Previously published studies have found associations between residence in high air pollution areas within the Los Angeles area and decreased lung development.1,–3 Investigators from the University of Southern California, Los Angeles, the University of California, Berkeley, and their collaborators from Petaluma, California and Barcelona, Spain, sought to assess whether proximity to major roadways adversely affects lung-function growth in children between ages 10 and 18, a period of rapid growth and rapid lung development.
Study participants were part of the Children’s Health Study that recruited two cohorts of fourth-grade children from 12 southern California communities with a wide range in regional air quality. Children in both cohorts were prospectively followed up for eight years. Children had yearly lung-function measurements. A yearly questionnaire was used to update information on asthma status, personal smoking, and exposure to environmental tobacco smoke.
The exposure of every study participant to traffic-related pollutants was characterized by two types of measures — proximity of the child’s residence to the nearest freeway or to the nearest major nonfreeway road, and model-based estimates of traffic-related air pollution at the residence, derived from dispersion models that incorporated distance to roadways, vehicle counts, vehicle emission rates, and meteorological conditions. Regional air pollution was continuously monitored at one central site location within each study community over the course of the investigation.
A total of 3,677 children with a mean age of 10 years (SD=0.44) were enrolled (cohort 1, n=1,718; cohort 2, n=1,959). There were equal proportions of male and female participants. Most children were of nonHispanic white or Hispanic ethnic origin; 440 (12%) children lived within 500 m of a freeway.
An average of 6.2 pulmonary function tests were done per child. Eight-year growth in forced expiratory volume (FEV1), and maximum midexpiratory flow rate (MMEF) averaged 1316 mL and 1402 mL/s, respectively, in girls, and 2406 mL and 2476 mL/s, respectively, in boys. Reduced lung-function growth was independently associated with both freeway distance and regional air pollution. Children living within 500 m of a freeway (−81 mL; 95% CI, −143 had deficits in eight-year growth of FEV1 to −18) and MMEF (−127 mL/s; 95% CI, −243 to −11) compared with those living at least 1500 m from a freeway. Even children in low air pollution regions had negative effects when living <500 m from freeways. For children living within 500 m of freeways, the average deficits in attained mean-percent-predicted lung function at age 18, relative to children living >1500 m from freeways, were 97.0% for FEV1 (P=.013; 95% CI, 94.6–99.4) and 93.4% for MMEF (P=.006; 95% CI, 89.1–97.7).
Nonstatistically significant decreases also were found among children living at intermediate ranges from a freeway suggesting a dose response relationship. Such effects were not found for other large...