Wildfire smoke was associated with an increase in healthcare utilization, particularly among vulnerable pediatric populations, according to research published in the Annals of the American Thoracic Society.
Investigators set out to quantify healthcare utilization in San Diego County, California following the Lilac Fire, which took place in December 2017, among pediatric patients at Rady Children’s Hospital emergency and urgent care clinics.
Data from the hospital’s EPIC electronic medical record system and PM2.5 data from the United States Environmental Protection Agency between 2011 and 2017 were used to employ an interrupted time series approach where investigators compared observed pediatric visits during the fire with the visits that would have occurred if the Lilac Fire had not taken place.
For this study, respiratory visits were defined as one of the following chief complaints: difficulty breathing, respiratory distress, wheezing, asthma, or cough.
In total, data from 154,983 emergency department and urgent care visits were analyzed. Mean patient age was 6.1 years, 69% of patients had Medi-Cal insurance, and 25% had private insurance. The median respiratory visit rate per 10,000 children per ZIP code for children aged 19 years and younger during the course of the fire event was 10.5±50.2 visits, with a highest rate of age-adjusted respiratory visits of 297 per 10,000 children in the study population.
During the Lilac Fire, the mean average daily number of respiratory-related visits was 75.1±18.6 vs 55±6.1 in the week prior to the fire. In terms of healthcare utilization trends, visits during a 7-year period (2011-2017) increased overall, with seasonal peaks during the winter and troughs during the summer.
Data analysis included all 181 ZIP codes specific to San Diego County. The investigators found that the top 5 ZIP codes with the highest standard deviations in age-adjusted respiratory visits were downwind of the fire; 3 of these ZIP codes were located within a 10-mile radius of the fire perimeter.
The Lilac Fire was also responsible for 16.03 daily respiratory emergency department visits (95% CI, 11.2-20.9), with varying effects on different subgroups. Patients aged 6 to 12 years experienced the greatest change in the number of visits associated with the Lilac Fire, with 3.4 additional daily excess respiratory emergency department visits (95% CI, 2.3-4.6); children aged 0 to 5 years had the highest absolute daily excess emergency department visits at 7.3 (95% CI, 3.0-11.7). No increases in respiratory visits were noted during the same period in 2016, when no wildfires had occurred.
Across all ZIP codes, the investigators found an average daily increase of 5.6 µg/m³ (95% CI, 3.9-7.4) in PM2.5, attributable to smoke from the fire. No increase in PM2.5 was noted during the same period in the previous years.
Study limitations included the evaluation of only one episode of wildfire despite larger fires occurring in 2003 and 2007, and the lack of evaluation of potential confounders, including weather. The researchers also noted the potential for an increased signal resulting from an “anomalously active viral respiratory season in 2017” compared with prior years.
“As the population increases and pushes the boundaries of the wildland-urban interface, ignition sources will increase, and a growing population will be exposed to smoke blown towards the densely populated coast,” the researchers concluded. “Future wildfires will increasingly affect a larger susceptible pediatric population and will require greater preparedness and evidence-based mitigation efforts.”
Leibel S, Nguyen M, Brick W, et al. Increase in pediatric respiratory visits associated with Santa Ana wind-driven wildfire smoke and PM2.5 levels in San Diego County [published online December 20, 2019]. Ann Am Thorac Soc. doi:10.1513/AnnalsATS.201902-150OC