The air is thick and stifling. Flames leap up the trees and tear through dry brush, fueling them further, and smoke plumes rise high above. This imagery is is likely familiar to most by now, seared into minds with its constant presence in national news and Smokey Bear ads. But days later, and hundreds or even thousands of miles away, pollutants hang in the air, causing numerous unforeseen health consequences such as increased respiratory issues and mortality rates.
Wildfires in the Western U.S. are increasingly common with the decadal averages of large fires increasing and the average wildfire season lengthening significantly over the past three to four decades (1). The vulnerability of forests to large fires has been amplified by lengthened, climate change-induced droughts which weaken trees against pest infestation and, in turn, increase dead tree matter (2).
These trends are projected to continue due to higher average temperatures and more rapidly melting snowcaps. The subsequent issues are not unique to the western U.S., either, as smoke constituents from wildfires have the potential to cross enormous distances. Smoke from fires in California this August had noticeable impacts on air quality even in Missouri and as far east as New York and Massachusetts, according to the National Weather Service (3).
Wildfire impact can be felt primarily through direct exposure to flames and radiant heat or through indirect exposure to bushfire smoke and combustion by-products, and the water or soil contaminated by them (4). Bushfire smoke, generated largely by the burning of vegetation and wood, features particulate matter as its main air pollutant. Notably, it produces PM2.5 (particulate matter 2.5 micrometers or less in diameter) which can be deposited deep within the lungs and whose increased presence is linked to many adverse health effects including increased mortality. One 2009 study in Finland placed the increase in mortality between 0.5 and 2 percent for each increase of 10 micrograms per cubic meter of urban PM2.5 (5). In contrast, a UK report placed the increase at as high as six percent (4). For bushfire generally, a 2011 study examining mortality rates in Sydney over a 14-year period found that days with high air pollution from bushfires and dust storms correlated with, among other adverse health impacts, a 5% increase in non-accidental mortality (6). Wildfire smoke, and the accompanying particulate matter, can linger for days or even months depending on the scope of the fire, rendering its ill effects all the more troubling (7).
There are also populations whose physiological factors leave them more vulnerable to environmental exposures than others. This includes children, those who are pregnant, and older adults. Children’s greater air intake in relation to body weight as well as pregnant women’s increased respiratory rate increases exposure to air pollutants (7). A lone 2012 study conducted in Southern California also indicated potential of reduced birth weight as a result of prenatal wildfire smoke exposure, which fits into well-documented evidence of low birth weight from exposure to cigarette smoke or ambient particulate matter while in utero (8). In older populations, pre-existing respiratory and cardiovascular diseases may worsen with exposure to wildfire smoke (4).
This latest string of large wildfires in the U.S. easily blends into a backdrop of increased occurrence, intensity, and unpredictability of natural disasters due to the disruption of familiar climate systems. They represent a substantial public health concern as is, and the threat of their damage will only grow with the direction of increased global warming. Mitigating damage from these natural disasters will require proactive scenario planning in the coming decades and calls for greater collaboration and emergency preparation between lawmakers, healthcare providers, and climate researchers.
Edited by: Chase Breimeier
Illustrated by: Lily Xu