Wildfire smoke has acute cardiorespiratory impact, but long-term effects still under study

The 2019 wildfire season is underway in many locales across the United States, exposing millions of individuals to smoky conditions that will have health consequences ranging from stinging eyes to scratchy throats to a trip to the ED for asthma or chronic obstructive pulmonary disease (COPD) exacerbation. Questions about long-term health impacts are on the minds of many, including physicians and their patients who live with cardiorespiratory conditions.

^{US Forest Service photo courtesy of Peter Buschmann.}

The Woolsey Fire as seen from Topanga, Calif., on Nov. 9, 2018. The wildfire burned more than 96,000 acres and destroyed more than 1,600 structures.

John R. Balmes, MD, a pulmonologist at the University of California, San Francisco, and an expert on the respiratory and cardiovascular effects of air pollutants, suggested that the best available published literature points to “pretty strong evidence for acute effects of wildfire smoke on respiratory health, meaning people with preexisting asthma and COPD are at risk for exacerbations, and probably for respiratory tract infections as well.” He said, “It’s a little less clear, but there’s good biological plausibility for increased risk of respiratory tract infections because when your alveolar macrophages are overloaded with carbon particles that are toxic to those cells, they don’t function as well as a first line of defense against bacterial infection, for example.”

The new normal of wildfires

Dr. John R. Balmes

Warmer, drier summers in recent years in the western United States and many other regions, attributed by climate experts to global climate change, have produced catastrophic wildfires (PNAS;2016 Oct 18;113[42]11770-5; Science 2006 Aug 18;313:940-3). The Camp Fire in Northern California broke out in November 2018, took the lives of at least 85 people, and cost more than $16 billion in damage. Smoke from that blaze reached hazardous levels in San Francisco, Sacramento, Fresno, and many other smaller towns. Other forest fires in that year caused heavy smoke conditions in Portland, Seattle, Vancouver, and Anchorage. Such events are expected to be repeated often in the coming years (Int J Environ Res Public Health. 2019 Jul 6;16[13]).

^{Courtesy Dr. Wayne Cascio}

On Nov. 10, 2018, wildfire smoke from the devastating Camp Fire obscured views of the Golden Gate Bridge from Lands End Trail in San Francisco.

Wildfire smoke can contain a wide range of substances, chemicals, and gases with known and unknown cardiorespiratory implications. “Smoke is composed primarily of carbon dioxide, water vapor, carbon monoxide, particulate matter, hydrocarbons and other organic chemicals, nitrogen oxides, trace minerals and several thousand other compounds,” according to the U.S. Environmental Protection Agency (Wildfire smoke: A guide for public health officials 2019. Washington, D.C.: EPA, 2019). The EPA report noted, “Particles with diameters less than 10 mcm (particulate matter, or PM₁₀) can be inhaled into the lungs and affect the lungs, heart, and blood vessels. The smallest particles, those less than 2.5 mcm in diameter (PM_2.5), are the greatest risk to public health because they can reach deep into the lungs and may even make it into the bloodstream.”