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Annual Air Quality
Los Angeles County

Air Quality Days by Year, 1980-2024

Downtown Los Angeles Skyline as Seen From First AME Church, 2019

Downtown Los Angeles skyline looking northeast. Los Angeles Almanac Photo.


As bad a reputation as Los Angeles County has had with air pollution (not undeserved in light of its history), it ranked in 2023 behind two dozen other U.S. counties that had a higher number of unhealthy air quality days. These included Bannock County in Idaho, Riverside and San Bernardino Counties in California, and Uintah and Duchesne Counties in Utah.


The Air Quality Index Summary Report displays an annual summary of Air Quality Index (AQI) values for all U.S. counties. The AQI is an indicator of overall air quality, taking into account all criteria air pollutants (such as ozone, NO2, PM2.5 and PM10) measured within the county. Although the AQI includes all available pollutant measurements, each of the 11 monitoring stations in Los Angeles County (located in Azusa, Compton, Glendora, Lancaster, LAX, Long Beach, Downtown Los Angeles, Pasadena, Reseda and Santa Clarita), as in all counties, measure some, but not all, of the pollutants.


COLUMN DESCRIPTIONS FOR TABLE BELOW:

Good Quality Air Days - Number of days in the year when the Air Quality Index (AQI) value is 0 through 50. Air quality is considered satisfactory, and air pollution poses little or no risk.
Moderate Quality Air Days - Number of days in the year when the Air Quality Index (AQI) value is 51 through 100. Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.
Unhealthy Air for Sensitive Groups - Number of days in the year when the Air Quality Index (AQI) value is 100 through 150. Members of sensitive groups may experience health effects. The general public is not likely to be affected.
Unhealthy Air Days - Number of days in the year when the Air Quality Index (AQI) value is 151 through 150. Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.
Very Unhealthy or Hazardous Air Days - Number of days in the year when the Air Quality Index (AQI) value is 201 or higher. A health alert is issued for the day. Everyone may experience more serious health effects. When the AQI exceeds 300, the air situation is considered hazardous, meriting a health emergency. The entire population is more likely to be affected.


All years were measured over 365 days, except Leap Years (marked with obelus "†"), measured over 366 days.

Year Good Quality Air Days Moderate Quality Air Days Unhealthy Air for Sensitive Groups Unhealthy Air Days Very Unhealthy or Hazardous Air Days Total Unhealthy/ Hazardous Air Days
2024†* 38 199 76 44 9 129
2023 41 237 52 32 3 87
2022 17 254 65 28 1 94
2021 9 259 70 26 1 97
2020† 35 194 77 43 17 137
Year Good Quality Air Days Moderate Quality Air Days Unhealthy Air for Sensitive Groups Very Unhealthy or Hazardous Air Days Very Unhealthy Air Days Total Unhealthy/ Hazardous Air Days
2019 34 245 57 28 1 86
2018 7 250 89 18 1 108
2017 9 237 73 38 8 119
2016† 7 255 81 19 4 104
2015 3 230 95 36 1 132
Year Good Quality Air Days Moderate Quality Air Days Unhealthy Air for Sensitive Groups Unhealthy Air Days Very Unhealthy or Hazardous Air Days Total Unhealthy/ Hazardous Air Days
2014 8 250 79 26 2 107
2013 8 257 75 25 0 100
2012† 14 222 93 35 2 130
2011 2 242 82 36 3 121
2010 14 237 99 15 0 114
Year Good Quality Air Days Moderate Quality Air Days Unhealthy Air for Sensitive Groups Unhealthy Air Days Very Unhealthy or Hazardous Air Days Total Unhealthy/ Hazardous Air Days
2009 19 228 71 43 4 118
2008† 12 233 67 46 8 121
2007 24 214 91 30 6 127
2006 32 204 79 39 11 129
2005 36 191 77 48 13 138
Year Good Quality Air Days Moderate Quality Air Days Unhealthy Air for Sensitive Groups Unhealthy Air Days Very Unhealthy or Hazardous Air Days Total Unhealthy/ Hazardous Air Days
2004† 15 193 87 67 4 158
2003 22 173 83 57 30 170
2002 22 164 104 53 22 179
2001 13 166 127 48 11 186
2000† 15 176 114 51 10 175
Year Good Quality Air Days Moderate Quality Air Days Unhealthy Air for Sensitive Groups Unhealthy Air Days Very Unhealthy or Hazardous Air Days Total Unhealthy/ Hazardous Air Days
1999 17 180 140 27 1 168
1998 54 193 72 22 24 118
1997 33 171 116 32 13 161
1996† 42 154 91 47 32 170
1995 44 107 109 45 60 214
Year Good Quality Air Days Moderate Quality Air Days Unhealthy Air for Sensitive Groups Unhealthy Air Days Very Unhealthy or Hazardous Air Days Total Unhealthy/ Hazardous Air Days
1994 22 124 96 41 82 219
1993 29 108 111 45 72 228
1992† 22 104 92 59 89 240
1991 16 118 95 51 85 231
1990 17 119 84 56 89 229
Year Good Quality Air Days Moderate Quality Air Days Unhealthy Air for Sensitive Groups Unhealthy Air Days Very Unhealthy or Hazardous Air Days Total Unhealthy/ Hazardous Air Days
1989 10 69 110 63 113 286
1988† 9 65 84 63 145 292
1987 6 92 86 52 129 267
1986 7 72 92 54 140 286
1985 10 82 91 43 139 273
Year Good Quality Air Days Moderate Quality Air Days Unhealthy Air for Sensitive Groups Unhealthy Air Days Very Unhealthy or Hazardous Air Days Total Unhealthy/ Hazardous Air Days
1984† 5 71 101 52 137 290
1983 11 103 79 37 135 251
1982 8 83 91 54 129 274
1981 4 56 99 46 160 305
1980† 6 73 81 47 159 287

* Annual statistics for this year not finalized until May 1, 2025.
† Leap year with 366 days.

Source: Air Quality Reports, U.S. Environmental Protection Agency