Contribution of agricultural fire and wildfire smoke PM2.5 concentrations in rural regions of the US and the associated health impacts

Abstract

Exposure to landscape fire smoke is a growing public health concern. Fine particulate matter (PM2.5) from these fires has been associated with various adverse health outcomes, yet many rural and underserved regions lack adequate monitoring to support meaningful epidemiologic analysis. This dissertation quantifies the smoke exposure in New Mexico and southern Florida. We also conduct an epidemiological analysis with health data in New Mexico to determine the sensitivity of different inputs. In Chapter 2, we used public low-cost PurpleAir sensors, regulatory monitors, and 29 PurpleAir sensors deployed for this study to quantify PM2.5 from agricultural fires. We found satellite imagery is of limited use for detecting smoke from agricultural fires in Florida due to the cloud cover, overnight smoke, and the fires being small and short-lived. For these reasons, surface measurements are critical for capturing increases in PM2.5 from smoke, and we used multiple smoke designation methods. During the study period, median 24-hour PM2.5 concentrations increased on smoke-impacted days compared to unimpacted days, with smoke observed. We contrasted the region near the Everglades Agricultural Area (EAA) with large populations of low-income and minoritized groups to the more affluent coastal region. The inland region experienced more smoke-impacted monitor days than the Florida east coast region, and there was a higher study-average smoke PM2.5 concentration in the inland area. These findings highlight the need to increase air quality monitoring near the EAA. In Chapter 3, we use Emergency Department (ED) visits in an epidemiological analysis to better understand the uses of four smoke exposure estimates in NM during summer 2022: 1) PM2.5 from the EPA regulatory-grade monitors, 2) PM2.5 from both the US Environmental Protection Agency (EPA) regulatory-grade monitors and low-cost PurpleAir observations, 3) modeled 24-hour average wildfire smoke PM2.5 from the Community Multiscale Air Quality Modeling System (CMAQ), and 4) CMAQ daily 1-hour maximum wildfire smoke. We found significant associations with all-respiratory related ED visits, including pneumonia and heart failure. However, the magnitude and significance of associations varied across the four smoke-exposure products. We found modeled CMAQ output was less suitable for this epidemiological study, while the smoke exposure estimate that leveraged both regulatory and PurpleAir measurements provided more precise exposure estimates, highlighting the importance of low-cost sensors in rural regions. Our findings emphasize the need to critically assess the inputs used in epidemiological studies for accurate and meaningful results. In Chapter 4, we compared the use of ED visits to Syndromic Surveillance (SS) reports from 2019-2022 in New Mexico. Previous epidemiological studies used hospitalizations and Emergency Department (ED) visits to understand the impact of smoke exposure on human health. However, there is typically a substantial delay for these health datasets to be received by state health agencies. Syndromic Surveillance (SS) is a real-time, voluntary reporting system chief complaints and/or discharge diagnoses from the ED, which has been used in fewer epidemiological studies of wildfire smoke exposure. We conducted a time-stratified case crossover study to compare association between wildfire smoke exposure and ED visits versus SS from 2019-2022 in New Mexico. We found some consistency in our results for all respiratory-related, asthma, and all-cardiovascular related ED visits versus SS reports; however, there were meaningful differences in significance and magnitudes of several odds ratios in comparing the two types of outcomes. The "air quality related" SS data query may be useful for studying the impact of wildfire smoke exposure. We found significantly increased odds with this query in our study, with comparable results to all respiratory-related SS reports. Overall, we hypothesize that SS could be a valuable tool for allocating resources in New Mexico during an intense, local wildfire event. Future research work should be conducted to further our understanding of the use of SS in epidemiological studies of wildfire smoke exposure.