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

Abstract

ISEE-259 Objective: Recent cohort studies suggested that long-term exposure to air pollution is associated with mortality. The objective of the present work was to study the relation between mortality and traffic-related air pollution in a Dutch cohort study. Material and Methods: The NLCS-AIR study is part of an existing case-cohort study on diet and cancer (NLCS), which started in 1986, with ∼120,000 subjects aged 55 to 69. Individual exposure to traffic-related air pollutants was considered to be a function of a regional, urban, and local component. In addition to the default case-cohort approach of the NLCS, we also assessed the relation between mortality and air pollution in the full cohort with however limited information about confounders. Results: During the follow-up period (1987–1996) natural-cause mortality was 17,674. There were 6279 cardiovascular deaths and 1046 respiratory deaths, ie, 7325 cardiopulmonary deaths. Relative risks (RR) for the background (regional + urban) concentration for the case-cohort analyses were 1.03 (95% CI 0.91–1.17) for natural causes, 1.04 (0.90–1.20) for cardiopulmonary, 1.16 (0.91–1.48) for respiratory, and 1.03 (0.91–1.16) for noncardiopulmonary, nonlung cancer mortality for an increase in concentration of 10 μg/m3. RRs in the full cohort analyses for the same groups were 1.05 (1.00–1.10), 1.06 (0.98–1.15), 1.22 (0.99–1.49), and 1.04 (0.96–1.11). In the case-cohort analyses, the traffic intensity on the nearest road was little associated with any of the endpoints. Relative risks in the full cohort analyses for the same cause groups listed above were 1.03 (1.00–1.08), 1.06 (1.00–1.12), 1.10 (0.95–1.26), and 1.00 (0.94–1.06) for an increase of 10,000 mvh/24 h. Conclusions: These findings provide limited evidence that traffic-related air pollution increased mortality in this cohort. The findings do not confirm the high unit relative risk estimates obtained in the pilot study of this cohort.