Characteristics of peak exposure to black carbon pollution in school, commute and home environments among school children in an urban community.

Although real-time personal exposure monitoring devices have the ability to capture a wealth of data regarding fluctuations in pollutant levels, only a few studies have defined 'peaks' in black carbon (BC) exposure utilizing high-resolution data. Furthermore, studies to assess and characterize various features of peak exposure are very limited especially among children. A better understanding of characteristics of BC peak exposure would improve our understanding of health risks associated with BC. By capturing personal BC exposure at 5-min intervals using a real-time monitor during 24-hr monitoring periods among children in New York City (NYC), we defined 'peak characteristics' in 4 different ways across three major microenvironments (school vs. commute vs. home): 1) mean concentrations of BC across the 3 microenvironments, 2) 'peak duration' or time spent above the peak threshold (i.e., ≥1.5 µg/m3), 3) 'peak intensity' or the rate of exposure, defined as time spent above the threshold within each microenvironment divided by the total time spent in the microenvironment and 4) a novel metric of 'peak variability', defined as frequency of peaks (i.e., data points with +50% and -50% changes compared to the preceding and the subsequent data points), divided by the total time spent in the microenvironment. While peak duration was greatest at home, the intensity of peak exposure was greatest during commute hours, despite the short time spent in commute (p < 0.05). Peak variability was highest during commute, yet lowest in home environments (p < 0.05), particularly during non-sleeping hours. Children residing in a high-density urban setting spent on average, 5.4 hr per day above our peak threshold (≥1.5 µg/m3) in their everyday environments. Policies that limit children's exposure during high traffic periods and improved efforts to increase the number of vehicles using clean air technology could reduce the intensity of peaks and peak variability in children's BC exposure.

Personal Exposure to Black Carbon at School and Levels of Fractional Exhaled Nitric Oxide in New York City.

BACKGROUND: Schools are often located near traffic sources, leading to high levels of exposure to traffic-related air pollutants, including black carbon (BC). Thus, the school environment could play in a significant role in the adverse respiratory health of children. OBJECTIVES: Our objective was to determine associations between personal BC levels at school and airway inflammation [i.e., fractional exhaled nitric oxide (FeNO)] in school-age children. We hypothesized that higher school BC (SBC) would be associated with higher FeNO. METHODS: Children 9-14 years of age in New York City (NYC) (n=114) wore BC monitors for two 24-h periods over a 6-d sampling period, repeated 6 months later. SBC was defined as the average personal BC concentrations measured during NYC school hours (i.e., 0830-1430 hours). FeNO was measured following each 24-h BC monitoring period. Multivariable linear regression in generalized estimating equation models were used to examine associations between SBC and FeNO. Results are presented as percentage difference (PD) in FeNO. RESULTS: Personal BC at school was associated with higher FeNO (PD=7.47% higher FeNO per 1-µg/m3 BC (95% CI: 1.31, 13.9), p=0.02]. Compared with BC exposure during school, a smaller PD in FeNO was observed in association with BC exposure while commuting to and from school [PD=6.82% (95% CI: 0.70, 13.3), p=0.03]. Personal BC in non-school environments and residential BC were not associated with FeNO (p>0.05). A significant association between personal BC at school and FeNO was observed among children with seroatopy who did not have asthma [PD=21.5% (95% CI: 4.81, 40.9), p=0.01]. DISCUSSION: Schools may be important sources of BC exposure that contribute to airway inflammation in school-age children. Our results provide rationale for interventions that target improved air quality in urban schools and classrooms. https://doi.org/10.1289/EHP8985.