Vehicle exhaust outside the home and onset of asthma among adults

¹ Dept of Public Health and Clinical Medicine: Occupational and Environmental Medicine, Umeå University, Umeå, Sweden
² Dept of Occupational and Environmental Medicine: Respiratory Medicine and Allergology, Sahlgrenska University Hospital, Gothenburg, Sweden
³ Dept of Medical Sciences: Respiratory Medicine and Allergology, Uppsala University, Uppsala, Sweden

^* To whom correspondence should be addressed. E-mail: lars.modig{at}envmed.umu.se.

	Abstract

Few studies have investigated the relationship between vehicle exhaust and new onset of asthma among adults. The aim of this prospective cohort study was to investigate the relationship between the cumulative incidence of asthma and onset asthma among adults and vehicle exhaust concentrations at home.

Participants from three Swedish cities included in the RHINE (Respiratory Health in Northern Europe) Cohort constituted the study population. Exposure at each participant’s home was calculated using dispersion models. We also used less than 50 meter distance to nearest major road as a more simple indicator of exposure. The adjusted model included 3609 participants of which 107 were classified as onset cases and 55 as true incident cases of asthma.

There was a positive association between asthma onset (Odds Ratio, OR per 10 µg·m^-3 = 1.46, 95% Confidence Interval (CI) 1.07–1.99) and incident asthma (OR per 10 µg·m^-3 = 1.54, 95% CI 1.00–2.36) and the levels of NO₂ which remained statistically significant after adjusting for potential confounders. The relationship between asthma and NO₂ was not significantly modified by sex, hay fever or wheeze.

This study suggests that elevated levels of vehicle exhaust outside the home increase the risk of onset and incident asthma among adults.