Built Environment & Energy Laboratory
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Chen, C., Zhao, B., Weschler, C.J. (2012). Indoor exposure to outdoor PM10: assessing its influence on the relationship between PM10 and short-term mortality in U.S. cities. Epidemiology, 23, 870-878. (Particle penetration, Particulate matter, Building)

Background: Seasonal and regional differences have been reported for the increase in short-term mortality associated with a given increase in the concentration of outdoor particulate matter with an aerodynamic diameter smaller than 10 μm (PM10 mortality coefficient). Some of this difference may be because of seasonal and regional differences in indoor exposure to PM10 of outdoor origin. Methods: From a previous study, we obtained PM10 mortality coefficients for each season in seven U.S. regions. We then estimated the change in the sum of indoor and outdoor PM10 exposure per unit change in outdoor PM10 exposure (PM10 exposure coefficient) for each season in each region. This was originally accomplished by estimating PM10 exposure coefficients for 19 cities within the regions for which we had modeled building infiltration rates. We subsequently expanded the analysis to include 64 additional cities with less well-characterized building infiltration rates. Results: The correlation (r = 0.71 [95% confidence interval = 0.46 to 0.86]) between PM10 mortality coefficients and PM10 exposure coefficients (28 data pairs; four seasons in each of seven regions) was strong using exposure coefficients derived from the originally targeted 19 National Morbidity, Mortality, and Air Pollutions Study cities within the regions. The correlation remained strong (r = 0.67 [0.40 to 0.84]) when PM10 exposure coefficients were derived using 83 cities within the regions (the original 19 plus the additional 64). Conclusions: Seasonal and regional differences in PM10 mortality coefficients appear to partially reflect seasonal and regional differences in total PM10 exposure per unit change in outdoor exposure.  

Chen, C., Zhao, B., Weschler, C.J. (2012). Assessing the influence of indoor exposure to "outdoor ozone" on the relationship between ozone and short-term mortality in US communities. Environmental Health Perspectives, 120, 235-240. (Ozone penetration, Ozone, Building)

Background: City-to-city differences have been reported for the increase in short-term mortality associated with a given increase in ozone concentration (ozone mortality coefficient). Although ozone concentrations are monitored at central outdoor locations, a large fraction of total ozone exposure occurs indoors. Objectives: To clarify the influence of indoor exposure to ozone of outdoor origin on short-term mortality, we conducted an analysis to determine whether variation in ozone mortality coefficients among U.S. cities might be partly explained by differences in total ozone exposure (from both outdoor and indoor exposures) resulting from the same outdoor ozone concentration. Methods: We estimated average annual air change rates (the overall rate at which indoor air is replaced with outdoor air) and used these to estimate the change in total ozone exposure per unit change in outdoor ozone exposure (ozone exposure coefficient) for 18 cities that had been included in the National Morbidity and Mortality Air Pollution Study (NMMAPS). We then examined associations between both parameters and published ozone mortality coefficients. Results: For the 18 targeted NMMAPS cities, the association between ozone mortality coefficients and ozone exposure coefficients was strong (1-hr ozone metric: R2 = 0.58, p < 0.001; 8-hr ozone: R2 = 0.56, p < 0.001; 24-hr ozone: R2 = 0.48, p = 0.001). When extended to another 72 NMMAPS cities, the associations remained strong (R2 = 0.47–0.63; p < 0.001). Conclusions: Differences in ozone mortality coefficients among cities appear to partially reflect differences in total ozone exposure resulting from differences in the amount of outdoor ozone that is transported indoors.

Chen, C., Zhao, B., Zhou, W., Jiang, X., Tan, Z. (2012). A methodology for predicting particle penetration factor through cracks of windows and doors for actual engineering application. Building and Environment, 47, 339-348. (Particle penetration, Particulate matter, Building)

Epidemiologic evidences have shown a strong relationship between exposure to outdoor particles and adverse impact on human health. A large amount of outdoor particles may penetrate into the indoor environments, where people spend about 90% of their life time. Therefore, predicting particle penetration into buildings could help to quantify the indoor exposure to particles with an outdoor origin and thus to develop effective strategies to remediate the exposure. However, there are few methodologies of particle penetration prediction for actual engineering application. In this paper, we present a methodology for predicting the particle penetration factor for real buildings by estimating the geometries of the cracks in the building envelopes according to the American Society of Heating, Refrigeration, Air-Conditioning Engineers (ASHRAE) Handbook. In addition, the effect of inertial impaction was considered. Furthermore, the effect of gravitational settling was neglected for vertical leakages. Two field measurements showed that the proposed methodology was effective in predicting the particle penetration factor for the test rooms. For particles in the range of 0.5 to 6 μm in diameter, the experimental data of penetration factors vary from 0.2 to 1, which match well with the predicted data. Generally speaking, this methodology can be used to aid the engineers or designers to calculate the particle penetration in actual engineering practices or designs. In addition, a sensitivity analysis was conducted to investigate the influencing factors.

2011 Particle