Traffic Exposure Increases Mortality from Many Causes

Long-Term Effects of Traffic-Related Air Pollution on Mortality
in a Dutch Cohort (NLCS-AIR Study)

Rob Beelen,1 Gerard Hoek,1 Piet A. van den Brandt,2 R. Alexandra Goldbohm,3 Paul Fischer,4 Leo J. Schouten,2
Michael Jerrett,5 Edward Hughes,6 Ben Armstrong,7 and Bert Brunekreef1,8
1Institute for Risk Assessment Sciences, Division Environmental Epidemiology, Utrecht University, Utrecht, the Netherlands; 2Department
of Epidemiology, Maastricht University, Maastricht, the Netherlands; 3TNO Quality of Life, Department of Prevention and Health, Leiden,
the Netherlands; 4Centre for Environmental Health Research, National Institute for Public Health and the Environment (RIVM), Bilthoven,
the Netherlands; 5School of Public Health, University of California, Berkeley, California, USA; 6Edward Hughes Consulting, Ottawa, Ontario,
Canada; 7Public and Environmental Research Unit, London School of Hygiene and Tropical Medicine, London, United Kingdom; 8Julius
Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, the Netherlands

BACKGROUND: Several studies have found an effect on mortality of between-city contrasts in
long-term exposure to air pollution. The effect of within-city contrasts is still poorly understood.
OBJECTIVES: We studied the association between long-term exposure to traffic-related air pollution and mortality in a Dutch cohort.
METHODS: We used data from an ongoing cohort study on diet and cancer with 120,852 subjects who were followed from 1987 to 1996. Exposure to black smoke (BS), nitrogen dioxide, sulfur dioxide, and particulate matter ≤ 2.5 μm (PM2.5), as well as various exposure variables related to traffic, were estimated at the home address. We conducted Cox analyses in the full cohort adjusting for age, sex, smoking, and area-level socioeconomic status.

RESULTS: Traffic intensity on the nearest road was independently associated with mortality.
Relative risks (95% confidence intervals) for a 10-μg/m3 increase in BS concentrations (difference between 5th and 95th percentile) were 1.05 (1.00–1.11) for natural cause, 1.04 (0.95–1.13) for cardiovascular, 1.22 (0.99–1.50) for respiratory, 1.03 (0.88–1.20) for lung cancer, and 1.04 (0.97–1.12) for mortality other than cardiovascular, respiratory, or lung cancer. Results were similar for NO2 and PM2.5, but no associations were found for SO2.
CONCLUSIONS: Traffic-related air pollution and several traffic exposure variables were associated with
mortality in the full cohort. Relative risks were generally small. Associations between natural-cause and respiratory mortality were statistically significant for NO2 and BS. These results add to the evidence that long-term exposure to ambient air pollution is associated with increased mortality.
KEY WORDS: air pollution, cohort, mortality, traffic. Environ Health Perspect 116:196–202 (2008).