Whereas poor air quality is often thought to be the result of industrial pollution, particularly in developed countries, extreme heat, drought, and wildfires are playing an increasingly important role in the deterioration of air quality in the United States. According to a new report by First Street entitled “Atrocious Air,” air pollution is predicted to increase by as much as 50% in the Western United States over the next 30 years, largely due to climate change. This air pollution is primarily in the form of growing pockets of exposure to ozone and from upticks in particulates (known as PM 2.5) generated from wildfire smoke.
In California alone, the state now averages just 93 days a year classified as “Green Days” (no threat from air pollution) while Red Days (air quality is rated as “unhealthy”) have increased by 459%. According to First Street, approximately 10% of all households in the United States already suffer at least one week or more every year from exposure to unhealthy air as a result of wildfire smoke, with some of the most at-risk areas being large population centers such as San Francisco, Sacramento, and Seattle.
Air pollution and human health
The two biggest air pollutants that negatively affect human health in the United States are ozone (also known as O3) and PM 2.5. The acronym PM stands for particulate matter (a mixture of solid particles and liquid droplets in the air) while the number 2.5 refers to the fact that these particles are 2.5 microns in diameter or smaller. For comparison, a single human hair is around 70 micrometers in diameter or 30 times larger than a 2.5 PM particle.
It is precisely the small size of PM 2.5 particles that make them so dangerous for human health. These particles are easily inhaled and then can penetrate deep into the lungs or even enter the bloodstream. According to the World Health Organization, exposure to air pollution is responsible for chronic obstructive pulmonary diseases (COPD), lung cancer, and pneumonia and can also cause heart diseases, neurological disorders (such as strokes), and damage to reproductive systems.
While PM 2.5 particles are generated from high-density manufacturing sites, power plants, and vehicular exhaust systems, they also rise significantly during wildfires as vast quantities of smoke and finely charred particles are ejected into the atmosphere.
Exposure to ozone (O3), on the other hand, is largely related to changes in air temperature and humidity. In short, hotter and drier air increases the amount of ozone at ground level. According to the CDC, exposure to ozone can lead to headaches, coughing, shortness of breath, fluid build-up in the lungs, and even asthma.
Climate change is reversing progress on air quality
In the United States, a series of federal regulations have been enacted to address air quality concerns, starting with the Clean Air Act of 1963 and the Air Quality Act of 1967, which largely were established to reduce air pollution from industrial sources and vehicle emissions. In 1970, the Environmental Protection Agency (EPA) was established, which developed an Air Quality Index (AQI) to more easily track and understand the six major contributors to air pollution.
Fig.1. Trends in major air pollutants milestones
Source: Atrocious Air
However, while great strides have been made to reduce air pollution from industrial sources and vehicle emissions, changes in environmental conditions, including extreme heat, drought, and wildfires are now contributing to the increase of PM 2.5 and ozone.
Significantly, wildfires do not just affect communities in the immediate vicinity of the blaze. For instance, the smoke from Canadian wildfires in the summer of 2023 resulted in New York City seeing its air pollution record broken by 126 AQI points, temporarily giving the city the worst air quality on the entire planet.
The negative offset to the reduction of industrial and vehicular sources of air pollution caused by climate change is known as the “climate penalty,” with wildfires being the primary contributor of such. As such, First Street has been calling on the federal government and state legislatures to take steps to prevent climate change-fueled wildfires. First Street also recommends that Americans should consider moving away from areas with poor air quality (or avoid moving to those areas in the first place).
Wildfires are increasing in frequency and intensity
According to the First Street and the National Oceanic and Atmospheric Administration (NOAA), the primary reason why wildfires are increasing, particularly in the Western part of the United States, is the hotter and drier conditions caused by climate change as well as land management practices. Over time, hot and dry conditions lead to a rise in flammable organic material which then increases both the frequency and the severity of wildfires.
According to one study that looked at wildfires in the western United States between 2008 and 2012, more than 25% of all PM 2.5 air pollution was directly attributable to wildfires. Another study, conducted in 2021, found that there was a 270% increase in the number of people experiencing an “extreme smoke day” (air quality classified as unhealthy for all age groups) over the previous decade. And in 2020, more than 25 million people in the United States were exposed to dangerous levels of PM 2.5 from wildfire smoke.
From a climatological standpoint, increased air temperatures and sustained periods of heat result in lower levels of moisture and humidity. Together, these combine to increase exposure to ozone as well as higher levels of dry organic materials that go on to fuel wildfires.
More information
First Street is a registered 501(c)(3) charity whose mission is to “leverage” climate science and engineering to quantify the risk for every property in the United States, and they publish an air quality report annually. Residents of the United States can consult the government website AirNow to get real-time data about the air quality at their location.
