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Background Air pollution from road traffic is a serious health hazard, and people with preexisting respiratory disease may be at increased risk. We investigated the effects of short-term exposure to diesel traffic in people with asthma in an urban, roadside environment.
Methods We recruited 60 adults with either mild or moderate asthma to participate in a randomized, crossover study. Each participant walked for 2 hours along a London street (Oxford Street) and, on a separate occasion, through a nearby park (Hyde Park). We performed detailed real-time exposure, physiological, and immunologic measurements.
Results Participants had significantly higher exposures to fine particles (<2.5 µm in aerodynamic diameter), ultrafine particles, elemental carbon, and nitrogen dioxide on Oxford Street than in Hyde Park. Walking for 2 hours on Oxford Street induced asymptomatic but consistent reductions in the forced expiratory volume in 1 second (FEV1) (up to 6.1%) and forced vital capacity (FVC) (up to 5.4%) that were significantly larger than the reductions in FEV1 and FVC after exposure in Hyde Park (P=0.04 and P=0.01, respectively, for the overall effect of exposure, and P<0.005 at some time points). The effects were greater in subjects with moderate asthma than in those with mild asthma. These changes were accompanied by increases in biomarkers of neutrophilic inflammation (sputum myeloperoxidase, 4.24 ng per milliliter after exposure in Hyde Park vs. 24.5 ng per milliliter after exposure on Oxford Street; P=0.05) and airway acidification (maximum decrease in pH, 0.04% after exposure in Hyde Park and 1.9% after exposure on Oxford Street; P=0.003). The changes were associated most consistently with exposures to ultrafine particles and elemental carbon.
Conclusions Our observations serve as a demonstration and explanation of the epidemiologic evidence that associates the degree of traffic exposure with lung function in asthma.
Source Information
From the National Heart and Lung Institute, Imperial College, and Royal Brompton Hospital (J.M., P.C., K.F.C.) and the Department of Epidemiology and Public Health, Imperial College (J.S.-E., E.M., L.J.) — all in London; the Center for Research in Environmental Epidemiology, Barcelona (M.J.N.); the University of Medicine and Dentistry of New Jersey School of Public Health, Piscataway (R.H., I.-K.H., P.O.-S., J.Z.); and the Department of Public Health Sciences, Karolinska Institutet, Stockholm (M.S.).
Address reprint requests to Dr. Cullinan at the Department of Occupational and Environmental Medicine, National Heart and Lung Institute, 1b Manresa Rd., London SW3 6LR, United Kingdom, or at p.cullinan{at}imperial.ac.uk.
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