Los Angeles Air Pollution: What's In The Air?

Los Angeles, California, is known for its smog, a combination of particle and ozone pollution. The city's air quality is among the worst in the United States, with 9 of the 15 most polluted cities in the country located in the greater Los Angeles county. The air pollution in Los Angeles is mainly caused by the burning of fossil fuels, especially by vehicles, ships, planes, and manufacturing, as well as wildfires. The large population of 4 million in Los Angeles, with another 6 million in the surrounding county, contributes significantly to the city's air pollution due to heavy vehicular emissions and traffic congestion. Despite efforts to reduce pollution over the years, Los Angeles continues to face air quality issues, with adverse health effects on its residents, especially children.

Los Angeles has the worst ozone air pollution in the US

Los Angeles, California, is notorious for its smog, a combination of particle and ozone pollution. The city has consistently ranked as one of the most polluted regions in the United States. According to the 2019 State of the Air report, Los Angeles had the worst ozone air pollution in the country. The report compared data across 229 metropolitan areas, and Los Angeles stood out for its high levels of ozone, a harmful gas pollutant.

Ozone pollution, often referred to as "bad ozone," is formed when sunlight reacts with nitrogen oxides and organic substances. Vehicle exhaust is a significant source of these pollutants, so traffic is frequently identified as a leading contributor to ozone pollution. The burning of fossil fuels by vehicles, ships, planes, and manufacturing industries also plays a role in Los Angeles' poor air quality. The city's large population of about 4 million residents, with another 6 million in the surrounding Los Angeles County, further exacerbates the issue with heavy vehicular emissions and traffic congestion. It is estimated that there are approximately 6.5 million vehicles in Los Angeles alone.

The health implications of ozone pollution are significant. Ozone can cause respiratory infections and inflammation, and prolonged exposure can lead to lung damage and even premature death. According to the County of Los Angeles Public Health Department, 1 in 10 children in the county have been diagnosed with asthma, and the overall risk for cancer is increased by 900 per million, as reported by the South Coast Air Quality Management District. The combination of warm weather and harmful pollutants from fuel emissions makes Southern California particularly susceptible to high ozone levels.

While there have been efforts to improve air quality in Los Angeles, the city continues to face challenges. The South Coast Air Quality Management District has taken legal action against the U.S. Environmental Protection Agency, arguing that their policies make it impossible to achieve clean air standards in the Los Angeles area. Despite some improvements in ozone levels, Los Angeles still struggles with air pollution, and it remains crucial to address this issue for the well-being of its residents.

Vehicle emissions are a major contributor to LA's air pollution

Los Angeles has long been associated with smog and poor air quality. While the air quality has improved over the last few decades, LA still has the worst ozone air pollution in the United States.

The high traffic density in LA means that vehicle emissions are an even greater contributor to the city's air pollution. There are an estimated 6.5 million vehicles in LA, and nationwide, cars and trucks contribute to more than 50% of carbon monoxide emissions. While lead emissions from vehicles have decreased with the phasing out of leaded gasoline, cars and trucks are still a major source of nitrogen oxides, which contribute to ozone pollution.

California's restrictions on vehicle emissions have been effective in reducing organic aerosol pollution in LA. A study by UC Berkeley scientists found that concentrations of PM2.5 in the Los Angeles basin in 2012 were half of what they were in 1999. This has resulted in fewer PM2.5 violations, and overall, a significant improvement in air quality.

Despite this progress, vehicle emissions still play a significant role in LA's air pollution. The South Coast Air Quality Management District has sued the US Environmental Protection Agency, arguing that emissions from aircraft, locomotives, and vessels under federal jurisdiction will increase by nearly 10% between 2012 and 2023, making it difficult for LA to meet clean air standards.

The health implications of LA's air pollution are severe

Los Angeles has long been known for its smog, a combination of particle and ozone pollution. The city's air quality is heavily influenced by its large population of 4 million, with another 6 million in the surrounding county, contributing to heavy vehicular emissions and traffic congestion. The burning of fossil fuels, especially by vehicles, ships, planes, and manufacturing, as well as wildfires, are significant factors in the city's air pollution.

Ozone, a gas pollutant formed when sunlight reacts with nitrogen oxides and organic substances, is another major contributor to LA's air pollution. Ground-level ozone is a harmful pollutant that inflames the linings of the lungs and damages lung function. Like PM2.5, ozone exposure can lead to respiratory infections, inflammation, and premature death. The Children's Health Study (CHS), conducted in Southern California, has investigated the long-term consequences of air pollution on the respiratory health of children, highlighting the severe health risks that air pollution poses to younger individuals.

Carbon monoxide, a product of burning fossil fuels, is another pollutant of concern in LA. When inhaled, it enters the bloodstream and interferes with oxygen transport, causing symptoms such as headaches and fatigue, and more severe issues in individuals with heart disease. Lead, while less prevalent due to the phasing out of leaded gasoline, still poses a threat, with emissions from industrial processes and non-road equipment contributing to elevated blood lead levels and associated health issues.

While efforts to reduce air pollution in LA have shown some progress, the health implications of the city's air pollution remain a severe issue that requires continued attention and action.

Wildfires contribute to LA's air pollution

Los Angeles is known for its smog, a combination of particle and ozone pollution. The city's air pollution is among the worst in the United States, with the county experiencing hazardous air quality levels. The region has long failed to achieve ozone standards set by the federal Clean Air Act. Wildfires contribute significantly to this poor air quality.

In January 2025, Los Angeles experienced one of the most devastating wildfire outbreaks in its history. The fires, fuelled by strong, dry Santa Ana winds, low soil and vegetation moisture, and a period of scarce rainfall, ravaged over 40,000 acres, resulting in unprecedented destruction, casualties, and mass evacuations. These wildfires had a severe impact on the air quality in the region.

Wildfire smoke contains a complex mixture of particles and gases, including particulate matter, gases, chemicals, heavy metals, asbestos, PFAS, microplastics, and other toxic pollutants. These pollutants pose significant health risks to residents, both short and long-term. In the immediate aftermath of exposure, individuals may experience irritation of the eyes, nose, and throat, coughing, wheezing, shortness of breath, headaches, and fatigue. For those with pre-existing respiratory conditions, such as asthma or COPD, wildfire smoke can trigger exacerbations, leading to increased medication usage and potential hospitalization.

The long-term health effects of prolonged or repeated exposure to wildfire smoke are particularly concerning. Studies suggest that such exposure may contribute to the development of chronic respiratory conditions and increase the risk of heart disease. Urban wildfires, in particular, create a uniquely dangerous mixture of pollutants due to the burning of buildings, vehicles, and manufactured products containing toxic chemicals.

Researchers are actively studying the impact of wildfire pollution on Los Angeles' air quality and the resulting health consequences for residents. The Los Angeles Fire Human Exposure and Long-Term Health Study (L.A. Fire HEALTH Study) is analyzing outdoor and indoor air samples to guide safe reentry and cleanup procedures following the wildfires. Additionally, a team of university researchers has launched a 10-year project to examine the long-term health impacts of pollution from the recent wildfires, including the effects on respiratory, neurological, cardiovascular, immune, and reproductive systems.

LA's air quality has improved over the last 30 years

Los Angeles is notorious for its poor air quality, which is among the worst in the United States. The city's air pollution is primarily attributed to the burning of fossil fuels, vehicle emissions, and traffic congestion. The combination of particle and ozone pollution creates the infamous smog that Los Angeles is known for. Despite this, Los Angeles's air quality has shown significant improvement over the last three decades.

In the 1960s, California began addressing air pollution by establishing the California Air Resources Board (CARB), an organization dedicated to researching and implementing effective air pollution policies. The Clean Air Act, along with its amendments in 1977 and 1990, played a crucial role in establishing federal air quality monitoring, emission control, and enforcement. The 1990 amendments, in particular, contributed significantly to the improvement of air quality in Los Angeles over the past 30 years.

Year-over-year trends in Los Angeles have shown promising results. From 2017 to 2018, there was a 10.6% reduction in air pollution, followed by an additional 11.8% decrease from 2018 to 2019. The COVID-19 pandemic also had an unexpected positive impact on air quality. During the lockdown period in March 2020, Los Angeles experienced its longest stretch of clean air since at least 1995 due to reduced economic activity and fewer vehicles on the road.

While Los Angeles still struggles to meet the national air quality standards for PM2.5 and ozone, there has been undeniable progress. The Clean Air Action Plan of 2006 has led to an 87% reduction in particulate matter and a 58% decrease in nitrogen oxides from port operations, a significant source of pollution in the city. Additionally, the phasing out of leaded gasoline has resulted in a dramatic decline in lead emissions from cars and trucks.

Despite these improvements, air pollution remains a pressing issue in Los Angeles. The city continues to face challenges in reducing emissions from aircraft, locomotives, and oceangoing vessels, which fall under federal jurisdiction. The South Coast Air Quality Management District has taken legal action against the U.S. Environmental Protection Agency, arguing for the necessity of reducing these emissions to meet clean air standards. As Los Angeles continues to combat air pollution, the health of its residents remains a key concern, with asthma and increased cancer risks prevalent in the area.

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