Outdoor Environment and Pediatric Asthma: An Update on the Evidence from North America

Table 1

Studies focused on traffic-related air pollution (TRAP).

Source/year	Outdoor variables	Age group	Sample size	Climate region	Study design	Assessment method	Findings and limits
Asthma symptom
Bernstein, 2012	TRAP (ECAT)	1–7 years	700	Central, US	Cohort/adjusted	Medical evaluations, skin testing, proximity, and LUR	Higher TRAP associated with wheezing during infancy and at age 3. Limit: parental reports of wheezing at 3 are not strong asthma predictors
McConnell et al., 2010	TRAP, PM10, PPM2.5, O3	K-1st grade	2,497	Western, US	Cohort/adjusted	Baseline and annual questionnaires, community ambient air pollution, weather variables, local TRAP	Asthma risk increased with modeled TRAP from roadway near home (HR 1.51; 95% CI: 1.25–1.82) and near school (HR 1.45; 95% CI: 1.06–1.98). Limit: short 3-year follow-up
Sucharew et al., 2010	TRAP, PM10, PM2.5,	1–3 years	550	Central, US	Cohort/adjusted	Questionnaires, skin prick test, air quality monitoring, clinical evaluation, home visits, house dust	Children exposed to higher levels of TRAP are more likely to suffer recurrent night cough (OR, 1.45, 95% CI, 1.09–1.94) than children less exposed. Limit: sample is limited to those with high risk
Eckel et al., 2011	TRAP, roads, traffic densities, NO, NO2	7–11 years	2,143	Western, US	Cross-sectional/adjusted	Breath collection technique (offline and online), geocoding distance from residence to roads, road class, and density data, NO2 sampling/, questionnaire, body mass index,	Length of roads positively was associated with FeNO, with significant associations in small buffers: 46.7% [95% CI, 14.3–88.4] higher FeNO for increases in the length of all roads in 50 m buffers. Limit: rely on parent report for medication use as a confounding factor
Asthma-related symptom and care utilization
Newman et al., 2014	TRAP	1–16 years	758	Central, US	Cohort/adjusted	Administrative data (ICD-9-CM) for hospital readmission (primary or secondary diagnosis), questionnaires, serum sample, allergen-specific IgE testing	Higher TRAP exposure was associated with higher readmission rate (21% versus 16%; ), association was not significant after adjusting for covariates (aOR, 1.4; 95% CI, 0.9–2.2). Limit: sample was from one single institution

aOR: adjusted Odds Ratio; HR: Hazard Ratio; LUR: land use regression; ECAT: elemental carbon attributed to traffic. Note. (a) TRAP exposure estimated using a qualitative proximity model and quantitative LUR model; (b) modeled annual concentration estimates based on surrounding area characteristics (c) used several models including line source dispersion and regression models to map estimates.