Amidst California’s ongoing battle against the growing threat of wildfires, studies continue to indicate the detrimental effects of wildfire smoke on public health – as well as what can be done.
Wildfires are not a new form of natural disaster, by any means. However, the blazes that have raged across much of California, and the rest of the world from Australia to Brazil, have done so with increasing intensity in the last decade.
That timespan alone has seen eight – nine, if you extend back to August 2012 – of the 10 largest wildfires in California’s history when measured by acreage burnt, according to Cal Fire records. Even more strikingly, four of the top five have struck since August 2020, with 2020 and 2021 marking the two years with the highest acres burnt state-wide.
But what has been the driving force behind this sharp increase in wildfire activity?
The total acres burned by California wildfires has spiked in recent years. California’s Office of Environmental Health Hazard Assessment’s “Indicators of Climate Change in California” report (Fourth Edition, 2022).
A recipe for disaster
“In pretty much every single way, a perfect recipe for fire is just kind of written in California,” said Park Williams, a bioclimatologist at the Lamont-Doherty Earth Observatory at Columbia University.
One ingredient in that recipe is drought, which has of course been at the root of much of this uptick in both fire frequency and ferocity.
In an all-encompassing climate report released in Nov. 2022 by California’s Office of Environmental Health Hazard Assessment, OEHHA), state scientists have dubbed the years from the turn of the century until 2021 part of a new “megadrought” era, standing as “the driest 22-year period in the past millennium.”
Beginning in 2020, California wilted under its most recent drought as the state suffered its two worst wildfire years on record. It is only in recent months, amidst a flurry of atmospheric rivers and stormier winter conditions, that the drought has begun to loosen its grip.
Prior to that – and still, in the drier regions of the state yet to be granted a reprieve – soil and vegetation dried up without relief from regular rainfall. In turn, sections of the sprawling forest that decorates the state dried up too, adding to a stockpile of dead, flammable material which could provide ample fuel, should a stray spark catch alight.
Climate change has also resulted in increasing annual average temperatures state-wide, as indicated in that same OEHHA study. The study’s findings revealed that eight of the ten warmest recorded years came in that same ten-year span between 2012 and 2022, coinciding with the period of the state’s most devastating wildfires.
California’s annual average temperatures are trending upwards. California’s Office of Environmental Health Hazard Assessment’s “Indicators of Climate Change in California” report (Fourth Edition, 2022).
Warmer temperatures have combined with droughts to further amplify the volume of plant matter which withers and accumulates, awaiting even the slightest of poorly placed sparks from either anthropogenic (human-originating activity) sources, like a smouldering campfire, or natural ones, like a strike of lightning.
In the conditions that warm, drought-struck shrubbery can provide, one spark can be enough. The flames that burst forth are often caught by the likes of Santa Ana and Diablo winds.
Santa Ana winds are gusts that flow westward from high air pressure regions around the Santa Ana Mountains inland in Southern California, to lower pressure regions off of California’s coasts, while Diablo winds originate in similarly high-pressure zones near the Diablo mountain range in Northern California and flow into lower pressure areas around the San Francisco Bay Area.
Both currents are warm and dry, and as they rush across the land to alleviate the pressure gradient previously mentioned they can drastically accelerate a fire’s progression.
However, these flames themselves, while presenting significant threats to property, land, and life directly, are only part of the problem that faces those in a wildfire’s path.
Air pollution, and a tiny but mighty threat
“Wildfires are becoming an increasingly important driver of air pollution,” said Dr. Sam Heft-Neal, a research scholar at Stanford University’s Center on Food Security and the Environment.
Wildfire smoke alone typically contributes a quarter of total air pollution, in the form of PM2.5 (fine particulate matter) emissions, in the United States each year, according to EPA findings in the last decade.
A multi-institutional paper published in 2021 and co-authored by Heft-Neal, found that on the west coast that figure may rise to a staggering 50 % – a marked increased from the same figure a decade ago, which lay under 20 %.
These PM2.5 are fine particles in the air that have a diameter of less than 2.5 micrometers, making them significantly thinner than a human hair.
Particulate matter size comparison diagram. United States Environmental Protection Agency
Heft-Neal explained that through imposing regulations focused on lower emissions from, for example, the fossil fuel industry, legally enforced by policies such as the Clean Air Act, the United States had been succeeding at improving air quality by lowering levels of PM2.5 over the last few decades.
However, this progress has begun to “hit a wall,” Heft-Neal said.
And when wildfire activity spiked, with nature’s wrath significantly harder to regulate than human industries, the substantial improvements that had been made began to be reversed.
A product of combustion (from burning just about anything), PM2.5 are the most abundant pollutant found in the plumes of smoke that billow from wildfires.
Accordingly, the level of PM2.5 (in an air quality index, AQI) is also a metric by which the production and movement of these smoke trails are measured and tracked by scientists. Typically, readings of 35 μg/m3 and above over a 24-hour period indicate unhealthy air quality.
But of all the reasons that one wouldn’t want to find themselves in close proximity to these wildfires, you may be thinking, “how could something that small pose a threat?”
Larger particles (for example, those with a diameter greater than 10 micrometers) present risks mainly as irritants to the eyes, nose and throat.
But smaller particulate matter, like the PM2.5 found in smoke, can cause a multitude of potential health problems upon exposure and inhalation, increasing in severity the longer one is exposed to said smoke.
Primarily, health concerns from PM2.5 inhalation involve damage to the respiratory system. Due to their size, these particles can travel deep into the lungs, increasing the risks of impaired lung function, asthma attacks and the development of conditions such as acute bronchitis. The irritation caused by this may also increase susceptibility to respiratory infections, including but not limited to COVID-19.
Sometimes, this particulate matter may even enter the bloodstream, where it could cause similar impaired functionality of other vital organs including the heart, particularly in those with underlying conditions.
Illustrating this, a working paper helmed by Heft-Neal just last month indicated that visits to hospital emergency departments increase by up to 110% in the week following one “extreme smoke day” for ailments most closely associated with short-term air pollution exposure, such as asthma, chronic obstructive pulmonary disease (COPD) and cough.
In California during the assessed period between 2006-2017, the paper’s authors estimated in total “that smoke exposure was responsible for roughly 3,000 additional emergency department visits per year.”
Managing an increasing issue
To reduce the risks of these adverse health effects in the event of wildfires, it is therefore crucial to limit exposure to this smoke as much as possible.
Such preventative measures during wildfire events generally come down to simply “asking individuals to protect themselves,” Heft-Neal said, explaining that such guidance should typically consist of wearing masks, using air purifiers, and staying inside as much as possible when increased air pollution from wildfire activity is observed or reported. It is also important to limit physical activity, as exercise causes increased lung function, presenting greater opportunities for these dangerous particles to be inhaled and inflict damage.
Unfortunately, communities and individuals of differing economic statuses often have different resources to protect themselves.
One effort that some local municipalities are taking is the provision, or designation, of Clean Air Centers – public buildings which are meant to provide higher quality, filtered and purified air to members of the public who require their use during wildfires events or other instances of heightened air pollution.
In terms of reducing differences between economic groups that are impacted disproportionately by wildfires and the air pollution caused by wildfire smoke, Heft-Neal believes that providing resources to aid one’s ability to enact these self-protective measures such as masks and air purifiers is the most necessary action.
Following wetter weather in recent months, climate scientists and researchers – including Heft-Neal – expect that this upcoming wildfire season may, thankfully, be milder than that which California experienced in 2020 and 2021.
However, this heightened rainfall will of course in turn give way to greater plant growth. In an increasingly warm environment (and potential future droughts), this plant matter will itself dry, die and accumulate, causing a possible future surge in wildfire fuel availability.
Locally, Brad Eggleston, the Director of Public Works for the City of Palo Alto, shared via email that Palo Alto has “a multi-functional team that works on wildfire reduction programs,” which include wildfire prevention education and an annual wildfire mitigation plan. The latter, which is require by California state law, must be updated every year and revised every three years, Eggleston said.
Currently, ongoing prevention methods by the city include “increased vegetation management” and electric line inspections (powerlines are another common culprit for wildfire initiation), as well as prioritized maintenance in the Foothills park area, where Eggleston added that the Fire Department inspects all houses each year between May and June.
To continue to mitigate the risks of future wildfires to evolving into more and more catastrophic events, local governments, public bodies and regulatory agencies likely must devise ways to implement existing strategies of fuel removal such as forestry trimming and prescribed burns in more economically friendly ways.
In the case of these wildfires that cause drastic declines in air quality, meanwhile, provision of Clean Air Centers, masks and air purifiers, should also be a priority, to reduce the detrimental impacts PM2.5 can have however possible.
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Alex Dakers is an M.A. Journalism student at Stanford University, with a BSc (Hons) in Biomedical Science from the University of Bath. Using his background in science, Alex is interested in reporting on issues including environmental justice, and in particular the intersection between environmental science and public health. A former collegiate swimmer, Alex is also a staff writer for The Stanford Daily’s sports section, as well as a contributor to the Peninsula Press.
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