Applying a Two-stage Generalized Synthetic Control Approach to Quantify the Heterogeneous Health Effects of Extreme Weather Events: A 2018 Large Wildfire in California Event As a Case Study

Overview

Journal Environ Epidemiol

Publisher Wolters Kluwer

Specialty Environmental Health

Date 2025 Jan 2

PMID 39744585

Authors

Noemie Letellier

Maren Hale

Kasem U Salim

Yiqun Ma

Francois Rerolle

Lara Schwarz

Tarik Benmarhnia

Affiliations

Soon will be listed here.

Abstract

Extreme weather events, including wildfires, are becoming more intense, frequent, and expansive due to climate change, thus increasing negative health outcomes. However, such effects can vary across space, time, and population subgroups, requiring methods that can handle multiple exposed units, account for time-varying confounding, and capture heterogeneous treatment effects. In this article, we proposed an approach based on staggered generalized synthetic control methods to study heterogeneous health effects, using the 2018 California wildfire season as a case study. This study aimed to estimate the effects of the November 2018 California wildfires, one of the state's deadliest and most destructive wildfire seasons, on respiratory and circulatory health, document heterogeneity in health impacts, and investigate drivers of this heterogeneity. We applied a two-stage generalized synthetic control method to compare health outcomes in exposed (from 8 November to 5 December 2018) versus unexposed counties and used random-effects meta-regression to evaluate the effect modification of county-level socioeconomic variables on the observed health effects of the November 2018 wildfires. We observed an increase in respiratory hospitalizations for most exposed counties when compared with unexposed counties, with significant increases in Fresno, San Francisco, San Joaquin, San Mateo, and Santa Clara counties. No effect on circulatory hospitalizations was observed. County-level sociodemographic characteristics seem to not modulate the effects of wildfire smoke on respiratory hospitalizations. This novel two-stage framework can be applied in broader settings to understand spatially and temporally compounded health impacts of climate hazards. We provide codes in R for reproducibility and replication purposes.

References

Masri S, Jin Y, Wu J . Compound Risk of Air Pollution and Heat Days and the Influence of Wildfire by SES across California, 2018-2020: Implications for Environmental Justice in the Context of Climate Change. Climate (Basel). 2024; 10(10). PMC: 10919222. DOI: 10.3390/cli10100145. View

Aguilera R, Corringham T, Gershunov A, Benmarhnia T . Wildfire smoke impacts respiratory health more than fine particles from other sources: observational evidence from Southern California. Nat Commun. 2021; 12(1):1493. PMC: 7935892. DOI: 10.1038/s41467-021-21708-0. View

Nianogo R, Benmarhnia T, ONeill S . A comparison of quasi-experimental methods with data before and after an intervention: an introduction for epidemiologists and a simulation study. Int J Epidemiol. 2023; 52(5):1522-1533. PMC: 10555819. DOI: 10.1093/ije/dyad032. View

Davies I, Haugo R, Robertson J, Levin P . The unequal vulnerability of communities of color to wildfire. PLoS One. 2018; 13(11):e0205825. PMC: 6214520. DOI: 10.1371/journal.pone.0205825. View

Alari A, Letellier N, Benmarhnia T . Effect of different heat wave timing on cardiovascular and respiratory mortality in France. Sci Total Environ. 2023; 892:164543. DOI: 10.1016/j.scitotenv.2023.164543. View

Leibel S, Nguyen M, Brick W, Parker J, Ilango S, Aguilera R . Increase in Pediatric Respiratory Visits Associated with Santa Ana Wind-Driven Wildfire Smoke and PM Levels in San Diego County. Ann Am Thorac Soc. 2019; 17(3):313-320. DOI: 10.1513/AnnalsATS.201902-150OC. View

Liu J, Wilson A, Mickley L, Dominici F, Ebisu K, Wang Y . Wildfire-specific Fine Particulate Matter and Risk of Hospital Admissions in Urban and Rural Counties. Epidemiology. 2016; 28(1):77-85. PMC: 5130603. DOI: 10.1097/EDE.0000000000000556. View

Thilakaratne R, Hoshiko S, Rosenberg A, Hayashi T, Buckman J, Rappold A . Wildfires and the Changing Landscape of Air Pollution-related Health Burden in California. Am J Respir Crit Care Med. 2022; 207(7):887-898. DOI: 10.1164/rccm.202207-1324OC. View

Liu J, Wilson A, Mickley L, Ebisu K, Sulprizio M, Wang Y . Who Among the Elderly Is Most Vulnerable to Exposure to and Health Risks of Fine Particulate Matter From Wildfire Smoke?. Am J Epidemiol. 2017; 186(6):730-735. PMC: 5860049. DOI: 10.1093/aje/kwx141. View

10.

Sera F, Gasparrini A . Extended two-stage designs for environmental research. Environ Health. 2022; 21(1):41. PMC: 9017054. DOI: 10.1186/s12940-022-00853-z. View

11.

Rappold A, Cascio W, Kilaru V, Stone S, Neas L, Devlin R . Cardio-respiratory outcomes associated with exposure to wildfire smoke are modified by measures of community health. Environ Health. 2012; 11:71. PMC: 3506568. DOI: 10.1186/1476-069X-11-71. View

12.

Ignotti E, Valente J, Longo K, Freitas S, Hacon S, Netto P . Impact on human health of particulate matter emitted from burnings in the Brazilian Amazon region. Rev Saude Publica. 2010; 44(1):121-30. DOI: 10.1590/s0034-89102010000100013. View

13.

Sudore R, Mehta K, Simonsick E, Harris T, Newman A, Satterfield S . Limited literacy in older people and disparities in health and healthcare access. J Am Geriatr Soc. 2006; 54(5):770-6. DOI: 10.1111/j.1532-5415.2006.00691.x. View

14.

Aguilera R, Corringham T, Gershunov A, Leibel S, Benmarhnia T . Fine Particles in Wildfire Smoke and Pediatric Respiratory Health in California. Pediatrics. 2021; 147(4). DOI: 10.1542/peds.2020-027128. View

15.

Hutchinson J, Vargo J, Milet M, French N, Billmire M, Johnson J . The San Diego 2007 wildfires and Medi-Cal emergency department presentations, inpatient hospitalizations, and outpatient visits: An observational study of smoke exposure periods and a bidirectional case-crossover analysis. PLoS Med. 2018; 15(7):e1002601. PMC: 6038982. DOI: 10.1371/journal.pmed.1002601. View

16.

Childs M, Li J, Wen J, Heft-Neal S, Driscoll A, Wang S . Daily Local-Level Estimates of Ambient Wildfire Smoke PM for the Contiguous US. Environ Sci Technol. 2022; 56(19):13607-13621. DOI: 10.1021/acs.est.2c02934. View

17.

Cascio W . Wildland fire smoke and human health. Sci Total Environ. 2017; 624:586-595. PMC: 6697173. DOI: 10.1016/j.scitotenv.2017.12.086. View

18.

Reid C, Considine E, Watson G, Telesca D, Pfister G, Jerrett M . Effect modification of the association between fine particulate air pollution during a wildfire event and respiratory health by area-level measures of socio-economic status, race/ethnicity, and smoking prevalence. Environ Res Health. 2024; 1(2). PMC: 10852067. DOI: 10.1088/2752-5309/acc4e1. View

19.

Reid C, Brauer M, Johnston F, Jerrett M, Balmes J, Elliott C . Critical Review of Health Impacts of Wildfire Smoke Exposure. Environ Health Perspect. 2016; 124(9):1334-43. PMC: 5010409. DOI: 10.1289/ehp.1409277. View

20.

Zhao R, Gao Q, Hao Q, Wang S, Zhang Y, Li H . The exposure-response association between humidex and bacillary dysentery: A two-stage time series analysis of 316 cities in mainland China. Sci Total Environ. 2021; 797:148840. DOI: 10.1016/j.scitotenv.2021.148840. View