Reference: Environ Res Health. 2025 Mar 1;3(1):015002
Practice Point: Air conditioners in homes may protect against the respiratory effects of wildfire smoke exposure, even for those far from the flames.
EBM Pearl: When controlled trials are not possible, it is sometimes okay to take what is practically measurable with observational studies and extrapolate for real-life applicability.
When the skies over Southern California turned an eerie shade of orange and black, news reports tended to focus on the immediate loss of life and property, but the smoke from these fires is a growing threat to survivors, rescuers, and anyone who happens to be breathing the polluted air. Wildfire smoke releases harmful air pollutants that travel long distances, affecting even people far from the wildfires themselves. Exposure to the high concentrations of particulate matter in the air from wildfires has been linked to a range of health issues, particularly respiratory conditions such as asthma, COPD, and bronchitis.
A recent observational study evaluated claims data for more than 50 million statewide emergency department visits in California during wildfire season (typically May-November) from 2012 to 2019 and attempted to quantify the health impacts of exposure to wildfire smoke. Overall, respiratory illnesses were the most common immediate consequence of exposure to wildfire smoke, with the highest risk in Black and Hispanic populations. Notably, not having an air conditioning unit in the home was associated with a 23% relative increase in the incidence of respiratory illness on a population level. Coastal residents were the least likely to own air conditioners and the most likely to be treated for respiratory disease.
It’s important to consider here that although it was the prevalence of air conditioners that was measured, it is reasonably safe to assume that using the air conditioner, not just having one, was a likely driver in the inverse association with respiratory disease. However, access to stable housing, let alone housing with an air conditioning unit is an important consideration as well. This disparity may explain, in part, the increased risk of respiratory disease that was observed in Black and Hispanic populations. The findings of this study serve as a stark reminder that wildfire smoke isn't just a problem for people who can see the flames—it makes its way into the lungs of people near and far, with a particular toll on some of our more marginalized populations.
While California's wildfires may be a seasonal norm, the increased risk of respiratory and all-cause health issues is no small matter. This study also didn’t address the cascade of other long-term problems (social, psychological, and physical) likely triggered by wildfires. For example, data suggests that more than twice as many survivors and responders have died as a result of exposure to smoke and other inhalants from the World Trade Center attacks of 2001 than died in the original tragedy.
It seems that in the battle between human lungs and smoke-filled skies, access to air conditioners may be a form of respiratory armor. As climate change continues to fan the flames of the wildfire season, enhancing smoke exposure awareness and protecting vulnerable populations has never been more urgent.
For more information, see the topic Toxic Inhalational Injury in DynaMed.
DynaMed EBM Focus Editorial Team
This EBM Focus was written by Rich Lamkin, MPH, MPAS, PA-C, Clinical Writer at DynaMed. Edited by Alan Ehrlich, MD, FAAFP, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School; Katharine DeGeorge, MD, MS, Senior Deputy Editor at DynaMed and Associate Professor of Family Medicine at the University of Virginia; Dan Randall, MD, MPH, FACP, Senior Deputy Editor at DynaMed; McKenzie Ferguson, PharmD, BCPS, Senior Clinical Writer at DynaMed; Matthew Lavoie, Senior Medical Copyeditor, BA, at DynaMed; Hannah Ekeh, MA, Senior Associate Editor II at DynaMed; and Jennifer Wallace, BA, Senior Associate Editor at DynaMed.