A multicity study of wintertime inversions and acute cardiorespiratory health events in the western U.S.

摘要 确定空气污染源对于制定缓解战略以保护人类健康至关重要。许多城市 在美国西部，短期PM2.5升高，由不同种类的PM2.5混合物组成， 随季节变化。PM2.5是主PM2.5(直接从污染源排放的气溶胶)和二次PM2.5的混合物 (大气中的气溶胶是由主要污染物、前体排放和大气反应形成的 进程)。虽然源解析模型可以应用于追踪污染物的排放源，但所有 传统的源分配模型有一个共同的局限性：只分配主PM2.5。 气象对西部较冷月份空气污染浓度升高起着重要作用。 在典型的气象条件下，气温会随着海拔的升高而降低。在倒置过程中，这 关系是相反的-温暖的空气保持在较冷的空气之上，导致环境空气污染物，如PM2.5，被困住 接近地面水平。历史上几次重大的空气污染事件，包括1952年伦敦的“大烟雾”，都是由 通过倒置。在美国西部较冷的月份，超过80%的PM2.5是次要的 PM2.5。为了在这些城市制定有效的法规来保护人类健康，空气质量管理人员必须了解 二次PM2.5的来源。鉴于二次PM2.5在较冷的月份占主导地位，现有来源 分摊模型不能可靠地确定缓解战略应优先考虑哪个来源(S)。 我们建议通过开发一个创新的空气质量模型来解决这个公共卫生问题，该模型可以分摊 一次和二次PM2.5，并在12个城市的大型流行病学研究中使用该模型的估计。 我们将开发一种新的数据融合方法，将空气质量模型结果和PM2.5观测结果相结合，以 为主要和次要的PM2.5物种创建季节性、特定位置的来源配置文件。这些新来源 将在多年源分配模型中使用轮廓来估计年内PM2.5的每日源浓度 博伊西、盐湖城、普罗沃、奥格登、丹佛、里诺、拉斯维加斯、萨克拉门托、弗雷斯诺、莫德斯托、 贝克尔斯菲尔德和维萨利亚。来自这些城市的急诊科就诊数据将被用来估计 PM2.5源浓度估计和心肺急诊之间的差异。 我们的项目直接解决了现有来源分配方法中的主要限制，通过开发 方法对二次PM2.5进行分摊。我们的多城市流行病学分析将通过以下方式为文献做出独特贡献 提供来源特定的健康协会，全面说明初级和二级PM2.5 源自特定来源的。我们关注PM2.5在美国西部易发城市的重大公共卫生问题 但我们的新的源解析方法可以很容易地应用 到其他地区和研究。我们的研究结果将直接关系到空气质量和公众健康 利益攸关方，为减少高污染天数和保护公众健康的政策制定提供信息。

ABSTRACT Identifying air pollution sources is critical for developing mitigation strategies to protect human health. Many cities in the western United States experience elevated short-term PM2.5, composed of heterogeneous PM2.5 mixtures that vary seasonally. PM2.5 is a mixture of primary PM2.5 (aerosols emitted directly from a source) and secondary PM2.5 (aerosols formed in the atmosphere from reactions involving primary pollutants, precursor emissions, and atmospheric processes). Although source apportionment models can be applied to trace pollutants back to their emission sources, all conventional source apportionment models share a common limitation: only the primary PM2.5 is apportioned. Meteorology plays a significant role in elevated air pollution concentrations during colder months in the western U.S. Under typical meteorological conditions, temperature decreases as altitude increases. During an inversion, this relationship is inverted – warm air is held above cooler air – causing ambient air pollutants, such as PM2.5, to be trapped near ground level. Several major historical air pollution events, including the 1952 London “Great Smog,” were caused by inversions. During colder months in the western U.S., it is common for over 80% of the total PM2.5 to be secondary PM2.5. To create effective regulations to protect human health in these cities, air quality managers must understand the origin of secondary PM2.5. Given the predominance of secondary PM2.5 during colder months, existing source apportionment models cannot reliably identify which source(s) should be prioritized for mitigation strategies. We propose to address this public health problem by developing an innovative air quality model that apportions both primary and secondary PM2.5, and to use the estimates from this model in a large 12-city epidemiologic study. We will develop a new data fusion method that combines air quality model results and speciated PM2.5 observations to create seasonal, location-specific source profiles for both primary and secondary PM2.5 species. These new source profiles will be used in a multi-year source apportionment model to estimate daily PM2.5 source concentrations during colder months for Boise, Salt Lake City, Provo, Ogden, Denver, Reno, Las Vegas, Sacramento, Fresno, Modesto, Bakersfield, and Visalia. Emergency department visit data from these cities will be used to estimate associations between the PM2.5 source concentration estimates and cardiorespiratory emergency visits. Our project directly addresses major limitations in existing source apportionment approaches by developing methods to apportion secondary PM2.5. Our multicity epidemiologic analyses will uniquely contribute to the literature by providing source-specific health associations that comprehensively account for both primary and secondary PM2.5 originating from a given source. We focus on the significant public health problem of PM2.5 in western U.S. cities prone to inversions and accompanying PM2.5 spikes, but our novel source apportionment methodologies can be readily applied to other regions and studies. Findings from our study will be of immediate interest to air quality and public health stakeholders, informing policy development to reduce high pollution days and protect public health.