Los Angeles Air quality today

Why does Los Angeles get so much smog?

Ozone is a gas that forms in the air when two kinds of pollution, nitrogen oxides and volatile organic compounds, react in sunlight ^[2]. These come from many sources, including vehicles, consumer products, industry and plants ^[2]. Ground-level ozone is also known as smog ^[1].

The area is the nation's second largest urban area, and it puts out a large amount of emissions ^[2]. Low winds slow their spread, and frequent strong temperature inversions form a cap that traps them close to the ground ^[2]. The surrounding mountains trap pollution further as the sea breeze pushes it inland, and abundant sunshine drives the reactions that form ozone ^[2].

When is the air worst in Los Angeles?

High ozone is typically seen from April through October, when days are longer and sunlight is stronger ^[2]. The highest levels usually come on the hottest summer days, because the reactions run faster in heat ^[2]. The local air district marks May as the start of smog season, which officially ends on September 30, though high ozone may persist into the fall ^[3].

Ozone often reaches unhealthy levels in the afternoon, especially in inland areas ^[3]. In 2020, coastal areas saw the fewest days over the federal ozone standard, because the sea breeze carries pollution inland before it turns into ozone ^[2]. Ozone rose toward the Riverside and San Bernardino County valleys and nearby mountains ^[2].

Fine particles, called PM2.5 because they are less than 2.5 microns across, can be high at any time of year ^[2]. They tend to peak most often in fall and winter, when still air traps pollution ^[2].

How bad is it compared with the rest of the US?

In the American Lung Association's 2026 State of the Air report, based on 2022 to 2024 data, Los Angeles-Long Beach ranked as the most ozone-polluted city in the US, with 159.2 unhealthy ozone days a year ^[1]. It ranked 7th worst for year-round particle pollution, and 7th for short-term particle spikes, with 13 unhealthy days a year ^[1].

There is progress too. The same report lists Los Angeles among seven California communities that reached their lowest annual particle pollution levels ^[1].

In its 2022 plan, the regional air district noted that the Los Angeles basin and the San Joaquin Valley were the only areas with an extreme rating for failing the federal 2015 ozone standard ^[2].

How does wildfire smoke affect Los Angeles?

The Palisades and Eaton fires both began on January 7, 2025 ^[5]. In a January 9, 2025 advisory, the air district reported PM2.5 levels from Unhealthy for Sensitive Groups up to Hazardous in Malibu, Pacific Palisades and central and southwest Los Angeles County ^[4]. Gusty Santa Ana winds also contributed to high levels of windblown dust and ash ^[4].

Air monitors in the smoke plume from January 7 to 11, 2025 found highly elevated toxic metals such as arsenic and lead, even compared with other fires in the region that burned in non-urban areas ^[5]. After January 12, these metals dropped sharply, to levels generally similar to before the fires ^[5].

The air district also says the region had unusually high ozone in 2020 because of record-breaking heatwaves and wildfires ^[2].

What is being done about it?

The South Coast Air Quality Management District is the agency responsible for improving air quality across large parts of Los Angeles, Orange, Riverside and San Bernardino counties ^[3]. Its 2022 Air Quality Management Plan is focused on strategies to meet the federal 2015 ozone standard ^[2].

After the January 2025 fires, the district ran a 19-week expanded air monitoring effort at the Eaton and Palisades burn areas, testing for particles, toxic metals and asbestos ^[5]. It reported that results did not show levels of concern, even during peak debris removal, and it ended this monitoring on July 8, 2025 ^[5].

How to protect yourself in Los Angeles

During smog season, check the AQI, a daily air quality score, to plan outdoor exercise ^[3]. On unhealthy days, limit outdoor activity, especially in the afternoon when ozone peaks, and avoid heavy exertion near busy roads ^[3]. Young children, older adults, pregnant people and people with chronic breathing conditions may feel effects even at low pollution levels ^[3].

When wildfire smoke drifts in, US EPA advice is to stay inside with the doors and windows closed and use a portable air cleaner powerful enough for the room ^[6]. Choose one that makes little or no ozone ^[6]. Avoid adding to indoor pollution: skip candles, incense, fireplaces and cooking at high heat ^[6].

If you must be outside in smoke, EPA says a snug-fitting N95 respirator reduces your exposure to the fine particles, and that dust masks and bandanas should not be relied on ^[6]. Avoid strenuous activity and wait until the air is better before being active outdoors ^[6].