Los Angeles Air Pollution: Causes And Effects Explained

Los Angeles, California, is known for its entertainment businesses, Hollywood, and the American film industry. However, in recent years, it has become equally well-known for its poor air quality. Los Angeles' air pollution is among the worst in the United States, with the county containing 9 of the 15 most polluted cities in the country. The air pollution in Los Angeles is caused by various factors, including vehicle emissions, manufacturing, wildfires, and heatwaves. The basin-like shape of the city also traps ozone pollution, keeping it in the air.

Vehicle emissions

The high traffic density in Los Angeles exacerbates the problem, as cars and trucks contribute to more than 50% of all emissions nationwide, and this percentage is even greater in cities. The large population of 4 million people in LA, with another 6 million in the surrounding county, significantly contributes to heavy vehicular emissions and traffic congestion. The city's basin-like geography also traps ozone pollution, keeping it stagnant and concentrated.

A UCLA-led study found that disadvantaged communities in Los Angeles face higher levels of toxic air pollution. The study, which measured air pollution toxicity against people's socioeconomic conditions, revealed that those living in the most disadvantaged areas experienced about 65% higher toxicity than those in the most advantaged groups. This disparity is attributed to the fact that disadvantaged areas not only have worse environments but also lack access to healthcare and good nutrition, increasing their health risks.

The transportation sector in Los Angeles is working towards reducing emissions. The Los Angeles Metropolitan Transportation Authority aims to use more fuel-efficient vehicles and adopt renewable energy sources. Additionally, there is a goal to reduce emissions by 40% by the year 2030 and continue the search for renewable resources, such as electricity.

Industrial emissions

The sheer number of motor vehicles in Los Angeles County is also a major factor in its air pollution issues. With a large population of 4 million, and another 6 million in the surrounding county, heavy vehicular emissions and traffic congestion are a significant concern. The commute by vehicle is the principal form of transportation in the city, so the emissions from cars will continue to fill the air until better solutions are implemented. Motor vehicles are the largest source of carbon monoxide emissions, and in cities like Los Angeles, with its high traffic density, their contribution to air pollution is even more pronounced.

The Los Angeles-Long Beach-Riverside area ranked as the most ozone-polluted city in 2013, and the city of Los Angeles itself ranked 82nd in the US out of 1,517 cities in the 2019 World Air Quality Report. The report also stated that the greater Los Angeles county contains 9 of the 15 most polluted cities in the United States.

While there have been improvements in recent decades, the worsening air pollution in Los Angeles has caused serious issues for the climate and the health of its residents. The city's basin-like shape traps the ozone pollution, keeping it in the air. The "bad" ozone, which is man-made and found at ground level, causes serious health issues, including asthma attacks, coughing, and wheezing. It also contributes to heart attacks, strokes, and premature death.

To combat this, the city has set goals to reduce emissions by 40% by 2030 and to continue the search for renewable resources, such as electricity. The Los Angeles Metropolitan Transportation Authority is also working to improve air quality by using more fuel-efficient vehicles and adopting renewable energy sources.

Wildfires

Los Angeles, California, is known for its poor air quality. While the city has seen improvements in recent decades, the region has become well-known for its air pollution. In January 2025, wildfires in Los Angeles caused unprecedented destruction in urban areas, resulting in 24 casualties and mass evacuations. Fuelled by strong, dry Santa Ana winds, low soil and vegetation moisture, and a long period of scarce rainfall, the wildfires rapidly spread and released significant amounts of carbon and air pollutants, with potential environmental impact and health risks.

Wildfire smoke typically carries with it noxious gases and particulate matter that make it more toxic than normal air pollution. It contains small particles, gases, and water vapour. The primary health concern is the small particles, which can cause burning eyes, a runny nose, a scratchy throat, headaches, and illnesses such as bronchitis. The particulate matter in wildfire smoke has been linked to higher rates of heart attacks, strokes, and cardiac arrests, and weakened immune systems. It can also contribute to respiratory illness and premature death. The concentration of fine particulate matter in the Los Angeles area during the January 2025 wildfires reached alarming levels, with potential fatal consequences.

The smoke from the wildfires blanketed the city, turning the air brown and lung-burning. It caused an eye-watering haze and made it difficult to breathe. Schools cancelled classes, and officials issued air quality alerts. The smoke from the wildfires was blown out towards the Pacific Ocean, but it still impacted the air quality in Los Angeles and the surrounding areas. The city's geography and weather conditions, including strong winds, made it difficult for the smoke to disperse, resulting in slowly accumulating pollution levels.

The impact of wildfire smoke on air quality can be monitored and tracked using satellite imagery and systems such as the Copernicus Atmospheric Monitoring Service (CAMS) and the Global Fire Assimilation System (GFAS). These systems provide data on wildfire emissions, air quality, and potential health risks. The data is used to inform emergency response strategies, regulatory measures, and scientific research to help mitigate the impacts of wildfires on public health and the environment.

Geography and weather

Los Angeles, California, is internationally known for its entertainment businesses, Hollywood, and the American film industry. However, it has also gained a reputation for its poor air quality. LA's air quality averages a US AQI rating of "moderate", and in 2019, the greater Los Angeles county contained 9 of the 15 most polluted cities in the United States. LA's unique geography and weather conditions significantly contribute to its air pollution problem.

LA's basin, a dip in the Earth's surface shaped like a bowl, traps ozone pollution and keeps it in the air. The 'good' ozone layer high in the atmosphere protects the Earth from too much UV radiation, but the 'bad' ozone, which is man-made and low to the ground, is extremely harmful. It causes health problems such as coughing, wheezing, and asthma attacks, and can even contribute to heart attacks, strokes, and premature death.

The region's geography and weather conditions also make it difficult for smoke from wildfires to disperse, resulting in slowly accumulating pollution levels until the fire stops burning or the wind changes direction. Wildfires have become increasingly common in the area due to anthropogenic climate change, and the smoke they produce fills the LA basin with pollutants. Sunlight and heat can also cause some gas pollutants, such as nitrogen dioxide and volatile organic compounds, to chemically react and form ground-level ozone, a harmful secondary pollutant.

The large population of LA, with 4 million people in the city and another 6 million in the surrounding county, contributes to heavy vehicular emissions and traffic congestion. The city's warm, Mediterranean climate encourages the use of cars as the principal form of transportation, and the thick, stagnant air traps emissions from cars, contributing to the city's poor air quality.

Socioeconomic factors also play a role in the geography and weather of LA's air pollution. A UCLA-led study found that disadvantaged communities in LA experience higher levels of toxic pollution, which compounds other public health challenges such as limited access to healthcare and good nutrition.

Fertilized land

Los Angeles, California, is known for its entertainment businesses, Hollywood, and the American film industry. However, it has also gained notoriety for its poor air quality. LA's air quality averages a US AQI or air quality index rating of "moderate", and the city's air pollution is among the worst in the United States, particularly for PM2.5 and ozone.

While factors such as vehicular emissions, manufacturing, wildfires, and climate change have been identified as major contributors to LA's air pollution, another significant source may lie in the fertilized soil of the nearby Salton Sea air basin. This basin, located about 100 miles east of San Diego in the Colorado Desert, is one of the most polluted regions in the nation.

The heavily irrigated and fertilized soil in this region creates ideal conditions for plants, but it also fuels the activity of soil bacteria that release smog-forming pollution. Research from UC Davis suggests that the soil in the Salton Sea air basin emits more than 11 tons per day of nitrogen oxides, contributing to the formation of smog. This finding emphasizes the need to better understand agricultural land management practices and their impact on air quality.

Excess fertilizer application can produce up to five times more smog-forming nitrogen oxides. Fertilizer sales in Imperial County, which includes the Salton Sea area, have more than doubled since 1991. The use of fertilizers and irrigation has transformed the harsh Colorado Desert into verdant fields, but it has also contributed to the region's poor air quality.

While Los Angeles has made improvements in air quality over the last few decades, the recent spike in pollution highlights the need for continued efforts to address this issue. By understanding the role of fertilized land in air pollution, steps can be taken to mitigate its impact and improve the health and environmental outcomes for the region.

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