Air pollution and nonmalignant respiratory mortality in 16 cohorts within the ESCAPE project

Abstract

Rationale: Prospective cohort studies have shown that chronic exposure to particulate matter and traffic-related air pollution is associated with reduced survival. However, the effects on nonmalignant respiratory mortality are less studied, and the data reported are less consistent.

Objectives: We have investigated the relationship of long-term exposure to air pollution and nonmalignant respiratory mortality in 16 cohorts with individual level data within the multicenter European Study of Cohorts for Air Pollution Effects (ESCAPE).

Methods: Data from 16 ongoing cohort studies from Europe were used. The total number of subjects was 307,553. There were 1,559 respiratory deaths during follow-up.

Measurements and main results: Air pollution exposure was estimated by land use regression models at the baseline residential addresses of study participants and traffic-proximity variables were derived from geographical databases following a standardized procedure within the ESCAPE study. Cohort-specific hazard ratios obtained by Cox proportional hazard models from standardized individual cohort analyses were combined using metaanalyses. We found no significant associations between air pollution exposure and nonmalignant respiratory mortality. Most hazard ratios were slightly below unity, with the exception of the traffic-proximity indicators.

Conclusions: In this study of 16 cohorts, there was no association between air pollution exposure and nonmalignant respiratory mortality.

Figure 1.

Location of all cohorts. Circles mark the cohort areas in which both particulate matter (PM) and nitrogen oxides were measured. Squares indicate cohort areas where only NO₂ and nitrogen oxides (NO_x) were measured.

Figure 2.

Description of modeled outdoor concentrations of NO₂ (a) and particulate matter with an aerodynamic diameter < 2.5 μm (PM_2.5) (μg/m³) (b) at participant addresses in each cohort. Particulate matter data not available for EPIC-Umeå.

Figure 3.

Description of traffic intensity on the nearest road (motor vehicles/d) (a) and traffic load on major roads in a 100-m buffer (motor vehicles × m/d) (b) at participant addresses in each cohort.

Figure 4.

Cohort-specific and pooled hazard ratios (HRs) and 95% confidence intervals (CIs) based on confounder model 3 for nonmalignant respiratory mortality in association with NO₂ (per 10 μg/m³) (a) and particulate matter with an aerodynamic diameter < 2.5 μm (PM_2.5) (per 5 μg/m³) (b) modeled outdoor concentrations. Model 3: gender, calendar time + smoking status, smoking intensity, smoking duration, environmental tobacco smoke, occupation, employment status, intake of fruit, intake of vegetables, marital status, educational level, body mass index + socioeconomic status at an area level (i.e., of the municipality or neighborhood).

Figure 5.

Cohort-specific and pooled hazard ratios (HRs) and 95% confidence intervals (CIs) based on confounder model 3 for nonmalignant respiratory mortality in association with total traffic load on all major roads within a 100-m buffer (4,000,000 motor vehicles × m/d) around the subjects’ residences (a) and with traffic intensity on the nearest road (per 5,000 motor vehicles/d) (b). Model 3: gender, calendar time + smoking status, smoking intensity, smoking duration, environmental tobacco smoke, occupation, employment status, intake of fruit, intake of vegetables, marital status, educational level, body mass index + socioeconomic status at an area level (i.e., of the municipality or neighborhood).