Passive measurement of nitrogen oxides to assess traffic-related pollutant exposure for the East Bay Children's Respiratory Health Study

Abstract

The East Bay Children's Respiratory Health Study is examining associations between trafficrelated pollutant exposures and respiratory health among children who reside and attend schools at varied proximity to northern California freeways. Chronic exposures are being inferred from outdoor pollutant concentrations at neighborhood schools. This paper reports primarily weeklong integrated NO 2 and NO X concentrations measured with passive samplers placed outside at ten elementary schools during 14 weeks in spring and 8 weeks in fall 2001. Measurements were also made outside selected student residences to examine spatial variability within three school neighborhoods. Regional concentrations of NO 2 and NO X varied widely from week to week.School site data were normalized to measurements at a nearby regional monitoring station to facilitate analysis of relative pollutant exposures at the neighborhood schools. Normalized concentrations occurred at a school located directly adjacent to a major freeway and a shopping center. In this case, normalized NO 2 and NO X were ~60% and ~100% higher than regional background levels. At three schools within 130-230 m downwind of a freeway, normalized NO 2 and NO X were ~20-30% and ~50-80% higher than regional levels. Validation testing of the passive samplers indicated precision of better than 5% for both NO 2 and NO X when samplers were deployed outside for one-week periods. Passive sampler results agreed with co-located chemiluminescence measurements to within 8% for NO 2 and 3% for NO X .

Passive Sampling of Ambient Nitrogen Dioxide at Toll Plazas in Malaysia

“…Indoor NO 2 concentrations reported for office [55] and resident [31] micro-environments were consistent with levels of theindoor NO 2 measure at Puta-Makhota toll plazas, while NO 2 concentrations at Sungai Besi and Kajang Toll plazas exceeded those reported in other studies by 3 to 4 times [20] [56]. The reason for such levels of pollution at toll plazas is possibly due to high levels of traffic density congestion which would rarely be found in residential areas.…”

“…Meteorological factors such as wind, precipitation, humidity and temperature, influence the dispersion, deposition, transportation and transformation of nitrogen dioxide. Wind direction defines the direction of pollutant spatial distribution, while wind speed dictates the dispersion and deposition rate [19] [20]. High wind speed tends to reduce NO 2 concentration by aiding pollutant transportation and dispersion and vice versa in the direction of up-wind [21] [22].…”

Traffic-related Air Pollution near Busy Roads

“…We found that the rank order (relative values) of the schools did not vary from week to week or season to season, supporting the validity of this approach. Additionally, the NO x and NO 2 concentrations at schools upwind or further from high traffic roads were similar to NO X and NO 2 concentrations measured at the closest fixed-site monitor (21). Although there may have been some changes in the absolute traffic volume on major roads in recent years, the principal traffic patterns in the area have not changed.…”

“…The study average PM 2.5 (12 g/m 3 ) was similar to the annual average concentration of PM 2.5 at the central monitoring station, located approximately 15 km south of the study area. NO X and NO 2 measurements at the school sites away from traffic were similar to levels measured at the regional site (21). Table 3 summarizes the results of the two-stage hierarchical logistic regression models of the odds of asthma and bronchitis symptoms in the previous year in relationship to six different pollutants, each examined in separate regressions.…”

“…Study-averaged air pollution concentrations were calculated at each school by first normalizing the data to account for occasional missing values. Additional details are described in the online supplement and elsewhere (21). In preliminary analyses, we also used school location in relationship to prevailing winds and proximity to busy roads as an additional traffic metric.…”