Median AQI
77
Moderate
California · County air quality · 2025
Los Angeles County, California
Median AQI 77 (Moderate). 10.9% of monitored days rated Good, direct from EPA Air Quality System stations.
- 77
- Median AQI
- 10.9%
- Good-air days
- 30
- Unhealthy days
- 0%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Los Angeles County's air is moderate on balance, among the most polluted counties nationally, a median AQI of 77 with 10.9% of 274 monitored days in the Good band, driven mainly by Ozone.
- 77
- median AQI · Moderate
- 10.9%
- days rated Good
- Ozone
- main pollutant
- 0%
- cleaner than US counties
30 days reached Unhealthy or worse; the worst single reading hit AQI 201.
Data updated July 2026
- Good · 30 d · 10.9%
- Moderate · 155 d · 56.6%
- USG · 59 d · 21.5%
- Unhealthy · 29 d · 10.6%
- Very Unhealthy · 1 d · 0.4%
How did Los Angeles County's air break down in 2025?
Across 274 monitored days, 30 fell in the Good band (AQI 0–50) and 30 reached Unhealthy or worse. The worst single day peaked at AQI 201 (Very Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 274 days monitored. Median AQI: 77 (Moderate).
Insights: Los Angeles County, California. EPA monitors recorded a median Air Quality Index of 77 across 274 measured days in 2025, earning a Moderate classification and a Very Poor health grade. Of those days, 30 (11%) fell in the Good band (AQI 0–50), 155 (57%) registered Moderate readings, and 59 (22%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 151, while the worst single-day peak hit 201 (Very Unhealthy). Residents averaged about 3.3 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (172 days), PM2.5 (87 days), PM10 (11 days), NO2 (3 days), CO (1 days). Across the 2020–2025 trend window, good days shifted by -5 and the median AQI moved -8 points, placing the multi-year trajectory at improving. Residents and visitors experienced 30 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Amador (84.8% good, AQI 40); Butte (66.1% good, AQI 47); Calaveras (73.9% good, AQI 43); Colusa (84.9% good, AQI 39); Del Norte (81.0% good, AQI 33); El Dorado (85.8% good, AQI 39).
Air Quality Summary
Good Days
10.9%
30 of 274 monitored days
-64.0pp vs 75% target
Max AQI Recorded
201
Very Unhealthy
Health Grade
Very Poor
90th-pct AQI 151
Los Angeles County, Good days share 10.9%
National avg
Share of monitored days at AQI 0-50 (Good band).
Los Angeles County, Unhealthy-or-worse share 10.9%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 274 monitored days across EPA AQI categories.
Good
30
11%
Moderate
155
57%
USG
59
22%
Unhealthy
29
11%
Very Unhealthy
1
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Los Angeles County.
- Ozone · 172 days · 62.8%
- PM2.5 · 87 days · 31.8%
- PM10 · 11 days · 4.0%
- NO₂ · 3 days · 1.1%
- CO · 1 days · 0.4%
Health Impact Assessment
Very Poor
Los Angeles County's air quality is rated Very Poor based on 10.9% good air days. There were 30 unhealthy days in 2025 when outdoor activity should be limited.
Air quality reached unhealthy levels on 30 days in 2025 (29 Unhealthy, 1 Very Unhealthy). Sensitive groups, including people with asthma, COPD, cardiovascular conditions, children, and adults over 65, should review the daily breakdown below and follow local air-quality advisories on high-AQI days.
Sensitive group advisory
People with asthma, COPD, heart disease, children, pregnant women, and adults 65+ should follow EPA AQI alerts daily and limit outdoor exertion when AQI exceeds 100. Real-time conditions: airnow.gov.
The dominant pollutant is Ozone, driving AQI on 172 of 274 monitored days.
5-Year Air Quality Trend
Air quality is improving in Los Angeles County. Best year: 2023 (41 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 35 | 194 | 77 | 43 | 85 | 250 |
| 2021 | 9 | 259 | 70 | 26 | 79 | 281 |
| 2022 | 17 | 254 | 65 | 28 | 74 | 209 |
| 2023 | 41 | 237 | 52 | 32 | 67 | 210 |
| 2024 | 38 | 195 | 78 | 46 | 80 | 230 |
| 2025 | 30 | 155 | 59 | 29 | 77 | 201 |
How does Los Angeles County compare?
How Los Angeles County compares
Good-day share worse than US avg
Los Angeles County 10.9%
Amador County, California 84.8%
US average 76.5%
Median AQI worse than US avg
Los Angeles County 77
Amador County, California 40
US average 38
Unhealthy days / yr worse than US avg
Los Angeles County 30
Amador County, California 0
US average 0
Other Counties in California
Air quality comparison for nearby counties in California.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Los Angeles County.
El Paso County, Texas
AQI 74 · 12.7% good
Maricopa County, Arizona
AQI 71 · 16.4% good
Dona Ana County, New Mexico
AQI 70 · 19.4% good
Riverside County, California
AQI 87 · 10.6% good
Pinal County, Arizona
AQI 66 · 24.6% good
Clark County, Nevada
AQI 64 · 25.6% good
What Los Angeles County's air means for you
On most days the air here is fine, but Ozone drives 30 unhealthy-or-worse days a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 77 means for exposure. Health guidance
- See how Los Angeles County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Los Angeles County with its California neighbours before drawing a conclusion about the region. All of California
Based on 274 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Los Angeles County, California? ▼
Los Angeles County has a median Air Quality Index (AQI) of 77, rated "Moderate." 10.9% of monitored days (30 out of 274) had good air quality in 2025.
What is the main pollutant in Los Angeles County? ▼
The primary pollutant in Los Angeles County is Ozone (O3), which was the main AQI driver on 172 days (63% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Los Angeles County have? ▼
In 2025, Los Angeles County recorded 30 unhealthy air days (29 Unhealthy, 1 Very Unhealthy, 0 Hazardous). The maximum AQI reached 201.
Is the air quality in Los Angeles County getting better or worse? ▼
Air quality in Los Angeles County is improving based on 5-year trends (2020-2025). Best year: 2023 with 41 good days. Worst year: 2021 with 9 good days.
What does AQI 77 mean for health? ▼
Los Angeles County's median AQI of 77 falls in the "Moderate" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Los Angeles County compare to other counties in California? ▼
Los Angeles County has 10.9% good air days. Nearby counties in California: Amador (84.8% good), Butte (66.1% good), Calaveras (73.9% good), Colusa (84.9% good), Del Norte (81.0% good), El Dorado (85.8% good).
What is the 90th percentile AQI in Los Angeles County? ▼
The 90th percentile AQI for Los Angeles County is 151, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 201 (Very Unhealthy).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.