EnviroNearby

Bayamon, Puerto Rico air quality history

Daily Air Quality Index summaries from EPA monitors in Bayamon, Puerto Rico, 1987–2025.

86%
Good days in 2025
29
Median daily AQI, 2025
2
Days above 100 in 2025
164
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Bayamon, Puerto Rico on 164 days. 141 of those days (86%) were in the Good range, and the median daily AQI was 29. That median is higher than the typical monitored county in Puerto Rico (median 9 across 5 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 164 days. Across the years with fuller monitoring, the share of Good days fell: an average of 100% in 2008–2010 versus 87% in 2023–2025.

EPA did not report an AQI for every day of 2025 here (164 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

Years with fewer than 120 monitored days (2002, 2003, 2004, 2005, 2006, 2007…) are shown in the table but left out of comparisons and trend statements.

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%1987: Good 1 of 1 days19871988: Good 33 of 36 days1988: Moderate 3 of 36 days1989: Good 46 of 51 days1989: Moderate 5 of 51 days1990: Good 52 of 58 days1990: Moderate 6 of 58 days1991: Good 50 of 54 days1991: Moderate 4 of 54 days1992: Good 52 of 57 days1992: Moderate 5 of 57 days19921993: Good 51 of 58 days1993: Moderate 7 of 58 days1994: Good 45 of 47 days1994: Moderate 2 of 47 days1995: Good 52 of 53 days1995: Moderate 1 of 53 days1996: Good 54 of 55 days1996: Moderate 1 of 55 days1997: Good 52 of 58 days1997: Moderate 6 of 58 days19971998: Good 57 of 59 days1998: Moderate 2 of 59 days1999: Good 79 of 103 days1999: Moderate 24 of 103 days2000: Good 91 of 112 days2000: Moderate 21 of 112 days2001: Good 98 of 118 days2001: Moderate 19 of 118 days2001: Unhealthy for Sensitive Groups 1 of 118 days2002: Good 98 of 115 days2002: Moderate 17 of 115 days20022003: Good 93 of 109 days2003: Moderate 16 of 109 days2004: Good 100 of 111 days2004: Moderate 11 of 111 days2005: Good 97 of 118 days2005: Moderate 21 of 118 days2006: Good 79 of 105 days2006: Moderate 26 of 105 days2007: Good 87 of 98 days2007: Moderate 11 of 98 days20072008: Good 240 of 240 days2009: Good 247 of 247 days2010: Good 324 of 325 days2010: Moderate 1 of 325 days2011: Good 222 of 223 days2011: Moderate 1 of 223 days2012: Good 291 of 315 days2012: Moderate 24 of 315 days20122013: Good 351 of 357 days2013: Moderate 5 of 357 days2013: Unhealthy for Sensitive Groups 1 of 357 days2014: Good 271 of 272 days2014: Moderate 1 of 272 days2015: Good 241 of 267 days2015: Moderate 25 of 267 days2015: Unhealthy for Sensitive Groups 1 of 267 days2016: Good 199 of 267 days2016: Moderate 66 of 267 days2016: Unhealthy for Sensitive Groups 1 of 267 days2016: Unhealthy 1 of 267 days2017: Good 46 of 159 days2017: Moderate 109 of 159 days2017: Unhealthy for Sensitive Groups 4 of 159 days20172018: Good 76 of 264 days2018: Moderate 175 of 264 days2018: Unhealthy for Sensitive Groups 7 of 264 days2018: Unhealthy 6 of 264 days2019: Good 239 of 278 days2019: Moderate 39 of 278 days2020: Good 259 of 270 days2020: Moderate 11 of 270 days2021: Good 320 of 347 days2021: Moderate 27 of 347 days2022: Good 342 of 358 days2022: Moderate 16 of 358 days20222023: Good 193 of 216 days2023: Moderate 23 of 216 days2024: Good 268 of 314 days2024: Moderate 45 of 314 days2024: Unhealthy for Sensitive Groups 1 of 314 days2025: Good 141 of 164 days2025: Moderate 21 of 164 days2025: Unhealthy for Sensitive Groups 2 of 164 days2025
  • 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 year0501001987: 90th percentile AQI 341988: 90th percentile AQI 451989: 90th percentile AQI 431990: 90th percentile AQI 541991: 90th percentile AQI 481992: 90th percentile AQI 461993: 90th percentile AQI 521994: 90th percentile AQI 401995: 90th percentile AQI 281996: 90th percentile AQI 281997: 90th percentile AQI 581998: 90th percentile AQI 441999: 90th percentile AQI 562000: 90th percentile AQI 542001: 90th percentile AQI 532002: 90th percentile AQI 522003: 90th percentile AQI 532004: 90th percentile AQI 482005: 90th percentile AQI 542006: 90th percentile AQI 542007: 90th percentile AQI 522008: 90th percentile AQI 232009: 90th percentile AQI 202010: 90th percentile AQI 162011: 90th percentile AQI 152012: 90th percentile AQI 432013: 90th percentile AQI 282014: 90th percentile AQI 222015: 90th percentile AQI 502016: 90th percentile AQI 532017: 90th percentile AQI 792018: 90th percentile AQI 832019: 90th percentile AQI 532020: 90th percentile AQI 382021: 90th percentile AQI 412022: 90th percentile AQI 332023: 90th percentile AQI 522024: 90th percentile AQI 542025: 90th percentile AQI 551987: Median AQI 341988: Median AQI 251989: Median AQI 221990: Median AQI 231991: Median AQI 221992: Median AQI 191993: Median AQI 221994: Median AQI 181995: Median AQI 151996: Median AQI 161997: Median AQI 251998: Median AQI 211999: Median AQI 342000: Median AQI 332001: Median AQI 332002: Median AQI 332003: Median AQI 292004: Median AQI 242005: Median AQI 292006: Median AQI 322007: Median AQI 302008: Median AQI 162009: Median AQI 162010: Median AQI 92011: Median AQI 62012: Median AQI 162013: Median AQI 92014: Median AQI 102015: Median AQI 182016: Median AQI 232017: Median AQI 602018: Median AQI 562019: Median AQI 202020: Median AQI 212021: Median AQI 102022: Median AQI 152023: Median AQI 222024: Median AQI 272025: Median AQI 29198719921997200220072012201720222025
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2025

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)164100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20251641412120002955102PM2.5
20243142684510002754124PM2.5
2023216193230000225274PM2.5
2022358342160000153377CO
2021347320270000104177CO
2020270259110000213869CO
2019278239390000205379PM2.5
20182647617576005683172PM2.5
20171594610940006079132PM2.5
20162671996611002353177Ozone
20152672412510001850146Ozone
201427227110000102251CO
201335735151000928106CO
2012315291240000164375CO
20112232221000061566CO
20103253241000091677CO
200924724700000162028CO
200824024000000162326CO
20079887110000305266PM2.5
200610579260000325477PM2.5
200511897210000295470PM2.5
2004111100110000244862PM2.5
200310993160000295378PM2.5
200211598170000335268PM2.5
2001118981910003353103PM2.5
200011291210000335488PM2.5
199910379240000345669PM2.5
1998595720000214474PM10
1997585260000255889PM10
1996555410000162889PM10
1995535210000152853PM10
1994474520000184064PM10
1993585170000225263PM10
1992575250000194667PM10
1991545040000224879PM10
1990585260000235456PM10
1989514650000224373PM10
1988363330000254577PM10
19871100000343434PM10

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 Puerto Rico with a similar median AQI in 2025

All monitored counties in Puerto Rico

Source: U.S. EPA AirData, “Annual AQI by County” files for 1987–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem