Median AQI
74
Moderate
California · County air quality · 2025
Los Angeles County, California
Median AQI 74 (Moderate). 10.7% of monitored days rated Good, direct from EPA Air Quality System stations.
- 74
- Median AQI
- 10.7%
- Good-air days
- 32
- Unhealthy days
- 0%
- Cleaner than US counties
Los Angeles County's 2025 annual median AQI is 74 (Moderate), with 10.7% Good days
According to the U.S. EPA Air Quality System, Los Angeles County, California posted a 2025 median AQI of 74 (Moderate) across 365 monitored days, with 10.7% rated Good and 32 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Los Angeles County's 10.7% Good-day share places it cleaner than 0% of US counties in 2025.
- Closest median-AQI peer
- Maricopa County (8.8% Good, median AQI 73) is the closest nationwide median-AQI peer to Los Angeles County.
- 2020–2025 trend
- Los Angeles County's floor-qualifying Good-day share is improving from 2020 to 2025 (10.0% → 10.7%).
- Median AQI
- Median AQI: 74
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 74 with 10.7% of 365 monitored days in the Good band, driven mainly by Ozone.
- 74
- median AQI · Moderate
- 10.7%
- days rated Good
- Ozone
- main pollutant
- 0%
- cleaner than US counties
32 days reached Unhealthy or worse; the worst single reading hit AQI 201.
Annual release change
What changed in the 2025 EPA annual release
- Los Angeles County's Unhealthy-category days fell from 46 to 31 between the 2024 and 2025 EPA annual releases, a change of -15 days.
- Los Angeles County's peak single-day AQI fell from 230 to 201 between the 2024 and 2025 EPA annual releases, a change of -29 points.
- Los Angeles County's median AQI fell from 80 to 74 between the 2024 and 2025 EPA annual releases, a change of -6 points.
Data updated August 2026
- Good · 39 d · 10.7%
- Moderate · 228 d · 62.5%
- USG · 66 d · 18.1%
- Unhealthy · 31 d · 8.5%
- Very Unhealthy · 1 d · 0.3%
How did Los Angeles County's air break down in 2025?
Across 365 monitored days, 39 fell in the Good band (AQI 0–50) and 32 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). 365 days monitored. Median AQI: 74 (Moderate).
Insights: Los Angeles County, California. EPA monitors recorded a median Air Quality Index of 74 across 365 measured days in 2025, earning a Moderate classification and a Very Poor health grade. Of those days, 39 (11%) fell in the Good band (AQI 0–50), 228 (62%) registered Moderate readings, and 66 (18%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 147, while the worst single-day peak hit 201 (Very Unhealthy). Residents averaged about 3.2 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (193 days), PM2.5 (151 days), PM10 (15 days), NO2 (6 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by +1.1 points and the median AQI moved -11 points, placing the multi-year trajectory at improving. The annual record contains 32 days at Unhealthy or worse. On those days, the EPA recommends that sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Alameda (53.0% good, AQI 49); Amador (87.4% good, AQI 38); Butte (65.2% good, AQI 46); Calaveras (82.2% good, AQI 40); Colusa (79.2% good, AQI 40); Contra Costa (53.5% good, AQI 48).
Air Quality Summary
Good Days
10.7%
39 of 365 monitored days
-64.3pp vs 75% target
Max AQI Recorded
201
Very Unhealthy
Health Grade
Very Poor
90th-pct AQI 147
Los Angeles County, Good days share 10.7%
National avg
Share of monitored days at AQI 0-50 (Good band).
Los Angeles County, Unhealthy-or-worse share 87.7%
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 365 monitored days across EPA AQI categories.
Good
39
11%
Moderate
228
62%
USG
66
18%
Unhealthy
31
8%
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 · 193 days · 52.9%
- PM2.5 · 151 days · 41.4%
- PM10 · 15 days · 4.1%
- NO₂ · 6 days · 1.6%
Health Impact Assessment
Very Poor
Los Angeles County's air quality is rated Very Poor based on 10.7% good air days. There were 32 unhealthy days in 2025 when outdoor activity should be limited.
Air quality reached unhealthy levels on 32 days in 2025 (31 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 193 of 365 monitored days.
5-Year Air Quality Trend
Air quality is improving in Los Angeles County. Highest Good-day share: 2023 (11.3%, 41 of 365 monitored 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 | 39 | 228 | 66 | 31 | 74 | 201 |
How does Los Angeles County compare?
How Los Angeles County compares
Good-day share worse than typical
Los Angeles County 10.7%
Maricopa County, Arizona 8.8%
Typical US county 76.0%
Median AQI worse than typical
Los Angeles County 74
Maricopa County, Arizona 73
Typical US county 39
Unhealthy days / yr worse than typical
Los Angeles County 32
Maricopa County, Arizona 6
Typical US county 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Los Angeles County (74), not geographic neighbors.
Maricopa County, Arizona
Median AQI 73 · 8.8% Good-day share
San Bernardino County, California
Median AQI 77 · 12.6% Good-day share
El Paso County, Texas
Median AQI 70 · 18.1% Good-day share
Kern County, California
Median AQI 70 · 17.5% Good-day share
Riverside County, California
Median AQI 80 · 10.7% Good-day share
Pinal County, Arizona
Median AQI 67 · 17.0% Good-day share
Same primary pollutant: Ozone
Ozone led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Tulare County, California
24.1% Good-day share · median AQI 64
Bernalillo County, New Mexico
26.6% Good-day share · median AQI 58
Dona Ana County, New Mexico
27.4% Good-day share · median AQI 61
Imperial County, California
27.7% Good-day share · median AQI 64
Fresno County, California
28.8% Good-day share · median AQI 61
Clark County, Nevada
31.0% Good-day share · median AQI 61
California counties on the map
Geographic containment only, other monitored counties in California, independent of AQI or pollutant match.
What Los Angeles County's air means for you
On most days the air here is fine, but Ozone drives 32 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 74 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 365 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
Frequently Asked Questions
What is the air quality in Los Angeles County, California? ▼
Los Angeles County has a median Air Quality Index (AQI) of 74, rated "Moderate." 10.7% of monitored days (39 out of 365) 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 193 days (53% 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 32 unhealthy air days (31 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 across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2023 at 11.3% (41 of 365 days). Lowest qualifying Good-day share: 2021 at 2.5% (9 of 365 days).
What does AQI 74 mean for health? ▼
Los Angeles County's median AQI of 74 falls in the "Moderate" category. See the AQI category guide for what each range means for health.
How does Los Angeles County compare to other counties in California? ▼
Los Angeles County has 10.7% good air days. Nearby counties in California: Alameda (53.0% good), Amador (87.4% good), Butte (65.2% good), Calaveras (82.2% good), Colusa (79.2% good), Contra Costa (53.5% good).
What is the 90th percentile AQI in Los Angeles County? ▼
The 90th percentile AQI for Los Angeles County is 147, 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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Los Angeles County, California · 2020–2025
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Every figure on PlainAirData 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.