title: The relevance of commuter and work/school exposure in an epidemiological study on traffic-related air pollution.
abstract: Exposure during transport and at non-residential locations is ignored in most epidemiological studies of traffic-related air pollution. We investigated the impact of separately estimating NO2 long-term outdoor exposures at home, work/school, and while commuting on the association between this marker of exposure and potential health outcomes. We used spatially and temporally resolved commuter route data and model-based NO2 estimates of a population sample in Basel, Switzerland, to assign individual NO2-exposure estimates of increasing complexity, namely (1) home outdoor concentration; (2) time-weighted home and work/school concentrations; and (3) time-weighted concentration incorporating home, work/school and commute. On the basis of their covariance structure, we estimated the expectable relative differences in the regression slopes between a quantitative health outcome and our measures of individual NO2 exposure using a standard measurement error model. The traditional use of home outdoor NO2 alone indicated a 12% (95% CI: 11-14%) underestimation of related health effects as compared with integrating both home and work/school outdoor concentrations. Mean contribution of commuting to total weekly exposure was small (3.2%; range 0.1-13.5%). Thus, ignoring commute in the total population may not significantly underestimate health effects as compared with the model combining home and work/school. For individuals commuting between Basel-City and Basel-Country, ignoring commute may produce, however, a significant attenuation bias of 4% (95% CI: 4-5%). Our results illustrate the importance of including work/school locations in assessments of long-term exposures to traffic-related air pollutants such as NO2. Information on individuals' commuting behavior may further improve exposure estimates, especially for subjects having lengthy commutes along major transportation routes.
authors.affiliation: 1] Swiss Tropical and Public Health Institute, Basel, Switzerland [2] University of Basel, Basel, Switzerland.
authors.forename: Martina S
authors.initials: MS
authors.lastname: Ragettli
authors.affiliation: 1] Swiss Tropical and Public Health Institute, Basel, Switzerland [2] University of Basel, Basel, Switzerland [3] Centre for Environmental Science and Engineering, Indian Institute of Technology Bombay, Mumbai, India.
authors.forename: Harish C
authors.initials: HC
authors.lastname: Phuleria
authors.affiliation: 1] Swiss Tropical and Public Health Institute, Basel, Switzerland [2] University of Basel, Basel, Switzerland.
authors.forename: Ming-Yi
authors.initials: MY
authors.lastname: Tsai
authors.affiliation: 1] Swiss Tropical and Public Health Institute, Basel, Switzerland [2] University of Basel, Basel, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Schindler
authors.affiliation: Centre for Environmental Policy, Imperial College, London, UK.
authors.forename: Audrey
authors.initials: A
authors.lastname: de Nazelle
authors.affiliation: 1] Swiss Tropical and Public Health Institute, Basel, Switzerland [2] University of Basel, Basel, Switzerland.
authors.forename: Regina E
authors.initials: RE
authors.lastname: Ducret-Stich
authors.affiliation: 1] Swiss Tropical and Public Health Institute, Basel, Switzerland [2] University of Basel, Basel, Switzerland.
authors.forename: Alex
authors.initials: A
authors.lastname: Ineichen
authors.affiliation: 1] Swiss Tropical and Public Health Institute, Basel, Switzerland [2] University of Basel, Basel, Switzerland.
authors.forename: Laura
authors.initials: L
authors.lastname: Perez
authors.affiliation: 1] Swiss Tropical and Public Health Institute, Basel, Switzerland [2] University of Basel, Basel, Switzerland.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Braun-Fahrländer
authors.affiliation: 1] Swiss Tropical and Public Health Institute, Basel, Switzerland [2] University of Basel, Basel, Switzerland.
authors.forename: Nicole
authors.initials: N
authors.lastname: Probst-Hensch
authors.affiliation: 1] Swiss Tropical and Public Health Institute, Basel, Switzerland [2] University of Basel, Basel, Switzerland.
authors.forename: Nino
authors.initials: N
authors.lastname: Künzli
mesh_terms: D000293:Adolescent; D000328:Adult; D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000032:analysis*; D001642:Bicycling; D004781:Environmental Exposure / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods*; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008171:Lung Diseases / Q000139:chemically induced / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009585:Nitrogen Dioxide / Q000032:analysis*; D016273:Occupational Exposure / Q000032:analysis; D012044:Regression Analysis; D018570:Risk Assessment / Q000379:methods*; D012574:Schools; D062211:Spatio-Temporal Analysis; D013557:Switzerland / Q000453:epidemiology; D013997:Time Factors; D014186:Transportation; D014505:Urban Population; D016138:Walking; D014937:Work; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D009585:Nitrogen Dioxide