Personal exposures to traffic-related air pollution and acute respiratory health among Bronx schoolchildren with asthma

Abstract

Background: Previous studies have reported relationships between adverse respiratory health outcomes and residential proximity to traffic pollution, but have not shown this at a personal exposure level.

Objective: We compared, among inner-city children with asthma, the associations of adverse asthma outcome incidences with increased personal exposure to particulate matter mass ≤ 2.5 μm in aerodynamic diameter (PM(2.5)) air pollution versus the diesel-related carbonaceous fraction of PM2.5.

Methods: Daily 24-hr personal samples of PM(2.5), including the elemental carbon (EC) fraction, were collected for 40 fifth-grade children with asthma at four South Bronx schools (10 children per school) during approximately 1 month each. Spirometry and symptom scores were recorded several times daily during weekdays.

Results: We found elevated same-day relative risks of wheeze [1.45; 95% confidence interval (CI), 1.03-2.04)], shortness of breath (1.41; 95% CI, 1.01-1.99), and total symptoms (1.30; 95% CI, 1.04-1.62) with an increase in personal EC, but not with personal PM(2.5) mass. We found increased risk of cough, wheeze, and total symptoms with increased 1-day lag and 2-day average personal and school-site EC. We found no significant associations with school-site PM(2.5) mass or sulfur. The EC effect estimate was robust to addition of gaseous pollutants.

Conclusion: Adverse health associations were strongest with personal measures of EC exposure, suggesting that the diesel "soot" fraction of PM(2.5) is most responsible for pollution-related asthma exacerbations among children living near roadways. Studies that rely on exposure to PM mass may underestimate PM health impacts.

Figure 1

Relative risks (RR) (with 95% CIs) of cough (A), wheeze (B), shortness of breath (C), and total symptom (D) severity scores associated with the various personal and outdoor school-site particle and gas exposure measurements. Lag EC models included predicted Sunday values from subject-specific personal-school site EC regression coefficients [except for two subjects with outlying relationships with the school-site monitor (r < 0.1)]. Because of poor correlations of personal with school-site PM_2.5, this was not feasible for PM_2.5 models. Personal EC: n = 563 for the same day; n = 571 for lag 1 day; n = 516 for 2-day average. Personal PM_2.5: n = 556 for the same day; n = 465 for lag 1-day; n = 419 for 2-day average. All school-site models: n = 625 for the same day; n = 617 for lag 1 day; n = 607 for 2-day average.

Figure 2

Relative risks (RR) (with 95% CIs) of cough (A), wheeze (B), shortness of breath (C), and total symptom (D) severity scores associated with the school-site integrated measurements of sulfur, EC, and PM_2.5. Measurements were taken from 0700 hr to 1400 hr (start hour = 7) and from 1400 hours to 0700 hours (start hour = 2). Sulfur and PM_2.5: n = 615 for 0700 hours to 1400 hours; n = 605 for 1400 hours to 0700 hours. EC: n = 635 for 0700 hours to 1400 hours; n = 625 for 1400 hours to 0700 hours. RR of total symptoms for 0700 hours to 1400 hours sulfur = 1.0 (95% CI, 0.99–1.00).