Wildfires and Respiratory Illness: Implications for the COVID-19 Pandemic

Posted on Behalf of  Ricardo Ramirez, Hannah Allen, Olivia Leleck

As described in our previous blogs (see Wildfire Smoke as an Occupational Health Hazard: Safety Guidance Featured, and Wildfire Smoke as an Occupational Health Hazard: Regulatory Update and Current State of the Science), increasing temperatures and dry conditions have contributed to longer, more destructive fire seasons in the Western U.S., and their effects are becoming increasingly pervasive. Acute and chronic exposures to the pollutants found in wildfire smoke at sufficient levels may result in adverse health outcomes, such as lung irritation, inflammation, and immune system effects, which may increase susceptibility to respiratory illnesses such as SARS-CoV-2, the virus that causes COVID-19 (CDC, 2020a). As the Western U.S. is experiencing one of the worst wildfire seasons on record, with approximately nine million acres burned in 2020 to date, questions are being raised about the impact that exposure to wildfire smoke may have on the COVID-19 pandemic, especially when compounded by the flu season (National Interagency Fire Center, 2020).

Under certain conditions, heightened particulate matter (PM) concentrations from wildfires may increase the risk of respiratory effects, such as asthma exacerbation, and may be associated with increased respiratory-related emergency department visits and hospitalizations (Alman, et al., 2016; Reid, et al., 2019). A number of studies published within the last year have found statistically significant relationships between constituents of wildfire smoke, such as PM2.5, and respiratory outcomes – including flu and pneumonia cases (Landguth et al. 2020), the incidence of acute respiratory infections (Stowell et al. 2019), and COVID-19 case counts and case-fatality rates (Isphording & Pastel, 2020; Wu, et al., 2020; Yao, et al. 2020; Zhu, et al., 2020). Since this evidence is still emerging, there is uncertainty with regard to:

  1. Whether preexisting conditions exacerbated by air pollution elicit a worse immune response to respiratory viruses, including SARS-CoV-2,
  2. The extent to which air pollution influences community transmission of SARS-CoV2, or
  3. If these factors compound each other to worsen the prognosis of COVID-19.

Additional evidence is needed to confirm the biologic plausibility of the relationship between air pollutants from wildfires and COVID-19. However, given the severity of the two events independently, it is important for policymakers, businesses, and the general public to take the risk of their combined forces seriously, and take proactive approaches to mitigate these risks.  

As flu season begins and COVID-19 cases remain high in the U.S., the association between wildfire smoke exposure and respiratory illness is particularly concerning. COVID-19 infections and deaths are projected to continue to increase this winter, with worse scenarios predicted if areas ease mandates, such as social distancing, limited venue capacity, and mask use (Institute for Health Metrics and Evaluation). Many groups at high risk for respiratory effects from wildfire smoke are also at an increased risk for severe COVID-19 illness and flu complications, including older adults, people with chronic health conditions, and immunocompromised individuals (CDC, 2020a; CDC, 2020b; CDC, 2020c). The increasing frequency and intensity of wildfires highlight the need to ensure high-risk groups are not adversely affected by poor air quality produced by fires, a point that cannot be overstated while the COVID-19 pandemic continues to severely affect people with health vulnerabilities. In addition to health effects, wildfires can also bring social situations that may increase the risk of contracting COVID-19, such as staying in a public disaster shelter or checking in on friends and neighbors (CDC, 2020a). Dual outbreaks of flu and COVID-19 in the coming months could result in coinfection with both viruses and further overwhelm healthcare systems (JAMA, 2020).

While emergencies such as the COVID-19 pandemic and wildfires cannot always be avoided, businesses can prepare and protect employees by developing comprehensive risk management and response plans. Such efforts will need to be flexible and capable of being altered to accommodate (1) changing community risk levels for COVID-19 resulting from fluctuations in the prevalence of community spread, the potency of circulating strains, and/or pharmaceutical interventions, (2) changes in airborne concentrations of  PM2.5 and other constituents associated with wildfire smoke, (3) individual risk factors associated with severe adverse health effects from COVID-19 and other respiratory viruses (e.g., the flu virus), and exposure to wildfire smoke, (4) evolving best practices intended to help protect workers and the public, and (5) other issues, such as shortages of mask and respirator supplies and exhausting the healthcare system’s capacity to provide care. Business leaders should remain vigilant and flexible in their emergency response and develop risk mitigation strategies that consider the joint risks wildfire smoke and the flu may have on the pandemic.

Cardno ChemRisk is experienced in developing and assisting with COVID-19 risk management and response plans for a variety of industries (e.g., media and television, food and beverage manufacturers, construction, and retailers). Cardno ChemRisk scientists have also evaluated exposure profiles and dose-response relationships for complex mixtures resulting from wildfires, air pollution, and industrial emissions. To learn more about the ways Cardno ChemRisk can support your business, please contact Rachel Zisook and Natalie Egnot, or visit our website.