What Is the Air Quality in Los Angeles, California?
Los Angeles, California has an Air Quality Grade of D (poor) with a 5-year median AQI of 75. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been improving over the past decade.
Los Angeles, California Air Quality Snapshot
| Air Quality Grade | D36/100 |
| 5-Year Median AQI | 75 (Moderate) |
| Most Recent Median AQI (2023) | 67 (Moderate) |
| Dominant Pollutant | Fine Particulate Matter (PM2.5) |
| 10-Year Trend | Improving (-0.94 AQI/yr) |
| Unhealthy Days (last 5 yr) | 501 |
| National Rank (cleanest = #1) | #1015 of 1,020 (100th most polluted percentile) |
| California Rank | #50 of 53 |
What Does the D Grade Mean?
Los Angeles, California earns a D — air quality falls below the U.S. average, with a 5-year median AQI of 75. Residents with asthma, COPD, heart disease, or young children should watch daily AQI forecasts and limit outdoor exertion when alerts go out.
Los Angeles, California's 5-year median AQI of 75 is 34 points above the national average of 41 — meaningfully more polluted than the typical U.S. metro tracked here. Within California, Los Angeles, California runs more polluted than the state average of 49 — local sources or geography are concentrating pollution above the state's typical reading.
For context within California: Humboldt, California currently holds the state's cleanest grade (A, AQI 28), while Inyo, California sits at the bottom (F, AQI 57).
What's in Los Angeles, California's Air?
The dominant pollutant in Los Angeles, California is Fine Particulate Matter (PM2.5). Fine particulate matter — particles less than 2.5 micrometers across — comes mostly from combustion: vehicle exhaust, wildfire smoke, residential wood burning, and industrial emissions. Because these particles are small enough to enter the bloodstream, PM2.5 is the pollutant most strongly linked to cardiovascular disease, respiratory illness, and premature death.
Days by Dominant Pollutant (2023)
| Pollutant | Days as Dominant | Share of Year |
|---|---|---|
| Fine Particulate Matter (PM2.5) | 203 | 56% |
| Ground-Level Ozone | 150 | 41% |
| Coarse Particulate Matter (PM10) | 7 | 2% |
| Nitrogen Dioxide | 5 | 1% |
Is the Air Getting Better or Worse?
Air quality in Los Angeles, California has been improving over the past decade, with median AQI dropping by roughly 0.9 points per year. That is consistent with the broader national pattern — most U.S. metros have seen steady reductions in particulate and ozone pollution since the 2010s as cleaner vehicles and power plants come online.
In 2014, Los Angeles, California posted a median AQI of 82. By 2023 that figure was 67 — a drop of 15 AQI points cleaner across 10 years of EPA records.
Year-by-Year AQI in Los Angeles, California
| Year | Median AQI | Good Days | Unhealthy Days | Dominant Pollutant |
|---|---|---|---|---|
| 2014 | 82 | 8 | 107 | PM2.5 |
| 2015 | 80 | 3 | 132 | PM2.5 |
| 2016 | 77 | 7 | 104 | PM2.5 |
| 2017 | 79 | 9 | 119 | PM2.5 |
| 2018 | 78 | 7 | 108 | PM2.5 |
| 2019 | 72 | 34 | 86 | PM2.5 |
| 2020 | 85 | 35 | 137 | Ozone |
| 2021 | 79 | 9 | 97 | PM2.5 |
| 2022 | 74 | 17 | 94 | Ozone |
| 2023 | 67 | 41 | 87 | PM2.5 |
Health Context for Los Angeles, California
Across the past five years, this area has logged 501 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 100 days per year, or roughly one in three days on the calendar. That count places this area in the worst tier nationally and is the dominant driver of the D grade.
Treat daily AQI forecasts as essential input. On flagged days, sensitive groups (asthma, COPD, heart disease, pregnancy, young children, older adults) should limit outdoor exertion and keep windows closed. A HEPA air cleaner sized to a bedroom or family room can cut indoor PM2.5 by 80%+ during smoke or pollution events. Because PM2.5 penetrates deep into the lungs and bloodstream, an N95 or KN95 mask provides meaningful protection on smoky or high-particulate days — surgical masks do not.
How This Grade Is Calculated
The AirHistory Air Quality Grade combines four signals: the 5-year median AQI (40% of the score), the 10-year trend direction (30%), the count of unhealthy days per year (20%), and the dominant pollutant type (10%). All four come directly from the EPA Air Quality System (AQS), which aggregates readings from federally certified monitors. Read the full methodology.
Los Angeles, California has an Air Quality Grade of D (poor) with a 5-year median AQI of 75. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been improving over the past decade.
The data source behind this answer is the EPA Air Quality System (AQS). Every figure on the page traces back to that source; the methodology page describes the inputs and the refresh cadence in full detail.
For readers turning this answer into action: cross-reference against the underlying the EPA Air Quality System (AQS) record before acting on time-sensitive decisions. The site renders the data as it was published; subsequent revisions can shift the picture, and the live federal data is always the authoritative current reference.
Source: EPA Outdoor Air Quality Data, 2026.