Department of Environmental & Occupational Health Sciences, School of Public Health, University of Washington, Seattle, WA, USA.
United States Environmental Protection Agency (Retired), Santa Rosa, CA, USA.
Environ Pollut. 2021 May 1;276:116763. doi: 10.1016/j.envpol.2021.116763. Epub 2021 Feb 16.
Epidemiological research on the adverse health outcomes due to PM exposure frequently relies on measurements from regulatory air quality monitors to provide ambient exposure estimates, whereas personal PM exposure may deviate from ambient concentrations due to outdoor infiltration and contributions from indoor sources. Research in quantifying infiltration factors (F), the fraction of outdoor PM that infiltrates indoors, has been historically limited in space and time due to the high costs of monitor deployment and maintenance. Recently, the growth of openly accessible, citizen-based PM measurements provides an unprecedented opportunity to characterize F at large spatiotemporal scales. In this analysis, 91 consumer-grade PurpleAir indoor/outdoor monitor pairs were identified in California (41 residential houses and 50 public/commercial buildings) during a 20-month period with around 650000 h of paired PM measurements. An empirical method was developed based on local polynomial regression to estimate site-specific F. The estimated site-specific F had a mean of 0.26 (25, 75 percentiles: [0.15, 0.34]) with a mean bootstrap standard deviation of 0.04. The F estimates were toward the lower end of those reported previously. A threshold of ambient PM concentration, approximately 30 μg/m, below which indoor sources contributed substantially to personal exposures, was also identified. The quantified relationship between indoor source contributions and ambient PM concentrations could serve as a metric of exposure errors when using outdoor monitors as an exposure proxy (without considering indoor-generated PM), which may be of interest to epidemiological research. The proposed method can be generalized to larger geographical areas to better quantify PM outdoor infiltration and personal exposure.
PM 暴露导致不良健康后果的流行病学研究通常依赖于监管空气质量监测器提供的环境暴露估计值，而个人 PM 暴露可能因室外渗透和室内源的贡献而偏离环境浓度。由于监测器部署和维护成本高昂，量化渗透因子 (F)（渗透到室内的室外 PM 分数）的研究在空间和时间上一直受到限制。最近，公开获取的、基于公民的 PM 测量的增长为在大时空尺度上表征 F 提供了前所未有的机会。在这项分析中，在 20 个月的时间内，在加利福尼亚州确定了 91 对消费者级别的 PurpleAir 室内/室外监测器对（41 个住宅和 50 个公共/商业建筑），进行了约 650000 小时的 PM 配对测量。基于局部多项式回归，开发了一种经验方法来估计特定地点的 F。估计的特定地点 F 的平均值为 0.26（25%，75%百分位数：[0.15, 0.34]），平均引导标准偏差为 0.04。F 估计值处于先前报道的较低水平。还确定了一个环境 PM 浓度阈值，约为 30μg/m，低于该阈值，室内源对个人暴露的贡献很大。室内源贡献与环境 PM 浓度之间的量化关系可作为使用室外监测器作为暴露替代物（不考虑室内生成的 PM）时暴露误差的度量，这可能对流行病学研究感兴趣。该方法可以推广到更大的地理区域，以更好地量化 PM 室外渗透和个人暴露。
