This summer, record-breaking temperatures have been recorded throughout Europe and continue to rise globally. At this very moment, a blistering heat wave is ripping through California. These extremes have led to heat-related injuries, regional fires, severe weather events, and increased morbidity, especially for those with chronic respiratory illnesses. Unfortunately, the extraordinary is becoming ordinary as the average ambient temperature has risen since 1980, reaching its highest level in 2016 and 2020 (see figure 1).
Healthcare professionals must meet this evolving challenge with increased awareness, strategies, and advocacy to successfully navigate patient populations exposed to extreme heat, decreased air quality, and wildfire smoke. Here we will discuss the basic risks of excess heat, the impact of extreme heat and poor air quality on respiratory health, challenges posed by wildfire smoke, and resources for healthcare professionals to advise those with chronic respiratory diseases.
The Risks of Excess Heat
The U.S. Global Changes Research Program documents the health impact of severe heat events as described in CDC Morbidity and Mortality Weekly reports, recording deaths related to severe heat waves in Kansas City and St. Louis (1980), Chicago (1995), and California (2006). These relationships were further explored through extensive cohort studies in Europe and the U.S., which showed that hospital admissions for respiratory symptoms and deaths were correlated with heat events. Michelozzi et al., postulated that patients with chronic respiratory diseases might have impaired thermoregulatory systems and may hyperventilate, creating more dynamic hyperinflation or pulmonary vasoconstriction.
However, this population isn’t the only group susceptible to direct heat-related illness, especially as temperatures continue to rise.
Heat-related illnesses can result when normal mechanisms of thermoregulation are overwhelmed. The illness is particularly witnessed as the ambient temperature rises above normal body temperature and humidity limits the ability to dissipate heat via evaporation. The most dangerous form is heatstroke, in which hyperthermia (core temperature > 105°F) is combined with altered mental status, seizures, and coma. Heat stroke is accelerated by hypovolemia from fluid loss to the environment, which results in cutaneous vasoconstriction and an inability to shift heat from the core to the surface for dissipation. Heat exhaustion is less severe but needs prompt attention as it can progress to heatstroke. The hallmark of the transition from heat exhaustion to heat stroke is a change in mental status. Treatment should not be delayed and includes removal of insulating clothing, cold water immersion, ice packs, and replacement of intravascular volume and electrolytes.
Importantly, as a first line defense mechanism, prevention and awareness of the risks are key to avoiding this set of heat injuries. A CDC pamphlet on preventing heat-related illness in patients offers an important resource. It advocates common-sense measures, such as minimizing outdoor time and staying hydrated, and offers advice for high-risk groups, like those with chronic diseases.
The Impact on Air Quality and Particulate Matter
Beyond temperature, we must also consider a critical related matter: air quality. Air quality contributes to the disease burden and significantly deteriorates in extreme heat. The CDC monitors six air pollutants for air quality, including ozone and particulate matter (PM), which contribute to the Air Quality Index (AQI). Fine PM is defined by the particle sizes of PM2.5 and PM10 measured in micrograms per cubic meter.
Patients who hyperventilate — for example, those with emphysematous COPD, who require a higher minute ventilation — expose themselves to a more significant amount of PM. A New England Journal of Medicine landmark study in 2017 used the Medicare database of over 60 million patients to correlate mortality with local ozone and PM2.5 levels across the continental U.S. The results showed a strong direct correlation between ozone and PM2.5 levels with overall mortality.
Severe heatwaves are usually associated with high-pressure systems that stagnate over geographical regions. A meteorological system known as “heat dome” develops and traps air pollutants such as ozone, PM2.5, and nitrogen dioxide (NO2), decreasing air quality (see figure 2). Ozone and PM2.5 accumulate to very high levels, and when inhaled, airway inflammation, bronchoconstriction, and mucous production are initiated. Even short-term exposures to ozone and PM2.5 have been shown to increase asthma-related emergency room visits and hospitalizations. Comparably, in a panel study of asthmatics, hourly PM2.5 and temperature were evaluated for an association of lung function in adult asthmatics. The study concluded that short-term increases in PM2.5 were associated with increased rescue bronchodilator usage.
Outdoor air quality and temperature are important, but many with chronic respiratory diseases spend most of their time indoors. McCormack et al. conducted a study and found that indoor heat was associated with worsening scores for breathlessness, cough, and sputum production. Elevated levels of NO2 and PM2.5 magnified the effect. And energy-efficient homes can trap and concentrate ozone, NO2, PM, smoke, and dander.
The Role of Wildfire Smoke
The past decade has seen a tremendous increase in wildfires across the globe. Wildfire season in the U.S. is longer, with more severe fires and consumed acreage. Wildfires generate the same chemical pollutants previously discussed, but in larger concentrations. Several studies have shown increased bronchospasm in patients without asthma history, rescue inhaler use, emergency room visits, and hospital admissions for asthma in wildfire areas. However, healthcare professionals can help mitigate the effects through communication and public health measures.
One great resource is an educational pamphlet from the American Thoracic Society (ATS), which advises patients with chronic pulmonary diseases on managing their health during wildfire events. For those in wildfire areas, it recommends planning early evacuation, establishing a clean room with recirculating air conditioning or an air purifier, following a care plan, and having backup medication. Healthcare professionals should familiarize themselves with these recommendations to share with at-risk patients.
Other Resources for Poor Outdoor/Indoor Air Quality Days
Healthcare professionals should be familiar with and offer other resources to patients on staying safe during poor air quality days. The American Lung Association (ALA) provides information on outdoor air quality and a source for healthcare professionals to advocate for improving air quality through the Healthy Air Campaign. In addition, the ALA provides a list of 10 tips to protect against poor air quality. The ATS created an educational pamphlet for managing indoor air quality, offering measures to ensure minimal exposure to irritants, triggers, and pollution. Similarly, Carlsten et al. summarize the evidence for improved air quality measures.
Finally, increasing awareness through local weather forecasts and API alerts is key to helping patients take appropriate preventative measures and maintain good health. The Environmental Protection Agency site, AirNow.gov, localizes the weather report and offers excellent air quality information.
The Need for Greater Advocacy
One final point is the importance of advocacy from healthcare professionals for clean air policies to improve patient lives. The 2012 ATS Workshop Report offers an excellent example of advocacy — the document was developed following a workshop bringing together experts from vital professional societies and government agencies to address critical threats to global respiratory health posed by climate change.
As witnessed in the U.S. after the Clean Air Act of 1970, air quality improvements can reduce the related disease burden. A recent report from the Environmental Committee of the Forum of International Respiratory Societies details how local, regional, national, and worldwide efforts have impacted health outcomes. Healthcare providers can influence and change this dangerous arc to decrease morbidity and save lives.
Amy M. Schaller MSRC, RRT-ACCS, and Joseph P. Coyle, MD, are members of the American Association for Respiratory Care.