Data provided by
|3||Pacific Palisades Highlands|
|5||Harvard Westlake Upper School|
|7||CCA - Ewing and Valentine|
|10||Meadow Valley Terrace|
(local time)SEE WORLD AQI RANKING
live AQI index
|Air pollution level||Air quality index||Main pollutant|
|Moderate||61 US AQI||PM2.5|
|Close your windows to avoid dirty outdoor air|
|Sensitive groups should reduce outdoor exercise|
|Saturday, Sep 26|
Moderate79 US AQI
|Sunday, Sep 27|
Moderate70 US AQI
|Monday, Sep 28|
Moderate73 US AQI
|Tuesday, Sep 29|
Good47 US AQI
Moderate92 US AQI
|Thursday, Oct 1|
Unhealthy for Sensitive Groups129 US AQI
|Friday, Oct 2|
Unhealthy183 US AQI
|Saturday, Oct 3|
Unhealthy194 US AQI
|Sunday, Oct 4|
Unhealthy153 US AQI
|Monday, Oct 5|
Moderate90 US AQI
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Los Angeles air quality averages a US AQI or air quality index rating of “moderate.” Monthly averages in 2019 varied from AQI 32 (“good”) in February to AQI 64 (“moderate”) in November. Despite seemingly optimistic ratings, Los Angeles’s air pollution is among the worst in the United States, both for PM2.5 and ozone.
PM2.5 is airborne particulate matter measuring up to 2.5 microns in size. It is widely regarded as one of the most harmful pollutants to human health for its prevalence at dangerous levels. Exposure to PM2.5 has been linked to health effects such as heart disease, respiratory illness, and premature death.
For PM2.5, the greater Los Angeles county contains 9 of the 15 most polluted cities in the United States, according to the 2019 World Air Quality Report. In this same report, the city of Los Angeles ranked 82nd in the US (out of 1,517 included cities). Its annual average, however, differed by only 4 micrograms from the number one most polluted city in the U.S.: Portola, California.
According to the 2019 State of the Air report, which compared data across 229 metropolitan areas, Los Angeles has the worst ozone air pollution in the United States. Ozone is a gas pollutant formed when sunlight reacts with nitrogen oxides and organic substances. Vehicle exhaust contains both the nitrogen oxides and reactive organic substances needed to form ozone, so traffic is frequently identified as a leading source. Like PM2.5, ozone can cause health effects ranging from respiratory infections and inflammation to premature death.
Together, PM2.5 and ozone form the smog that Los Angeles is often known for. The summer months of June, July, and August tend to be more polluted than other months for both PM2.5 and ozone. This is because of drier conditions, less rainfall, higher temperatures, and a higher frequency of wind-blown dust and wildfires fanned by the Santa Ana winds.
Los Angeles does not currently meet the U.S. EPA’s national air quality standards for both PM2.5 and ozone.1 The associated health implications are evident in the numbers. According to the County of Los Angeles Public Health Department, 1 in 10 children have been diagnosed with asthma.2 Overall risk for cancer, meanwhile, is increased by 900 for every million, according to the South Coast Air Quality Management District.
Air pollution data is an important resource for taking action to mitigate these health effects. Refer to the top of this page for Los Angeles’s forecast air quality data and real-time air quality data.
Los Angeles air quality has dramatically improved over the last 30 years because of the 1990 amendments to the Clean Air Act. Most recently, year-over-year trends have resulted in reductions in L.A. air pollution of 10.6% from 2017 to 2018, and another 11.8% from 2018 to 2019.
Data collected by EPA governmental monitors and analyzed in the COVID-19 Air Quality Report found that Los Angeles experienced a long stretch of WHO-target air quality (< 10 μg/m3) from March 7-28, 2020, its longest streak since at least 1995. This 18-day stretch of exceptionally clean air is likely the result of lockdown measures put in place to reduce the spread of the COVID-19 pandemic, during which non-essential businesses were ordered to close and residents were urged to stay at home. March 2020 became Los Angeles’s cleanest air quality month on record, averaging PM2.5 levels of 5.6 μg/m3 (US AQI 23).
Yearly averages are often dependent on the wildfire season, which can contribute to greatly elevated periods of city-wide air quality. The last three years have seen fewer state-wide forest fires and burned acreage, though wildfires are expected to increase in frequency over the long term as temperatures rise droughts become longer.
Los Angeles is a city notorious for its smog, a combination of particle and ozone pollution. The prevalence of these pollutants result from many factors, including 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 Los Angeles county, contributes significantly to the its ‘nonattainment’ air quality status because of heavy vehicular emissions and traffic congestion. It is estimated that there are 6.5 million vehicles in the city of Los Angeles alone. Current mayor Eric Garcetti set forth a sustainability plan that seeks to increase zero-emission vehicles in the city, growing their share from 1.4% in 2018 to 25% by 2025, and 100% by 2050.3 Power consumption, BBQs, and other such personal local emissions are also a major source of air pollution as a result of the city’s population.
Los Angeles’s shipping industry is another key contributor, particularly in recent years as trade with Asia has expanded. The Port of Los Angeles and the Port of Long Beach are the two busiest container ports in the United States. 4 Many port operations rely on fossil fuel or diesel to power ships, trucks, and other transportation. Since the implementation of the Clean Air Action Plan of 2006, particulate matter (PM) from these operations has dropped by 87%, while nitrogen oxides, an important precursor pollutant to ozone, are down 58%. Still, the ports remain a significant pollution source, producing an estimated 100 tons of smog daily, with little year-over-year improvement since 2011. The Los Angeles air pollution map often reveals higher AQI in Los Angeles’s port areas. Port authorities are looking for new ways to further decrease these emissions, such as investing cleaner energy transport vehicles.
Although they’re temporary and sporadic, wildfires often impact yearly average air pollution in Los Angeles. A combination of dry conditions, highly flammable fuels (such as the volatile Douglas fir and ponderosa pine tree species), increasingly hot summers, steep mountains, and strong Santa Ana winds combine to make the area highly susceptible to large and severe wildfires.
The geography of Los Angeles, in a basin surrounded by mountains, is further conducive to trapping air pollution. While many locations around the world commonly experience temperature inversions in the winter, Los Angeles often experiences a similar effect in warmer months. This happens when relatively warm air from the Great Basin or inland Los Angeles traps cooler, ocean air close to the Earth’s surface, preventing polluted air from rising and dispersing. This type of temperature inversion is called a marine inversion. The Los Angeles marine inversion can often be attributed to the layer of haze shrouding downtown buildings in pictures from the famous Hollywood sign.
+ Article Resources
 California non-attainment/maintenance status for each county by year for all criteria pollutants. (2020).
 Mazza S. (2018, August 7). Investigation finds LA Harbor-area smog challenges grow as new health threats emerge.
 Roth S. (2019, May 6). Los Angeles sets dramatic new goals for electric cars.
 Vock DC. (2019, June). Can America’s biggest ports go green?