Wildfires' Impact On California's Air Quality And Pollution

California's wildfires have had a significant impact on air pollution and public health. The fires emit various pollutants, including carbon compounds and particulate matter and other fire-related atmospheric pollutants. In 2020, California's wildfires emitted an estimated 9 million metric tons of carbon dioxide, contributing to the state's overall emissions increase of about 30%. Wildfire smoke contains toxic substances such as carbon monoxide and benzene, and soot particles that can enter airways and lungs, triggering asthma and heart attacks and causing other severe health conditions. The smoke also affects the environment, with nitrogen dioxide emissions contributing to the formation of ozone and particulate matter, which can lead to respiratory issues and harm crops. While some experts argue that carbon emissions from wildfires are part of a natural cycle and should not be considered net contributors to climate change, others maintain that all carbon emissions contribute to the issue.

Wildfires increase the release of nitrogen oxides (NOX) and reactive organic gases (ROG)

Wildfires have had a significant impact on air quality in California, with smoke spreading across the state and even reaching neighbouring states. The smoke released during wildfires contains harmful substances such as carbon monoxide, benzene, and tiny particles of soot, which can have serious health impacts.

One of the key ways in which wildfires contribute to air pollution is through the release of nitrogen oxides (NOX) and reactive organic gases (ROG). These compounds are known as precursors to ozone formation and secondary particulate matter (PM2.5). During wildfire outbreaks, extreme biomass burning (BB) emissions occur, releasing both oxidized and reduced forms of nitrogen compounds. The oxidized nitrogen compounds include nitrogen oxides (NOX), which are formed by the combination of nitric oxide (NO) and nitrogen dioxide (NO2). The reduced forms include ammonia (NH3). High emissions of these compounds are a major concern for air quality and have detrimental consequences for both human and ecosystem health.

The release of nitrogen oxides and reactive organic gases during wildfires has been the subject of several studies. Research on the 2020 wildfires in California found that wildfires emitted nitrogen oxides at a rate comparable to that of anthropogenic emissions. However, the emission of reactive organic gases from wildfires was significantly higher, more than five times the amount released by anthropogenic sources. This highlights the significant impact of wildfires on the release of these specific pollutants.

The increase in nitrogen oxides and reactive organic gases during wildfires has important implications for air quality and public health. These compounds are precursors to the formation of ground-level ozone, which is a major component of smog. Ground-level ozone is a harmful pollutant that can irritate the respiratory system and exacerbate respiratory conditions such as asthma. Additionally, the release of these compounds can contribute to the formation of secondary particulate matter (PM2.5), which refers to fine particles with a diameter of less than 2.5 micrometres. These fine particles can remain suspended in the air for extended periods and have the potential to travel long distances, impacting air quality over large areas.

The impact of wildfires on the release of nitrogen oxides and reactive organic gases has significant short-term and long-term effects on air pollution and public health. The immediate consequences include reduced air quality, respiratory issues, and increased risk of asthma or heart attacks. Over the long term, the accumulation of these pollutants can contribute to climate change and have lasting impacts on ecosystems and human health. Therefore, it is crucial to continue monitoring and mitigating the effects of wildfires to minimize their impact on the environment and human well-being.

The health impacts of wildfire smoke

Wildfire smoke is a complex mixture of gaseous pollutants, hazardous air pollutants (HAPs), water vapour, and particle pollution. It contains harmful substances such as carbon monoxide, benzene (a carcinogen), and tiny particles of soot. While carbon emissions from wildfires might not be a significant concern due to the natural cycle of carbon in the atmosphere, wildfire smoke still poses a serious health risk.

Particle pollution is the primary public health threat from exposure to wildfire smoke. These particles, also known as particulate matter or PM, are a mixture of solid and liquid droplets suspended in the air. The particles come in various sizes and shapes due to their different sources. Some particles are so minuscule that they are only visible under an electron microscope. Fine particles, generally 2.5 micrometres or smaller in diameter, are of the utmost health concern. They comprise about 90% of the total particle mass in wildfire smoke. Ultrafine particles, with diameters less than 0.1 micrometres, also fall under this category.

The health effects of particle pollution exposure can vary from relatively minor to severe. Minor health effects include eye and respiratory tract irritation. More serious consequences can include exacerbating asthma and heart failure, and even leading to premature death. Even short-term exposure to wildfire smoke can have detrimental health impacts. Fine particles are respiratory irritants, and exposure to high concentrations can cause persistent coughing, phlegm, wheezing, and breathing difficulties. Even healthy individuals can experience transient reductions in lung function and pulmonary inflammation when exposed to fine particles.

People with chronic conditions are at an elevated risk of adverse health effects from wildfire smoke. This includes individuals with asthma, Chronic Obstructive Pulmonary Disease (COPD), diabetes, chronic kidney disease, or heart disease. Wildland firefighters are another group at high risk of health complications from prolonged and continuous exposure to wildfire smoke. Studies have indicated a potential cumulative effect of smoke exposure on their lung function, with some research reporting a progressive decline during burn seasons.

The California wildfires have significantly impacted air quality and public health. In 2020, the wildfires in California broke the annual record for the area burned, shrouding the Bay Area in smoke and pushing air pollutant concentrations to hazardous levels. The direct emissions of PM2.5 from these wildfires were nearly nine times greater than those from anthropogenic sources. On the highest emission day, September 9, 2020, when the August Complex Fire and the Creek Fire peaked, PM2.5 emissions from the wildfires were 38 times the average emissions from human-caused sources. Additionally, wildfires emit reactive organic gases (ROG) at rates more than five times higher than anthropogenic sources, contributing to ozone formation and secondary PM2.5.

Wildfires and climate change

Wildfires have been a natural part of many ecosystems and are beneficial to some forest and grassland ecosystems. However, the combination of climate change and historical fire suppression has led to larger, more frequent, and more destructive fires.

Climate Change and Wildfires

Climate change is a key factor in increasing the risk and extent of wildfires in the Western United States and other parts of the world. Warmer temperatures, reduced precipitation, and higher atmospheric thirst due to climate change have led to warmer and drier conditions, creating longer and more active fire seasons. These conditions have increased the drying of organic matter, or fuel, in forests, making them more susceptible to fires.

Research by the U.S. Forest Service found that fire seasons are starting earlier in the spring and extending later into autumn. Parts of the Western United States, Mexico, Brazil, and East Africa now have fire seasons that are more than a month longer than they were 35 years ago. The warming climate has particularly impacted the temperate conifer forests of the Western U.S. and the boreal forests of northern North America and Russia, with warmer nighttime temperatures allowing fire activity to persist overnight.

Wildfires and Air Pollution

Wildfires emit various pollutants that contribute to air pollution and have significant health impacts. Wildfires emit fine particulate matter (PM2.5), carbon compounds, reactive organic gases (ROG), nitrogen oxides (NOX), and other fire-related atmospheric pollutants. These emissions can increase air pollutant concentrations to hazardous levels, affecting air quality over large areas. The smoke released during wildfires contains toxic substances such as carbon monoxide, soot particles, and benzene, which can trigger asthma or heart attacks and pose risks to public health.

California Wildfires

California, in particular, has been severely impacted by wildfires and the resulting air pollution. The 2020 California wildfires set a record for the annual area burned and significantly increased emissions of PM2.5 and ozone precursors. These wildfires sent an estimated 9 million metric tons of carbon dioxide into the atmosphere, equivalent to the emissions of about 1.9 million cars in a year. The UCLA and University of Chicago researchers concluded that the 2020 wildfires increased overall emissions by about 30%, making them California's second-largest source of greenhouse gases after transportation.

While some experts argue that carbon emissions from wildfires are part of a natural cycle and should not be considered net contributors to climate change, others emphasize that these emissions still contribute to the overall carbon balance. The California Air Resources Board estimates emissions from wildfires but does not include them in the state's greenhouse gas targets for 2030.

Wildfires' contribution to air pollution in remote forests

Wildfires in California have had a significant impact on air pollution, with smoke spreading across the state and affecting the air quality in remote forests and populated areas alike. The smoke released during these fires contains a complex mixture of pollutants, including particulate matter (PM2.5), carbon compounds, and other fire-related atmospheric pollutants.

PM2.5 refers to fine particulate matter with a diameter of 2.5 micrometres or less. These particles are hazardous to human health as they can penetrate deep into the lungs and even enter the bloodstream, affecting various organs. Short-term exposure to wildfire smoke containing PM2.5 can cause mild irritation, such as runny noses and scratchy throats, as well as more severe conditions like bronchitis. The risks are even higher for sensitive groups, including children, the elderly, pregnant people, and those with pre-existing respiratory and cardiovascular issues.

The contribution of wildfires to air pollution in remote forests has been quantified through various methods. One approach involves employing wildfire emissions and chemical transport models to simulate the impact on PM2.5 levels. For example, Shi et al. (2019) examined the impact of wildfires in Southern California in 2017 using satellite-based techniques and a chemical transport model to estimate emissions and their effect on PM2.5 concentrations. Another method utilises direct measurements from ground-based or satellite observations to map pollutant concentrations and attribute a portion to wildfires. Wang et al. (2021) and Enayati Ahangar et al. (2022) employed this approach to study the impact of wildfires on air quality in California.

The impact of wildfires on air pollution in remote forests is also assessed through the use of low-cost sensor networks, such as the PurpleAir network, which provides real-time data on PM2.5 concentrations. These sensors, although low-cost, help to enhance the modelled PM2.5 concentrations and provide valuable information for understanding the impact of wildfires on air quality. For instance, Enayati Ahangar et al. (2022) used PurpleAir sensors to study PM2.5 concentration mapping over California's San Joaquin Valley during the 2020 wildfire season.

In addition to the direct impact on air pollution, wildfires also contribute to climate change by releasing carbon dioxide and other greenhouse gases into the atmosphere. While some experts argue that carbon emissions from wildfires are part of a natural cycle and should not be considered net contributors to climate change, others maintain that all carbon emissions contribute to the overall problem. California's wildfires in 2020 emitted an estimated 9 million metric tons of carbon dioxide, equivalent to the annual emissions of about 1.9 million cars. These emissions are erasing the state's hard-fought climate gains, with wildfires being the second-largest source of greenhouse gases in the state that year, after transportation.

The role of CAMS in tracking wildfire emissions and air quality impacts

The Copernicus Atmosphere Monitoring Service (CAMS) plays a crucial role in tracking wildfire emissions and their impact on air quality. CAMS uses the Global Fire Assimilation System (GFAS) to estimate emissions of carbon compounds, particulate matter, and other fire-related atmospheric pollutants. GFAS utilises near-real-time satellite observations of Fire Radiative Power (FRP) from NASA MODIS instruments on the Terra and Aqua satellites. FRP is a measure of the radiative heat output from active fires, which is then used to calculate the emissions of greenhouse gases and other pollutants that constitute wildfire smoke.

CAMS provides regular and up-to-date information on the location, intensity, and estimated emissions of wildfires worldwide. It also tracks smoke transport and composition, including the movement and composition of smoke plumes. This information is vital for governments, organisations, and individuals to assess and mitigate the impacts of wildfires. For instance, during the 2020 California wildfires, CAMS data showed enhancements in PM2.5 surface concentrations, aerosol optical depth (AOD), and other constituents associated with wildfire smoke near Los Angeles. CAMS alerts highlighted the smoke outflow from the fires towards the Pacific Ocean, enabling local populations to limit their exposure.

CAMS offers historical datasets and analysis of wildfire emissions, allowing for the study of their long-term effects on air quality. This open-access data informs emergency response strategies, regulatory measures, and scientific research. By integrating atmospheric monitoring with technology, CAMS helps mitigate public health risks and safeguard the environment. For example, CAMS data revealed that the 2020 California wildfires emitted nitrogen oxides (NOX) at a rate comparable to anthropogenic emissions, while reactive organic gas (ROG) emissions were five times higher. These gases are precursors to ozone formation and secondary PM2.5, which can have significant health impacts.

Additionally, CAMS contributes to global wildfire monitoring by providing data through maps and graphs. This information assists local governments in fine-tuning fire management policies and bolstering efforts to mitigate harmful wildfires and smoke. For instance, CAMS data has been crucial in understanding the impact of wildfires in regions like Brazil, Bolivia, Spain, France, India, and Russia. By tracking wildfire emissions and air quality impacts, CAMS plays a vital role in helping communities and policymakers make informed decisions to protect public health and the environment.

Frequently asked questions