Particulate Pollution (PM2.5) Concentrations in the United States, 2020
As wildfires rage in California again this summer, they are engulfing regions with deadly particulate pollution that could impact the life expectancy of residents. AQLI’s most recent report shows that in 2020—a year in which California’s wildfires killed 30 people and economic losses totaled more than $19 billion—more than half of all Californian counties experienced their worst air pollution since satellite measurements began collecting data in 1998. Indeed, some counties are now more polluted than they were in 1970, before policy existed to reduce pollution.
California leads the nations as the most polluted state thanks mostly to the catastrophic wildfires. Out of the top 30 most polluted counties in the United States, 29 of them were in California in 2020. The pollution levels, if sustained, are set to shave nearly a year off the life expectancy of residents on average in each of those counties. The most polluted county was Mariposa, which experienced a particularly bad wildfire season in 2020. Mariposa generally has cleaner air than nearby Fresno and neighboring Madera and Merced counties, which are more steeply situated in the foothills, more densely populated, and therefore more exposed to fossil fuel emissions in addition to the wildfire smoke. But in 2020, pollution in Mariposa shot up to its highest level on record, averaging 22.6 μg/m3—double the second highest pollution level recorded in 2018. If this high pollution continues, residents of Mariposa could live 1.7 years less than if the county met the World Health Organization guideline for what is considered a safe level of pollution.
While fossil fuels are not the direct cause of this pollution spike in 2020, they ultimately provided the spark. As the planet becomes hotter, drier soil and drought conditions expose more areas to wildfire risks. Indeed, rampant wildfires have not just been a hallmark of California’s summers in recent years. They have run rampant in regions throughout the world, from Greece and France to Indonesia and the Congo Basin. Each time there is an increase in wildfires, particulate pollution surges. Given the role climate change will play in exacerbating air pollution, with an increase in extreme wildfires being a poignant example, it is imperative that policies are introduced to reduce the burning of fossil fuels.