This study examines the spatial distribution and temporal trend of PM2.5 constituent concentrations in California over two decades and evaluates spatial disparity of sub-population exposures, as well as the influence of interregional air pollution transport and other source contributions for PM2.5 constituent concentrations. The project builds machine learning models using existing ground measurement data, extensive satellite data, meteorological data, and other spatiotemporal data sources. The results will provide insight into PM2.5 mitigation strategies that takes into account social equity.
Framework: Early evidence showed overall reduction in outdoor air pollution levels across the globe due to COVID-19-related lockdown. However, a comprehensive assessment was needed to examine indoor air quality during the period of stay-at-home orders, given that residential indoor environment contributes most to personal exposures. We examined temporal and diurnal variations of indoor PM2.5 based on real-time measurements from indoor-outdoor co-located low-cost PurpleAir sensor sets across California for pre-, during and post-lockdown periods in 2020 and "business-as-usual" periods in 2019.
Results: Results of the research showed that the contribution of indoor-generated PM2.5 to total indoor concentrations increased as high as 80% during and post-lockdown periods compared to before lockdown.
Conclusions: This study indicated strong public health implications as it highlights the increase in residential indoor air pollution levels due to more indoor emissions as more people are expected to work/study from home in the future compared to the pre-COVID time.
Framework: Fireworks are often used in celebration, causing short term, extremely high particulate matter air pollution. We used real-time PM2.5 measurements from 751 PurpleAir sensors operating from June to July in 2019 and 2020 to examine the impact of 4th of July fireworks on hourly and daily PM2.5 concentrations at the Census tract and county levels in California. American Community Survey (ACS) and CalEnviroScreen3.0 data were also used to identify correlations between PM2.5 and socioeconomic status (SES).
Results: Relative to 2019, peak PM2.5 concentrations on July 4th and 5th of 2020 were over 50% higher in California, on average, likely due to the COVID-19-related increase in the use of household-level fireworks. Spatial hot spot analyses generally showed these southern counties (which tended to have less strict firework-related regulations and greater use of illegal fireworks) as regional air pollution hotspots, whereas the opposite pattern was seen in the north (e.g. San Francisco). Results also showed over two-times higher PM2.5 peaks among communities with lower SES, higher minority group populations, and higher asthma rates.
Conclusions: Our findings highlight the important role that policy and enforcement can play in reducing firework-related air pollution and protecting public health, as exemplified by southern California where policy was more relax and air pollution was higher (especially in 2020 when the 4th of July coincided with the COVID-19-lockdown period), and in disadvantaged communities where disparities were greatest.
Framework: Recent warehouse developments in Southern California, especially Empire inland region has changed the transportation characteristics of the nearby neighborhoods, with a massive increase in the truck traffic transporting goods from ports of Los Angeles and Long Beach to the inner land. PurpleAir sensor network data in Los Angeles County will help us to identify hotspots of PM2.5 that could potentially be related to the warehouse development. In this project, with the help of faculty members from school of business at UCI, we will quantify the environmental and financial benefits of potential solutions to this problem.
Framework: One of the growing public health threats in the recent years is exposure to harmful wildfire smoke. In this project, we are using the recently developed indoor-outdoor low-cost air pollution sensor network known as PurpleAir to quantify the changes in indoor/outdoor air pollution levels during the wildfires in surrounding communities. We will examine the effectiveness of cautionary actions to reduce indoor infiltrations on indoor PM2.5 levels. Additionally, we are investigating the relationship between such impacts and various socioeconomic factors at the Census tract level to identify the most important factors.
