reported using the 5th to 95th percentile pol- lutant concentrations as an index of effect size on a clean day versus a polluted day. Results Table 1 lists descriptive statistics of the study subjects [for school-specific descriptive sta- tistics, see Supplemental Material, Table 1 (doi:10.1289/ehp.1002653)]. Of the 40 chil- dren enrolled in this panel, 22 were male and 18 were female. The overall mean age was 11 years, and all attended the fifth grade. All children were African American or Hispanic of Caribbean descent. Most children spent most of their time indoors (mean, 89%), came from nonsmoking households, and lived near their school, arriving at school on foot. Thirty-five of the 40 children had used medication sometime within the preceding 12 months, and 16 (of 36 reporting) had vis- ited an ED or were hospitalized for asthma symptoms within the previous year. Thirty- one subjects (of 36) reported using a “rescue” inhaler or nebulizer. Nine subjects reported using some form of controller medication. Symptom–PM analysis. Descriptive sta- tistics of personal exposure measurements are reported in the Supplemental Material (doi:10.1289/ehp.1002653). Relative risks (RRs) for symptom severity indices were at or close to statistical significance for same- day personal EC exposure concentrations. We Table 1. Subject characteristics and descriptive statistics. Characteristic All schools Age [years (mean)] 11 Sex (n) Male 22 Female 18 Subjects owning cat/dog (n) 8 Hospitalized or visited ED for asthma in 16/35 previous 12 months (n/total)a Rescue inhaler or nebulizer (n/total) 31/36 Mean afternoon PEF < 80% predicted 5/40 (n/total) Mean afternoon FEV1 < 80% predicted 14/40 (n/total) PEF, morning [L/min (mean ± SD)]b 259 ± 54 PEF, afternoon [L/min (mean ± SD)]b 271 ± 49 FEV1, morning [L (mean ± SD)]b 1.73 ± 0.37 FEV1, afternoon [L (mean ± SD)]b 1.78 ± 0.33 Daily symptom score [median (minimum– maximum) n subjects with positive symptom score per day]c Cough 6 (0–10) Wheeze 3 (0–6) Shortness of breath 3 (0–8) Total symptoms 7 (0–10)c aData missing for five subjects. bThe afternoon maneuver closest to 1500 hours (of afternoon measurements from 1200 hours to 1800 hours) was used for the analysis. If more than one measurement was taken within an hour of 1500 hours (from 1400 hr to 1600 hours) an average of the values was computed. cFor example, a given day during the study had a median of 7 of the 10 subjects having a positive symptom score, with a minimum of 0 subjects and a maximum of 10 subjects exhibiting symptoms. Environmental Health Perspectives • volume 119 | number 4 | April 2011 561 Traffic air pollution and asthma with a 2-day average personal EC concentra- tion than with either 1-day lag or same-day exposure concentrations, although CIs are also somewhat larger. Correlations of same- day personal concentrations with 1-day lag school-site concentration were relatively low for both EC (r = 0.27) and PM2.5 (r = 0.17). Lung function–PM analysis. Although none of the lung function metrics showed associations below the p < 0.05 significance threshold with any of the exposure variables evaluated in the mixed model, several rela- tionships were nearly significant (p < 0.10) for decreased lung function versus increased per- sonal pollution exposure (Table 2). We found a decrease of 9.13 L/min (95% CI, –19.02 to 0.86 L/min; p = 0.07) with increased personal EC, representing an average decline in PEF of approximately 3.5%. Although we also found an association with FEV1 decline with increased personal EC exposure, this associa- tion was not close to statistical significance. Decrements in both PEF and FEV1 were associated with increased personal PM2.5 exposure, with a decrease in PEF of 9.40 L/ min (95% CI, –20.43 to 2.08 L/min) and in FEV1 of 0.06 L (95% CI, –0.14 to 0.01 L), both representing an average decline of approximately 3.4%, with the association with FEV1 close to statistical significance. We found no significant relationships between lung function decline and any of Wheeze 2.5 2.0 R R1.5 1.0 2.5 2.0 R R1.5 1.0 found an increased risk of cough [RR = 1.23; 95% confidence interval (CI), 0.99–1.54], wheeze (RR = 1.45; 95% CI, 1.03–2.04), shortness of breath (RR = 1.41; 95% CI, 1.01–1.99) and total symptom (RR = 1.30; 95% CI, 1.04–1.61) severity per 3.0 µg/m3 EC (5th–95th percentile) concentration. We also found an increased risk for cough severity (RR = 1.37; 95% CI, 1.09–1.72) with 1-day lag personal EC concentrations. Elevated risk of cough, wheeze, and total symptom severity was significant with 2-day average concentra- tions (cough: RR = 1.61; 95% CI, 1.17–2.21; wheeze: RR = 1.67; 95% CI, 1.05–2.66; total symptoms: RR = 1.54; 95% CI, 1.13–2.10) (Figure 1). We did not find an increased risk of any of the symptom outcomes from increased exposure to personal PM2.5 with same-day, 1-day lag, or 2-day average concentrations. An increased risk of cough severity (RR = 1.28; 95% CI, 1.06–1.54) was significantly associated with 1-day lag school-site EC. With a 2-day average concentration, school- site EC was also associated with an elevated risk of cough severity (RR = 1.32; 95% CI, 1.05–1.66) and total symptom severity (RR = 1.24; 95% CI, .99–1.56) (Figure 1). We found no statistically significant relationships of increased risk of symptoms with any of the other school-site PM measurements, although RR effect estimates were all > 1.0. Except for shortness of breath, RR estimates were larger Cough Lag 0 Lag 1 2-day average 2.5 2.0 R R1.5 1.0 2.5 2.0 R R1.5 1.0 PersonaPleErCsonalPMSc2h.5ool-siteEC School-site PM2.5 Rooftop PSMch2.o5ol-site NO2 teO3 School-si Shortness of breath PersonaPleErCsonalPMSc2h.5ool-siteEC School-site PM2.5 Rooftop PSMch2.o5ol-site NO2 teO3 School-si Total symptoms NO2 School-si PSMch2.o5ol-site PersonaPleErCsonalPMSc2h.5ool-siteEC PersonaPleErCsonalPMSc2h.5ool-siteEC PM2.5 teO3 PM2.5 teO3 School-site Rooftop School-site Rooftop 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 PM2.5, this was not feasible for PM2.5 models. Personal EC: n = 563 for the same day; n = 571 for lag 1 day; n = 516 for 2-day average. Personal PM2.5: 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. PSMch2.o5ol-site NO2 School-si