentrations of particulate matter (PM) with diameters of less than 2路5 渭m (PM<sub>2路5sub>), less than 10 渭m (PM<sub>10sub>), and between 10 渭m and 2路5 渭m (PM<sub>coarsesub>), PM<sub>2.5sub> absorbance, and annual average concentrations of nitrogen oxides (NO<sub>2sub> and NO<sub>xsub>), with land use regression models. We also investigated two traffic intensity variables鈥攖raffic intensity on the nearest road (vehicles per day) and total traffic load on all major roads within a 100 m buffer. We did cohort-specific statistical analyses using confounder models with increasing adjustment for confounder variables, and Cox proportional hazards models with a common protocol. We obtained pooled effect estimates through a random-effects meta-analysis.
The total study population consisted of 367鈥?51 participants who contributed 5鈥?18鈥?39 person-years at risk (average follow-up 13路9 years), of whom 29鈥?76 died from a natural cause during follow-up. A significantly increased hazard ratio (HR) for PM<sub>2路5sub> of 1路07 (95% CI 1路02-1路13) per 5 渭g/m<sup>3sup> was recorded. No heterogeneity was noted between individual cohort effect estimates (I<sup>2sup> p value=0路95). HRs for PM<sub>2路5sub> remained significantly raised even when we included only participants exposed to pollutant concentrations lower than the European annual mean limit value of 25 渭g/m<sup>3sup> (HR 1路06, 95% CI 1路00-1路12) or below 20 渭g/m<sup>3sup> (1路07, 1路01-1路13).
Long-term exposure to fine particulate air pollution was associated with natural-cause mortality, even within concentration ranges well below the present European annual mean limit value.
European Community's Seventh Framework Program (FP7/2007-2011).