The effects of urban green space and road proximity to indoor traffic-related PM2.5, NO2, and BC exposure in inner-city schools.

BACKGROUND: Since there are known adverse health impacts of traffic-related air pollution, while at the same time there are potential health benefits from greenness, it is important to examine more closely the impacts of these factors on indoor air quality in urban schools. OBJECTIVE: This study investigates the association of road proximity and urban greenness to indoor traffic-related fine particulate matter (PM2.5), nitrogen dioxide (NO2), and black carbon (BC) in inner-city schools. METHODS: PM2.5, NO2, and BC were measured indoors at 74 schools and outdoors at a central urban over a 10-year period. Seasonal urban greenness was estimated using the Normalized Difference Vegetation Index (NDVI) with 270 and 1230 m buffers. The associations between indoor traffic-related air pollution and road proximity and greenness were investigated with mixed-effects models. RESULTS: The analysis showed linear decays of indoor traffic-related PM2.5, NO2, and BC by 60%, 35%, and 22%, respectively for schools located at a greater distance from major roads. The results further showed that surrounding school greenness at 270 m buffer was significantly associated (p < 0.05) with lower indoor traffic-related PM2.5: -0.068 (95% CI: -0.124, -0.013), NO2: -0.139 (95% CI: -0.185, -0.092), and BC: -0.060 (95% CI: -0.115, -0.005). These associations were stronger for surrounding greenness at a greater distance from the schools (buffer 1230 m) PM2.5: -0.101 (95% CI: -0.156, -0.046) NO2: -0.122 (95% CI: -0.169, -0.075) BC: -0.080 (95% CI: -0.136, -0.026). These inverse associations were stronger after fully adjusting for regional pollution and meteorological conditions. IMPACT STATEMENT: More than 90% of children under the age of 15 worldwide are exposed to elevated air pollution levels exceeding the WHO's guidelines. The study investigates the impact that urban infrastructure and greenness, in particular green areas and road proximity, have on indoor exposures to traffic-related PM2.5, NO2, and BC in inner-city schools. By examining a 10-year period the study provides insights for air quality management, into how road proximity and greenness at different buffers from the school locations can affect indoor exposure.

Laboratory and field evaluation of measurement methods for one-hour exposures to O3, PM2.5, and CO.

While researchers have linked acute (less than 12-hr) ambient O3, PM2.5, and CO concentrations to a variety of adverse health effects, few studies have characterized short-term exposures to these air pollutants, in part due to the lack of sensitive, accurate, and precise sampling technologies. In this paper, we present results from the laboratory and field evaluation of several new (or modified) samplers used in the "roll-around" system (RAS), which was developed to measure 1-hr O3, PM2.5, and CO exposures simultaneously. All the field evaluation data were collected during two sampling seasons: the summer of 1998 and the winter of 1999. To measure 1-hr O3 exposures, a new active O3 sampler was developed that uses two nitrite-coated filters to measure O3 concentrations. Laboratory chamber tests found that the active O3 sampler performed extremely well, with a collection efficiency of 0.96 that did not vary with temperature or relative humidity (RH). In field collocation comparisons with a reference UV photometric monitor, the active O3 sampler had an effective collection efficiency ranging between 0.92 and 0.96 and a precision for 1-hr measurements ranging between 4 and 6 parts per billion (ppb). The limits of detection (LOD) of this method were 9 ppb-hr for the chamber tests and approximtely 16 ppb-hr for the field comparison tests. PM2.5 and CO concentrations were measured using modified continuous monitors--the DustTrak and the Langan, respectively. A size-selective inlet and a Nafion dryer were placed upstream of the DustTrak inlet to remove particles with aerodynamic diameters greater than 2.5 microm and to dry particles prior to the measurements, respectively. During the field validation tests, the DustTrak consistently reported higher PM2.5 concentrations than those obtained by the collocated 12-hr PM2.5 PEM samples, by approximately a factor of 2. After the DustTrak response was corrected (correction factor of 2.07 in the summer and 2.02 in the winter), measurements obtained using these methods agreed well with R2 values of 0.87 in the summer and 0.81 in the winter. The results showed that the DustTrak can be used along with integrated measurements to measure the temporal and spatial variation in PM2.5 exposures. Finally, during the field validation tests, CO concentrations measured using the Langan were strongly correlated with those obtained using the reference method when the CO levels were above the LOD of the instrument [approximately 1 part per million (ppm)].

Mechanisms of morbidity and mortality from exposure to ambient air particles.

The studies reported here assessed pathophysiologic mechanisms that result from exposure to concentrated ambient particles (CAPs) in animals with and without cardiopulmonary compromise. These studies were carried out to determine the biologic plausibility of epidemiologic observations of increases in particulate air pollution associated with increases in human morbidity and mortality. Dogs were exposed two at a time to CAPs or filtered air via tracheostomy for six hours per day on three consecutive days. The electrocardiogram (ECG) and breathing pattern were recorded continuously, and indicators of inflammation were also assessed. In one experimental design, normal dogs were exposed in pairs to CAPs and subsequently to filtered air or to filtered air and subsequently CAPs (the double CAPs/double sham design). Comparisons were made between the CAPs measurements and each dog's own sham responses. In another design, one dog was exposed to CAPs while the chambermate received a sham exposure; these experiments were followed by crossover of the protocol the subsequent week (the crossover design). Comparisons were made between the CAPs exposure and both the chambermate's sham and each dog's own sham responses. The crossover experiments were conducted in normal animals and in animals who had undergone balloon occlusion of the left anterior descending (LAD) coronary artery to induce myocardial compromise. The effects of CAPs in animals with induced chronic bronchitis were part of the original specific aims; because these studies were not fully pursued, the results are presented only in Appendix A. In normal dogs, analyses of all double CAPs and crossover studies revealed low frequency (LF) and high frequency (HF) powers for heart rate variability (HRV) that were significantly higher for CAPs exposure compared to sham exposure. Variation in day-to-day exposure concentrations, aerosol composition, and pathophysiologic responses were also found. The crossover design, continuous measures of aerosol mass, and biologic responses were incorporated in the development of a statistical model that allowed isolation of changes associated with CAPs from changes due to animal variations. Comparison of individual exposures with this model revealed a range from no response in any measured parameter to statistically significant changes in cardiac autonomic balance, pulmonary air flow, and breathing pattern. On days in which dogs showed statistically significant changes in responses, the findings were consistent in both cardiac and respiratory parameters. Days associated with significant increases in LF and HF HRV, LF/ HF HRV ratio, and heart rate standard deviation (HR SD) were also associated with decreases in average heart rate. These same days had decreases in respiratory frequency, tidal volume, minute volume, and peak flows with corresponding increases in respiratory cycle times and enhanced pause (Pauenh), a measure of bronchoconstriction. These cardiac and respiratory changes suggest an effect mediated via both the sympathetic nervous system and the vagus nerve. Alternatively, days associated with increased heart rate had decreases in the HR SD; decreases or no change in HF and LF HRV; increases in respiratory flows and volumes; and decreases in breathing cycle times, all suggesting only sympathetic nervous system mediation. When all data from the crossover design experiments were assessed with this model, the heart rate and respiratory rate were significantly decreased in relation to both cumulative and actual exposure and the LF HRV, LF/HF HRV ratio, HR SD, and all other respiratory parameters were significantly increased (p < 0.0001 for all). When cardiac data were grouped by days in which the air mass trajectory came from the north or northwest (versus west, south, east, or northeast), significant increases in HR SD and HF HRV and significant decreases in average heart rate were associated with the northwest trajectory. (ABSTRACT TRUNCATED)

Development and Validation of a High-Volume, Low-Cutoff Inertial Impactor.

A low-cutoff, high-volume conventional impactor has been designed. This sampler uses a slit-shaped acceleration jet and operates at 1100 L/min. The impaction substrate is polyurethane foam (PUF). The impactor collection efficiency was characterized using polydisperse particles, and the 50% size cutoff point was 0.12 ¡m. Losses within the sampler were also characterized and were less than 10%. The use of polyurethane foam (PUF) as a substrate has the following advantages: (I) PUF has a very high particle collection efficiency over a large range of particle sizes, even under conditions of heavy particle loading, as compared to other impaction substrates, such as flat plates and less porous membranes, which typically are subject to significant bounce-off and reentrainment; (2) no oil or grease coating is required, so potential interferences of impurities within such coatings are avoided when chemical, biological, and toxicological tests are performed on the collected particles; (3) PUF itself is chemically inert, minimizing interference with any of these tests; (4) because of the high flow rate of 1100 L/min, a large amount of particles can be collected in a short period of time on a relatively small surface of substrate, facilitating recovery of the collected particles for the different tests; and (5) a large amount of particles can be collected on a relatively small collection surface and easily extracted with small amounts of water or organic solvents. This method will be suitable for the collection of large amounts for toxicological studies and analysis of organic aerosols, which is not possible with other high-volume samplers that utilize large filtration surfaces.

Inhaled concentrated ambient particles are associated with hematologic and bronchoalveolar lavage changes in canines.

Pulmonary inflammatory and hematologic responses of canines were studied after exposure to concentrated ambient particles (CAPs) using the Harvard ambient particle concentrator (HAPC). For pulmonary inflammatory studies, normal dogs were exposed in pairs to either CAPs or filtered air (paired studies) for 6 hr/day on 3 consecutive days. For hematologic studies, dogs were exposed for 6 hr/day for 3 consecutive days with one receiving CAPs while the other was simultaneously exposed to filtered air; crossover of exposure took place the following week (crossover studies). Physicochemical characterization of CAPs exposure samples included measurements of particle mass, size distribution, and composition. No statistical differences in biologic responses were found when all CAPs and all sham exposures were compared. However, the variability in biologic response was considerably higher with CAPs exposure. Subsequent exploratory graphical analyses and mixed linear regression analyses suggested associations between CAPs constituents and biologic responses. Factor analysis was applied to the compositional data from paired and crossover experiments to determine elements consistently associated with each other in CAPs samples. In paired experiments, four factors were identified; in crossover studies, a total of six factors were observed. Bronchoalveolar lavage (BAL) and hematologic data were regressed on the factor scores. Increased BAL neutrophil percentage, total peripheral white blood cell (WBC) counts, circulating neutrophils, and circulating lymphocytes were associated with increases in the aluminum/silicon factor. Increased circulating neutrophils and increased BAL macrophages were associated with the vanadium/nickel factor. Increased BAL neutrophils were associated with the bromine/lead factor when only the compositional data from the third day of CAPs exposure were used. Significant decreases in red blood cell counts and hemoglobin levels were correlated with the sulfur factor. BAL or hematologic parameters were not associated with increases in total CAPs mass concentration. These data suggest that CAPs inhalation is associated with subtle alterations in pulmonary and systemic cell profiles, and specific components of CAPs may be responsible for these biologic responses.

Indoor, outdoor, and regional summer and winter concentrations of PM10, PM2.5, SO4(2)-, H+, NH4+, NO3-, NH3, and nitrous acid in homes with and without kerosene space heaters.

Twenty-four-hour samples of PM10 (mass of particles with aerodynamic diameter < or = 10 microm), PM2.5, (mass of particles with aerodynamic diameter < or = 2.5 microm), particle strong acidity (H+), sulfate (SO42-), nitrate (NO3-), ammonia (NH3), nitrous acid (HONO), and sulfur dioxide were collected inside and outside of 281 homes during winter and summer periods. Measurements were also conducted during summer periods at a regional site. A total of 58 homes of nonsmokers were sampled during the summer periods and 223 homes were sampled during the winter periods. Seventy-four of the homes sampled during the winter reported the use of a kerosene heater. All homes sampled in the summer were located in southwest Virginia. All but 20 homes sampled in the winter were also located in southwest Virginia; the remainder of the homes were located in Connecticut. For homes without tobacco combustion, the regional air monitoring site (Vinton, VA) appeared to provide a reasonable estimate of concentrations of PM2.5 and SO42- during summer months outside and inside homes within the region, even when a substantial number of the homes used air conditioning. Average indoor/outdoor ratios for PM2.5 and SO42- during the summer period were 1.03 +/- 0.71 and 0.74 +/- 0.53, respectively. The indoor/outdoor mean ratio for sulfate suggests that on average approximately 75% of the fine aerosol indoors during the summer is associated with outdoor sources. Kerosene heater use during the winter months, in the absence of tobacco combustion, results in substantial increases in indoor concentrations of PM2.5, SO42-, and possibly H+, as compared to homes without kerosene heaters. During their use, we estimated that kerosene heaters added, on average, approximately 40 microg/m3 of PM2.5 and 15 microg/m3 of SO42- to background residential levels of 18 and 2 microg/m3, respectively. Results from using sulfuric acid-doped Teflon (E.I. Du Pont de Nemours & Co., Wilmington, DE) filters in homes with kerosene heaters suggest that acid particle concentrations may be substantially higher than those measured because of acid neutralization by ammonia. During the summer and winter periods indoor concentrations of ammonia are an order of magnitude higher indoors than outdoors and appear to result in lower indoor acid particle concentrations. Nitrous acid levels are higher indoors than outdoors during both winter and summer and are substantially higher in homes with unvented combustion sources.

A passive ozone sampler based on a reaction with nitrite.

Standard ozone monitoring techniques utilize large, heavy, and expensive instruments that are not easily adapted for personal or microenvironmental monitoring. For large-scale monitoring projects that examine spatial variations of a pollutant and human exposure assessments, passive sampling devices can provide the methodology to meet monitoring and statistical goals. Recently, we developed a coated filter for ozone collection that we used in a commercially available passive sampling device. Successful preliminary results merited further validation tests, which are presented in this report. The passive ozone sampler used in field and laboratory experiments consists of a badge clip supporting a barrel-shaped body that contains two coated glass fiber filters. The principle component of the coating is nitrite ion, which in the presence of ozone is oxidized to nitrate ion on the filter medium (NO2- + O3 produces NO3- + O2). After sample collection, the filters were extracted with ultrapure water and analyzed for nitrate ion by ion chromatography. The results from laboratory and field validation tests indicated excellent agreement between the passive method and standard ozone monitoring techniques. We determined that relative humidity (ranging from 10% to 80%) and temperature (ranging from 0 degrees C to 40 degrees C) at typical ambient ozone levels (40 to 100 parts per billion) do not influence sampler performance. Face velocity and sampler orientation with respect to wind direction were found to affect the sampler's collection rate of ozone. Using a protective cup, which acts as both a wind screen and a rain cover, we were able to obtain a constant collection rate over a wide range of wind speeds.

Europium as a fluorescent probe of transfer RNA structure.

The binding of europium(III) to Escherichia coli tRNA-fMet,Glu and to unfractionated E. coli tRNA has been investigated by using the 4-thiouridine sensitization of europium 5-Do yields 7-F1 emission and changes in the lifetime of the 5-Do state of europium reported earlier (J. M. Wolfson and D. R. Kearns (1974), J. Am. Chem. Soc. 96, 3653). Binding of the first 3-4 europium ions is independent and sequential, approximately 600 times stronger than the magnesium binding, and the binding sites are located near the 4-thiouridine residue found at position 8 in a number of E. coli tRNA. Competition experiments suggest the strong binding sites are the same for magnesium and europium. The europium binding properties of both unfractionated E. coli tRNA and purified tRNA-fMet are quite similar, indicating that the location of the strong binding sites and their binding constants are nearly the same for a large group of tRNA. The europium binding properties of native and denatured tRNA are quite different, however.