Thursday, December 18, 2025

Sharp Spike in ER Illness After Eaton Fire Smoke, Cedars-Sinai Study Shows

Emergency room visits surged for heart attacks, lung illness and systemic symptoms following January wildfires

Emergency room visits for heart attacks, lung illness and severe systemic symptoms rose sharply among Pasadena-area residents exposed to smoke from the Eaton Fire in Altadena and the Palisades Fire, according to a Cedars-Sinai Medical Center study that has a key clarification to its reported findings.

The study, published Dec. 16 in the Journal of the American College of Cardiology, found a 46% increase in acute myocardial infarction, a 24% increase in acute pulmonary illness, and a 218% increase in abnormal blood chemistry encounters during the 90 days after the Jan. 7 fire ignitions.

Cedars-Sinai said general illness encounters rose by about 118% over the same period, while the 218% statistic applies specifically to the increase in abnormal blood chemistry encounters, which rose at a rate ratio of 2.18, meaning the frequency more than doubled.

Although Cedars-Sinai is located roughly 20 miles from Pasadena, investigators said the health effects were directly tied to smoke from the Eaton Fire, which burned about 14,000 acres in Altadena/Pasadena foothills, and the Palisades Fire on the Westside.

Together, the fires destroyed thousands of homes and other structures, according to fire-agency data and wildfire-impact analyses cited in the investigative report.

Susan Cheng, senior author of the study, said in a Cedars-Sinai statement that wildfires burning into urban areas “are extremely dangerous because of how quickly they move and what they burn and release into the environment.” She said the Eaton and Palisades fires “had an immediate effect on people’s health.”

The study found that abnormal blood chemistry markers increased by 218%, a result Cheng described as evidence of systemic toxicity and biochemical metabolic stress. Joseph Ebinger, lead author, said the abnormalities suggest the body was responding to “an external stressor such as toxins in the air.”

The findings align with Los Angeles County Department of Public Health surveillance data showing that wildfire-associated emergency visits increased eightfold during the first six days of the fires, even as overall countywide ER visits fell 9% — a drop officials say may reflect evacuations, disruptions in normal activity, and people seeking care in other settings or counties. Researchers noted this “visit volume paradox” indicates that while fewer people sought care overall, those who did were often significantly sicker.

The Cedars-Sinai results also highlight a contrast with a separate Kaiser Permanente study, which reported a 42% increase in virtual respiratory visits and a 27 to 31% increase in virtual cardiovascular visits during the same period. Researchers said the difference reflects diverging patient behavior: Cedars-Sinai captured high-acuity in-person emergencies, while Kaiser documented a surge in remote care.

Air quality data show that PurpleAir sensors near the burn zones recorded particulate matter levels above 225 micrograms per cubic meter, while downtown Los Angeles reached 101.7 micrograms per cubic meter. The Journal of the American College of Cardiology study also documented a shift in regional PM2.5 averages, with pre-fire concentrations at 20.1 ± 14.5 µg/m³ and post-fire concentrations rising to 33.6 ± 86.2 µg/m³ during the week after fire onset.

Cedars-Sinai researchers said the systemic illness findings — including the 218% increase in abnormal blood chemistry — have not been documented in previous wildfire studies and may be linked to the “urban fuel” component of the fires, which burned structures, paint, chemicals, insulation and other synthetic materials in addition to vegetation. They said this mix may have contributed to the unusual “biochemical metabolic stress” pattern observed in patients.

The study population remained stable across comparison years, with U.S. Census estimates ranging from 1.22 million to 1.26 million between 2018 and 2024, and 1.216 million in 2025. Researchers used interrupted time series analysis, generalized least squares models, autoregressive moving average corrections, and manual chart review to validate ICD-10 diagnoses across the 39 ZIP codes in Cedars-Sinai’s catchment area.

The report recommends further investigation into the toxic mix of materials burned in the Eaton Fire and calls for localized data from hospitals closer to the burn zone. Huntington Hospital in Pasadena has not released comparable figures. The Cedars-Sinai team noted that if their facility saw major increases from 20 miles away, the impact in Pasadena and Altadena “was likely far worse.”