How Did The Los Angeles Wildfires Affect Acute Pulmonary and Cardiac Emergencies?

Ebinger et al. (2025) investigated how the January 2025 Los Angeles wildfires affected local residents’ health. They asked whether emergency department encounters for specific illnesses increased during and after the fires. The study analyzed Cedars-Sinai emergency encounter data from 39 affected or adjacent zip codes, comparing the 90 days post-fire with the same calendar periods in 2018–2024 using interrupted time series models. They found significant excesses in acute pulmonary illness (24% increase; RR 1.24), acute myocardial infarction (46% increase; RR 1.46), and systemic illness reflected in blood chemistry abnormalities (218% increase; RR 2.18), despite no rise in total encounters. 

Why This Article Was Selected for The Policy Scientist

Ebinger et al. (2025) address a policy issue of broad significance: the population health consequences of large-scale wildland–urban interface fires. As wildfire frequency, duration, and proximity to dense urban areas increase, understanding acute medical impacts becomes central to emergency preparedness, hospital surge planning, air quality regulation, and climate adaptation policy. This study is timely given the growing overlap between environmental shocks and health system strain. The authors have contributed extensively to cardiovascular and environmental health research, lending continuity to this line of inquiry. Using a large, real-world clinical dataset from Cedars-Sinai, they document sizable post-fire increases in pulmonary illness, myocardial infarction, and systemic abnormalities. The dataset is high-quality for utilization outcomes, though single-system scope may limit external validity. Interrupted time series methods are appropriate and statistically rigorous; future work using designs with stronger causal identification could further strengthen inference. 

Full Citation and Link to Article

Ebinger, J. E., Huang, T. Y., Joung, S. Y., Kwong, J. L. F., Warsi, W., Sun, N., Navarrette, J., Botting, P., Tan, Z. S., Claggett, B. L., Kwan, A. C., & Cheng, S. (2025). Emergency encounters for illness during and after the Los Angeles wildfires. Journal of the American College of Cardiology. Advance online publication. https://doi.org/10.1016/j.jacc.2025.10.079 

Central Research Question

Ebinger et al. (2025) examine whether the January 2025 Los Angeles wildfires were associated with measurable changes in acute health events requiring emergency medical care. The study focuses on encounters among residents living within or adjacent to wildfire-affected zip codes and asks a clinically grounded question: did the incidence of specific categories of illness—particularly pulmonary, cardiovascular, and systemic conditions—rise during the 90 days following wildfire onset compared with equivalent calendar periods in prior years? The authors are motivated by the increasing prevalence of wildland–urban interface (WUI) fires, which generate complex exposure mixtures distinct from wildland-only or urban-only fires. The research question therefore integrates environmental exposure concerns with health system utilization outcomes, emphasizing detection of excess morbidity rather than overall encounter volume.

Previous Literature

Prior work has established that wildfire smoke exposure, especially elevated concentrations of fine particulate matter (PM2.5), is associated with adverse cardiopulmonary outcomes, including exacerbations of asthma, chronic obstructive pulmonary disease, and cardiovascular events. Epidemiologic studies have documented increased hospitalizations and mortality following major wildfire episodes, with some evidence of both immediate and medium-term effects. Several cited studies report excess all-cause deaths or cardiopulmonary admissions linked to smoke exposure, often relying on regional air quality data and administrative claims. However, the literature has emphasized wildland fires more than WUI events, despite WUI smoke containing a broader array of combustion products from mixed biomass and industrial materials. In addition, relatively few studies have characterized systemic or non-organ-specific abnormalities detectable through laboratory diagnostics. Ebinger et al. position their analysis as extending beyond mortality and hospitalization metrics toward emergency department (ED) encounters and diagnostic patterns, while also probing the underexplored domain of systemic illness following WUI exposures.

Data

The study analyzes emergency encounter data from Cedars-Sinai Medical Center, the largest adult acute care hospital in Los Angeles County. The analytic sample includes encounters involving residents from 39 zip codes either directly affected by a January 2025 wildfire or geographically adjacent to an affected area. The observation window spans 2018 through early 2025, enabling comparison between the 90-day post-fire period (January 7 to April 7, 2025) and analogous calendar intervals in 2018–2024. Population stability is assessed using U.S. Census estimates, which indicate minimal variation across years, supporting comparability of encounter rates. Diagnostic outcomes are defined using International Classification of Diseases, Tenth Revision (ICD-10) discharge codes. Respiratory diagnoses are categorized into upper and lower respiratory illness, while cardiovascular outcomes include acute myocardial infarction (AMI). A distinctive feature of the dataset is the inclusion of encounters coded primarily as blood chemistry laboratory abnormalities. To enhance diagnostic validity, the authors conduct manual chart reviews on randomly selected encounters across years. Environmental context is provided by reported shifts in mean outdoor PM2.5 concentrations, which increased markedly following fire onset, albeit with high variance.

Methods

The authors employ an interrupted time series (ITS) framework using generalized least squares models with autoregressive moving average (ARMA) corrections. This approach accounts for serial correlation and temporal dependencies inherent in longitudinal utilization data. Encounter counts for each diagnostic category are regressed on an indicator representing post-fire versus pre-fire status, adjusting for secular time trends, seasonality (modeled through week and month controls), and pandemic-related disruptions (COVID-19 years 2020 and 2021). The prespecified 90-day post-fire horizon reflects prior evidence suggesting that cardiopulmonary consequences of smoke exposure may persist beyond the immediate disaster period. Rate ratios (RRs) are derived to quantify proportional changes relative to baseline trends. Statistical significance is evaluated using two-tailed tests with a threshold of P < 0.05. The modeling strategy is well suited to evaluating population-level shocks where randomized assignment is infeasible. By incorporating ARMA corrections, the authors strengthen estimation reliability and mitigate bias from autocorrelation.

Findings/Size Effects

Total ED encounters during the post-fire period do not increase significantly (post-fire RR 0.98), suggesting that the observed effects are diagnosis-specific rather than reflecting generalized utilization growth. In contrast, several clinically salient categories display statistically significant excesses. Encounters for acute pulmonary illness rise by 24% (RR 1.24; 95% CI 1.002–1.48; P = 0.041), indicating a modest but meaningful elevation consistent with prior smoke exposure literature. Acute myocardial infarction encounters increase by 46% (RR 1.46; 95% CI 1.17–1.75; P = 0.001), a comparatively large effect size that underscores potential cardiovascular vulnerability following WUI fire exposure. The most pronounced change occurs in encounters coded as blood chemistry laboratory abnormalities, which surge by 218% (RR 2.18; 95% CI 1.83–2.54; P < 0.001). Importantly, this laboratory-based excess is not paralleled by increases in readily attributable conditions such as dehydration or kidney disease, suggesting that the abnormalities may reflect broader systemic disturbances rather than coding artifacts tied to common sequelae. Co-occurring diagnoses among these encounters include heterogeneous symptoms and conditions—chest pain, syncope, dyspnea, dysrhythmia, hypertensive disorders, head injury, and sepsis—indicating clinical diversity rather than concentration in a single disease pathway.

The authors interpret the laboratory findings as evidence of systemic illness potentially linked to the chemical complexity of WUI smoke. Unlike wildland-only fires, WUI combustion involves synthetic materials and metals, generating exposures that may influence immune, inflammatory, or metabolic processes. The temporal pattern aligns with prior mortality analyses showing early spikes followed by reversion toward baseline, although the present study highlights persistence or delayed presentation for less severe conditions. Sensitivity considerations include the inability to track evacuation-related population shifts. The authors note that explaining the AMI excess through demographic change alone would require an implausibly large post-fire increase in the at-risk population.

Conclusion

Ebinger et al. (2025) conclude that the January 2025 Los Angeles WUI fires were associated with substantial, diagnosis-specific increases in emergency encounters for pulmonary illness, acute myocardial infarction, and systemic abnormalities. The absence of a rise in total encounters strengthens the inference that the wildfire event altered the composition rather than the volume of ED utilization. The study contributes to the literature by documenting cardiovascular and systemic effects alongside respiratory outcomes, thereby expanding the clinical spectrum typically associated with wildfire exposure. The findings reinforce the relevance of wildfire events as acute population health stressors with implications for hospital preparedness, surveillance systems, and environmental health policy. Limitations include reliance on zip-code-based exposure classification, lack of individual-level mitigation data, and single-center scope, which may constrain generalizability. Nevertheless, the methodological rigor of the interrupted time series design and the magnitude of observed rate ratios provide compelling evidence that WUI wildfire exposures correspond with measurable increases in severe and systemic illness requiring emergency care.