EnviroNearby

Alameda County, California air quality history

Daily Air Quality Index summaries from EPA monitors in Alameda, California, 1980–2024.

53%
Good days in 2024
49
Median daily AQI, 2024
1
Days above 100 in 2024
366
Days with an AQI in 2024 (of 366)

In 2024, EPA reported a daily Air Quality Index (AQI) for Alameda, California on 366 days. 194 of those days (53%) were in the Good range, and the median daily AQI was 49. That median is higher than the typical monitored county in California (median 46.5 across 52 counties), and higher than the typical monitored U.S. county (41). The main pollutant was fine particles (PM2.5) on 352 days. Across the years with fuller monitoring, the share of Good days fell: an average of 68% in 1980–1982 versus 53% in 2022–2024.

The most recent year with data for this county is 2024; EPA's files for 2025–2025 contain no row for it, which usually means its monitors stopped reporting.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Share of monitored days in each AQI category, by year0%25%50%75%100%1980: Good 237 of 366 days1980: Moderate 106 of 366 days1980: Unhealthy for Sensitive Groups 15 of 366 days1980: Unhealthy 4 of 366 days1980: Very Unhealthy 4 of 366 days19801981: Good 242 of 365 days1981: Moderate 95 of 365 days1981: Unhealthy for Sensitive Groups 23 of 365 days1981: Unhealthy 4 of 365 days1981: Very Unhealthy 1 of 365 days1982: Good 268 of 365 days1982: Moderate 82 of 365 days1982: Unhealthy for Sensitive Groups 12 of 365 days1982: Unhealthy 3 of 365 days1983: Good 276 of 365 days1983: Moderate 66 of 365 days1983: Unhealthy for Sensitive Groups 11 of 365 days1983: Unhealthy 8 of 365 days1983: Very Unhealthy 4 of 365 days1984: Good 254 of 366 days1984: Moderate 79 of 366 days1984: Unhealthy for Sensitive Groups 20 of 366 days1984: Unhealthy 10 of 366 days1984: Very Unhealthy 3 of 366 days1985: Good 226 of 365 days1985: Moderate 112 of 365 days1985: Unhealthy for Sensitive Groups 17 of 365 days1985: Unhealthy 9 of 365 days1985: Very Unhealthy 1 of 365 days19851986: Good 239 of 365 days1986: Moderate 93 of 365 days1986: Unhealthy for Sensitive Groups 28 of 365 days1986: Unhealthy 4 of 365 days1986: Very Unhealthy 1 of 365 days1987: Good 271 of 365 days1987: Moderate 70 of 365 days1987: Unhealthy for Sensitive Groups 14 of 365 days1987: Unhealthy 8 of 365 days1987: Very Unhealthy 2 of 365 days1988: Good 225 of 366 days1988: Moderate 106 of 366 days1988: Unhealthy for Sensitive Groups 27 of 366 days1988: Unhealthy 8 of 366 days1989: Good 237 of 365 days1989: Moderate 101 of 365 days1989: Unhealthy for Sensitive Groups 22 of 365 days1989: Unhealthy 5 of 365 days1990: Good 265 of 365 days1990: Moderate 87 of 365 days1990: Unhealthy for Sensitive Groups 9 of 365 days1990: Unhealthy 4 of 365 days19901991: Good 248 of 365 days1991: Moderate 96 of 365 days1991: Unhealthy for Sensitive Groups 19 of 365 days1991: Unhealthy 2 of 365 days1992: Good 280 of 366 days1992: Moderate 69 of 366 days1992: Unhealthy for Sensitive Groups 14 of 366 days1992: Unhealthy 3 of 366 days1993: Good 275 of 365 days1993: Moderate 78 of 365 days1993: Unhealthy for Sensitive Groups 8 of 365 days1993: Unhealthy 4 of 365 days1994: Good 289 of 365 days1994: Moderate 69 of 365 days1994: Unhealthy for Sensitive Groups 4 of 365 days1994: Unhealthy 3 of 365 days1995: Good 289 of 365 days1995: Moderate 54 of 365 days1995: Unhealthy for Sensitive Groups 10 of 365 days1995: Unhealthy 8 of 365 days1995: Very Unhealthy 4 of 365 days19951996: Good 280 of 366 days1996: Moderate 62 of 366 days1996: Unhealthy for Sensitive Groups 14 of 366 days1996: Unhealthy 9 of 366 days1996: Very Unhealthy 1 of 366 days1997: Good 324 of 365 days1997: Moderate 35 of 365 days1997: Unhealthy for Sensitive Groups 6 of 365 days1998: Good 306 of 365 days1998: Moderate 39 of 365 days1998: Unhealthy for Sensitive Groups 11 of 365 days1998: Unhealthy 8 of 365 days1998: Very Unhealthy 1 of 365 days1999: Good 248 of 365 days1999: Moderate 91 of 365 days1999: Unhealthy for Sensitive Groups 19 of 365 days1999: Unhealthy 5 of 365 days1999: Very Unhealthy 2 of 365 days2000: Good 272 of 366 days2000: Moderate 80 of 366 days2000: Unhealthy for Sensitive Groups 11 of 366 days2000: Unhealthy 2 of 366 days2000: Very Unhealthy 1 of 366 days20002001: Good 269 of 365 days2001: Moderate 78 of 365 days2001: Unhealthy for Sensitive Groups 12 of 365 days2001: Unhealthy 6 of 365 days2002: Good 256 of 365 days2002: Moderate 87 of 365 days2002: Unhealthy for Sensitive Groups 15 of 365 days2002: Unhealthy 6 of 365 days2002: Very Unhealthy 1 of 365 days2003: Good 278 of 365 days2003: Moderate 75 of 365 days2003: Unhealthy for Sensitive Groups 9 of 365 days2003: Unhealthy 3 of 365 days2004: Good 169 of 366 days2004: Moderate 181 of 366 days2004: Unhealthy for Sensitive Groups 16 of 366 days2005: Good 182 of 365 days2005: Moderate 169 of 365 days2005: Unhealthy for Sensitive Groups 12 of 365 days2005: Unhealthy 2 of 365 days20052006: Good 158 of 365 days2006: Moderate 185 of 365 days2006: Unhealthy for Sensitive Groups 17 of 365 days2006: Unhealthy 5 of 365 days2007: Good 245 of 365 days2007: Moderate 111 of 365 days2007: Unhealthy for Sensitive Groups 8 of 365 days2007: Unhealthy 1 of 365 days2008: Good 101 of 366 days2008: Moderate 249 of 366 days2008: Unhealthy for Sensitive Groups 12 of 366 days2008: Unhealthy 3 of 366 days2008: Very Unhealthy 1 of 366 days2009: Good 121 of 365 days2009: Moderate 231 of 365 days2009: Unhealthy for Sensitive Groups 12 of 365 days2009: Unhealthy 1 of 365 days2010: Good 161 of 365 days2010: Moderate 199 of 365 days2010: Unhealthy for Sensitive Groups 4 of 365 days2010: Unhealthy 1 of 365 days20102011: Good 145 of 365 days2011: Moderate 209 of 365 days2011: Unhealthy for Sensitive Groups 11 of 365 days2012: Good 186 of 366 days2012: Moderate 176 of 366 days2012: Unhealthy for Sensitive Groups 3 of 366 days2012: Unhealthy 1 of 366 days2013: Good 105 of 365 days2013: Moderate 252 of 365 days2013: Unhealthy for Sensitive Groups 8 of 365 days2014: Good 169 of 365 days2014: Moderate 186 of 365 days2014: Unhealthy for Sensitive Groups 10 of 365 days2015: Good 146 of 365 days2015: Moderate 207 of 365 days2015: Unhealthy for Sensitive Groups 12 of 365 days20152016: Good 155 of 366 days2016: Moderate 196 of 366 days2016: Unhealthy for Sensitive Groups 13 of 366 days2016: Unhealthy 2 of 366 days2017: Good 106 of 365 days2017: Moderate 245 of 365 days2017: Unhealthy for Sensitive Groups 9 of 365 days2017: Unhealthy 4 of 365 days2017: Very Unhealthy 1 of 365 days2018: Good 77 of 365 days2018: Moderate 271 of 365 days2018: Unhealthy for Sensitive Groups 5 of 365 days2018: Unhealthy 9 of 365 days2018: Very Unhealthy 3 of 365 days2019: Good 183 of 365 days2019: Moderate 174 of 365 days2019: Unhealthy for Sensitive Groups 8 of 365 days2020: Good 169 of 366 days2020: Moderate 177 of 366 days2020: Unhealthy for Sensitive Groups 8 of 366 days2020: Unhealthy 11 of 366 days2020: Very Unhealthy 1 of 366 days20202021: Good 155 of 365 days2021: Moderate 200 of 365 days2021: Unhealthy for Sensitive Groups 9 of 365 days2021: Unhealthy 1 of 365 days2022: Good 185 of 365 days2022: Moderate 175 of 365 days2022: Unhealthy for Sensitive Groups 5 of 365 days2023: Good 197 of 365 days2023: Moderate 155 of 365 days2023: Unhealthy for Sensitive Groups 13 of 365 days2024: Good 194 of 366 days2024: Moderate 171 of 366 days2024: Unhealthy for Sensitive Groups 1 of 366 days2024
  • Good
  • Moderate
  • Unhealthy for Sensitive Groups
  • Unhealthy
  • Very Unhealthy
  • Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median and 90th-percentile daily AQI, by year0501001980: 90th percentile AQI 891981: 90th percentile AQI 901982: 90th percentile AQI 791983: 90th percentile AQI 871984: 90th percentile AQI 1001985: 90th percentile AQI 901986: 90th percentile AQI 1001987: 90th percentile AQI 871988: 90th percentile AQI 1001989: 90th percentile AQI 891990: 90th percentile AQI 791991: 90th percentile AQI 891992: 90th percentile AQI 741993: 90th percentile AQI 711994: 90th percentile AQI 641995: 90th percentile AQI 681996: 90th percentile AQI 801997: 90th percentile AQI 531998: 90th percentile AQI 651999: 90th percentile AQI 872000: 90th percentile AQI 712001: 90th percentile AQI 722002: 90th percentile AQI 822003: 90th percentile AQI 682004: 90th percentile AQI 842005: 90th percentile AQI 782006: 90th percentile AQI 852007: 90th percentile AQI 712008: 90th percentile AQI 852009: 90th percentile AQI 812010: 90th percentile AQI 722011: 90th percentile AQI 772012: 90th percentile AQI 682013: 90th percentile AQI 812014: 90th percentile AQI 722015: 90th percentile AQI 792016: 90th percentile AQI 742017: 90th percentile AQI 782018: 90th percentile AQI 792019: 90th percentile AQI 672020: 90th percentile AQI 812021: 90th percentile AQI 712022: 90th percentile AQI 702023: 90th percentile AQI 702024: 90th percentile AQI 631980: Median AQI 401981: Median AQI 431982: Median AQI 391983: Median AQI 381984: Median AQI 421985: Median AQI 471986: Median AQI 441987: Median AQI 401988: Median AQI 471989: Median AQI 441990: Median AQI 381991: Median AQI 401992: Median AQI 381993: Median AQI 381994: Median AQI 391995: Median AQI 381996: Median AQI 401997: Median AQI 381998: Median AQI 381999: Median AQI 422000: Median AQI 412001: Median AQI 412002: Median AQI 422003: Median AQI 402004: Median AQI 522005: Median AQI 512006: Median AQI 532007: Median AQI 422008: Median AQI 562009: Median AQI 562010: Median AQI 522011: Median AQI 532012: Median AQI 502013: Median AQI 562014: Median AQI 522015: Median AQI 542016: Median AQI 522017: Median AQI 562018: Median AQI 572019: Median AQI 502020: Median AQI 522021: Median AQI 532022: Median AQI 492023: Median AQI 482024: Median AQI 491980198519901995200020052010201520202024
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2024

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

PollutantDays as main pollutantShare of monitored days
Fine particles (PM2.5)35296%
Ozone144%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202436619417110004963105PM2.5
2023365197155130004870130PM2.5
202236518517550004970122PM2.5
202136515520091005371151PM2.5
2020366169177811105281243PM2.5
201936518317480005067150PM2.5
20183657727159305779248PM2.5
201736510624594105678205PM2.5
2016366155196132005274154PM2.5
2015365146207120005479147PM2.5
2014365169186100005272133PM2.5
201336510525280005681122PM2.5
201236618617631005068161PM2.5
2011365145209110005377147PM2.5
201036516119941005272179PM2.5
2009365121231121005681151PM2.5
2008366101249123105685205PM2.5
200736524511181004271164PM2.5
2006365158185175005385190PM2.5
2005365182169122005178161PM2.5
2004366169181160005284136PM2.5
20033652787593004068172Ozone
200236525687156104282201Ozone
200136526978126004172187Ozone
200036627280112104171209Ozone
199936524891195204287212Ozone
199836530639118103865205Ozone
19973653243560003853147Ozone
199636628062149104080207Ozone
199536528954108403868210NO2
19943652896943003964166NO2
19933652757884003871192Ozone
199236628069143003874164Ozone
199136524896192004089166NO2
19903652658794003879200NO2
1989365237101225004489190Ozone
19883662251062780047100177NO2
198736527170148204087212NO2
1986365239932841044100201NO2
1985365226112179104790201NO2
19843662547920103042100214NO2
198336527666118403887223NO2
198236526882123003979179NO2
198136524295234104390205NO2
1980366237106154404089232NO2

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in California with a similar median AQI in 2024

All monitored counties in California

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–2024 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem