How California's Air Became So Polluted

California has some of the worst air quality in the US, with more than 3,800 people dying prematurely each year due to air pollution. The state's air pollution is caused by a combination of factors, including vehicular emissions, fossil fuel production, and prolonged wildfire seasons due to climate change. The transportation industry is a major contributor to atmospheric pollution, with Los Angeles and its surrounding areas having a high concentration of vehicles—more than one car for every two people. Additionally, the state's geographical features, such as the basin-like structure of Los Angeles surrounded by mountains, can trap ozone, smog, and other toxic particles, further exacerbating the problem. While California has implemented aggressive emissions policies and regulations, racial and socioeconomic disparities persist, with low-income communities of color continuing to be disproportionately affected by air pollution.

Wildfires

California's air quality is affected by several factors, with wildfires being a significant contributor. The state experiences frequent and severe wildfires that release hazardous fine particles into the atmosphere, leading to increased pollution levels. These particles are small enough to bypass the body's upper respiratory defences and reach the alveoli, the delicate membranes in the lungs responsible for gas exchange. The smoke from wildfires contains gases, vapours, and particles that can remain airborne for extended periods, impacting both nearby and downwind regions.

The particles in wildfire smoke are up to ten times more harmful than smoke from everyday sources like traffic or industry. This smoke contains toxic compounds, including carbon monoxide, oxides of nitrogen, formaldehyde, and acrolein, which are similar to those found in cigarette smoke. Additionally, the tiny soot particles in wildfire smoke are considered especially hazardous as they can enter airways, lodge in lungs, and trigger asthma or heart attacks. Wildfire smoke also has negative effects on the heart, brain, immunity, and other vital organs and bodily systems.

The increasing frequency and intensity of wildfires in California are likely due to climate change. As forests burn, carbon dioxide and other greenhouse gases are released into the atmosphere, disrupting the natural cycle of chemical absorption and release. While some experts argue that these emissions 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.

The impact of wildfires on air quality can be seen in California's recent history. In 2020, the state experienced its worst wildfire season on record, with over two million acres burned. This resulted in hazardous levels of air pollution, with the Air Quality Index (AQI) exceeding 500 in several regions, well above the unhealthy threshold of 200. The smoke from these fires had a significant impact on people's health, and the number and severity of fires have continued to worsen in subsequent years.

Addressing climate change and reducing greenhouse gas emissions are crucial steps in combating air pollution from wildfires. Additionally, adopting cleaner energy sources and implementing initiatives to regulate and reduce industrial and vehicular emissions can help improve California's air quality on a larger scale.

Industrial emissions

California's air pollution has been a public health concern for decades, with residents complaining about its side effects as early as 1943. Industrial emissions are a significant contributor to this issue. Various industrial processes release numerous air pollutants that negatively impact the health of California residents. Fine particulate matter (PM2.5) and ozone are two of the most concerning pollutants from a public health perspective.

PM2.5 is released directly into the atmosphere through the combustion of fuels such as gasoline, oil, diesel, and wood. It is also formed through atmospheric chemical reactions of precursors emitted from combustion sources, including motor vehicles. Diesel engines, in particular, are a significant source of PM2.5 pollution. Exposure to PM2.5 has been linked to increased risks of preterm birth and adverse effects on children's lung function growth, with higher levels of air pollution associated with more asthma cases in children.

Ozone, while protective of the environment against powerful ultraviolet rays, can be harmful to human health in excess. It is a major constituent of smog and is formed through complex atmospheric reactions with chemicals emitted from motor vehicles and other combustion sources. The unique geographical location of Los Angeles, situated in a basin between mountains, contributes to stagnant atmospheric conditions that trap ozone, smog, and other toxic particles, creating a "pollution dome" over the city. This dome enhances the concentration of greenhouse gases, including methane and carbon dioxide, which have been detected by satellite observations.

California's industrial emissions are not limited to a single sector but are diverse and far-reaching. The state's commitment to reducing climate-changing emissions is evident through initiatives like the California Global Warming Solutions Act (AB 32) and the annual statewide greenhouse gas (GHG) emission inventory. The inventory provides estimates of anthropogenic GHG emissions, including carbon dioxide, methane, nitrous oxide, and fluorinated gases with high global warming potentials.

While regulatory efforts have been made to address air pollution, rollbacks on emission standards and enforcement of polluting industries have also occurred. For example, during the Trump administration, there were 16 regulatory rollbacks on air pollution and emissions, with more in progress, which weakened governmental emission standards and oversight. These actions have likely contributed to the stagnation or worsening of air quality levels in many Californian cities in recent years.

Climate change

California's air quality is a complex issue with a variety of contributing factors, and climate change is one of the key factors exacerbating the problem. The state's unique geography and weather patterns also play a significant role.

One of the primary effects of climate change in California is the increase in temperature and changes in precipitation patterns. Warmer temperatures contribute to the formation of ground-level ozone, a major component of smog. Ozone is formed when sunlight reacts with volatile organic compounds (VOCs) and nitrogen oxides (NOx), which are emitted from vehicles, industrial activities, and natural sources. As temperatures rise, the chemical reactions that produce ozone are accelerated, leading to higher concentrations of this harmful pollutant. In addition, changes in precipitation patterns can affect the frequency and intensity of wildfires, which are a significant source of smoke and particulate matter in the air. Warmer and drier conditions create a more favorable environment for wildfires to start and spread, further degrading air quality.

The impact of climate change on wind patterns also influences California's air pollution. The state's mountainous regions and coastal areas experience a phenomenon known as "temperature inversion," where a layer of warm air traps cooler, denser air close to the ground. This creates a stable atmosphere that prevents pollutants from dispersing effectively. As climate change alters wind patterns, it can lead to more frequent and persistent inversion layers, resulting in the accumulation of pollutants and the deterioration of air quality, particularly in valleys and basins.

Another consequence of climate change is the potential for increased dust and particulate matter from drought-stricken areas. As temperatures rise, certain regions may experience more frequent and prolonged droughts, causing soil to dry out and become susceptible to wind erosion. Fine dust particles can be blown over large distances, contributing to reduced air quality in populated areas. These particles not only have direct health impacts but also serve as a surface for chemical reactions that produce additional pollutants.

The effects of climate change on California's air quality highlight the interconnectedness of environmental issues. While the state has made significant strides in reducing emissions and improving air quality over the years, the ongoing changes in climate present new challenges. Addressing these challenges requires a comprehensive approach that targets both emissions reductions and the mitigation of climate change impacts. This includes implementing policies and technologies to reduce greenhouse gas emissions, as well as adapting to the changing conditions through strategies such as improved wildfire management, drought response, and air quality monitoring and forecasting systems.

Nitrogen oxide emissions

There are several factors contributing to the high levels of NOx emissions in California. One significant source is wildfires, which have become increasingly frequent and intense due to climate change. As wildfires burn across the state, they release NOx into the atmosphere, leading to higher levels of ozone and other air pollutants. The impact of wildfires on NOx emissions is expected to worsen in the coming years, with researchers predicting that "in another 10 or 20 years, vast tracts of California will have burned, and those emissions are going to affect the chemistry of our atmosphere immensely."

Soil emissions are another critical source of NOx in California. Nitrogen oxide is naturally present in the soil and can be released into the air through various processes, such as the metabolism of nitrogen by soil microbes. Agricultural practices, particularly the use of nitrate-containing fertilizers, also contribute significantly to NOx emissions from soils. Researchers have found that soil emissions of NOx increase with higher temperatures, and climate change is expected to lead to warmer and drier conditions, further exacerbating this issue.

The impact of NOx emissions on air quality and public health is a significant concern in California. High levels of ozone and particulate matter in the air can cause various health issues, including burning lungs, irritated eyes, coughing, nausea, and increased asthma cases in children. The California Air Resources Board (CARB) has established health-based ambient air quality standards to protect the public from the harmful effects of air pollution, including NOx emissions. However, despite efforts to improve air quality, many cities in California continue to experience stagnated or worsening air quality levels due to factors such as wildfires and regulatory rollbacks on emission standards.

While wildfires and soil emissions are natural sources of NOx, human activities have also played a role in reducing emissions through the implementation of stringent environmental regulations. However, the recent rollbacks on air pollution regulations and the increasing frequency of wildfires due to climate change are threatening to undo the progress made in reducing NOx emissions. As a result, NOx emissions are once again becoming a significant challenge for California, impacting the health and well-being of its residents.

Poor energy sources

California's poor air quality has been a problem since 1943, when residents first complained of smog causing burning lungs, irritated eyes, coughing, and nausea. The state's air pollution has numerous causes, one of which is poor energy sources.

California is the home of one of the largest container ports in the Western Hemisphere, the Port of Los Angeles, as well as 12 airports with major cargo operations. These commercial activities make up about a third of the state's economy but are responsible for half of its air pollution. The transportation industry is a major source of harmful emissions, contributing about 40% of the state's atmospheric pollution. Diesel particulate matter, for instance, is responsible for 520 per million cancer cases in the state. The state's commercial activities, along with its transport industry, have led to high emissions of nitrogen oxide, a major component of smog, which is detrimental to children and the elderly.

The state's energy demands are also met through fossil fuels, which are a significant source of air pollution. Fossil fuel production and vehicular emissions are major contributors to unhealthy air quality in California. The state's energy demands are also met by hydropower, which is, however, affected by droughts, which are expected to reduce energy generation and increase natural gas-fired power and electricity prices.

The state's energy mix, therefore, contributes to its poor air quality. However, California has made significant progress in terms of clean energy. In 2018, Governor Jerry Brown issued an Executive Order to achieve carbon neutrality by 2045 and maintain net negative emissions thereafter. The state has increased investments in renewable energy, particularly solar, and in 2022, generated enough renewable power to meet 103% of consumer demand in just a day.

Frequently asked questions