What Is the Air Quality in Adjuntas, Puerto Rico?
Adjuntas, Puerto Rico has an Air Quality Grade of A (excellent) with a 5-year median AQI of 19. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been improving over the past decade.
Adjuntas, Puerto Rico Air Quality Snapshot
| Air Quality Grade | A88/100 |
| 5-Year Median AQI | 19 (Good) |
| Most Recent Median AQI (2021) | 14 (Good) |
| Dominant Pollutant | Fine Particulate Matter (PM2.5) |
| 10-Year Trend | Improving (-1.73 AQI/yr) |
| Unhealthy Days (last 5 yr) | 0 |
| National Rank (cleanest = #1) | #55 of 1,020 (5th cleanest percentile) |
| Puerto Rico Rank | #5 of 11 |
What Does the A Grade Mean?
Adjuntas, Puerto Rico earns an A — it is among the cleanest U.S. cities tracked by EPA monitoring, with median AQI averaging just 19 over the past five years. Days in the "Good" category dominate the calendar; air-quality alerts are rare.
Adjuntas, Puerto Rico's 5-year median AQI of 19 is 22 points below the national average of 41 — meaningfully cleaner than the typical U.S. metro tracked here. Within Puerto Rico, Adjuntas, Puerto Rico runs cleaner than the state average of 23 — a positive signal that local conditions (terrain, wind patterns, emission sources) are working in residents' favor.
For context within Puerto Rico: Caguas, Puerto Rico currently holds the state's cleanest grade (A, AQI 10), while Catano, Puerto Rico sits at the bottom (D, AQI 42).
What's in Adjuntas, Puerto Rico's Air?
The dominant pollutant in Adjuntas, Puerto Rico is Fine Particulate Matter (PM2.5). Fine particulate matter — particles less than 2.5 micrometers across — comes mostly from combustion: vehicle exhaust, wildfire smoke, residential wood burning, and industrial emissions. Because these particles are small enough to enter the bloodstream, PM2.5 is the pollutant most strongly linked to cardiovascular disease, respiratory illness, and premature death.
Days by Dominant Pollutant (2021)
| Pollutant | Days as Dominant | Share of Year |
|---|---|---|
| Fine Particulate Matter (PM2.5) | 7 | 100% |
Is the Air Getting Better or Worse?
Air quality in Adjuntas, Puerto Rico has been improving over the past decade, with median AQI dropping by roughly 1.7 points per year. That is consistent with the broader national pattern — most U.S. metros have seen steady reductions in particulate and ozone pollution since the 2010s as cleaner vehicles and power plants come online.
In 2014, Adjuntas, Puerto Rico posted a median AQI of 24. By 2021 that figure was 14 — a drop of 10 AQI points cleaner across 8 years of EPA records.
Year-by-Year AQI in Adjuntas, Puerto Rico
| Year | Median AQI | Good Days | Unhealthy Days | Dominant Pollutant |
|---|---|---|---|---|
| 2014 | 24 | 36 | 0 | PM2.5 |
| 2015 | 27 | 80 | 0 | PM2.5 |
| 2016 | 28 | 85 | 0 | PM2.5 |
| 2017 | 37 | 35 | 0 | PM2.5 |
| 2018 | 19 | 27 | 0 | PM2.5 |
| 2019 | 24 | 98 | 0 | PM2.5 |
| 2020 | 18 | 52 | 0 | PM2.5 |
| 2021 | 14 | 7 | 0 | PM2.5 |
Health Context for Adjuntas, Puerto Rico
Across the past five years, this area has logged just 0 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 0 days per year, or roughly one every other month. That is a low count by national standards.
For most healthy adults, current air quality in this area does not require any change in behavior. People with severe asthma, COPD, or recent cardiac events should still keep an eye on daily AQI alerts, especially during wildfire season. Because PM2.5 penetrates deep into the lungs and bloodstream, an N95 or KN95 mask provides meaningful protection on smoky or high-particulate days — surgical masks do not.
How This Grade Is Calculated
The AirHistory Air Quality Grade combines four signals: the 5-year median AQI (40% of the score), the 10-year trend direction (30%), the count of unhealthy days per year (20%), and the dominant pollutant type (10%). All four come directly from the EPA Air Quality System (AQS), which aggregates readings from federally certified monitors. Read the full methodology.
Adjuntas, Puerto Rico has an Air Quality Grade of A (excellent) with a 5-year median AQI of 19. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been improving over the past decade.
The data source behind this answer is the EPA Air Quality System (AQS). Every figure on the page traces back to that source; the methodology page describes the inputs and the refresh cadence in full detail.
For readers turning this answer into action: cross-reference against the underlying the EPA Air Quality System (AQS) record before acting on time-sensitive decisions. The site renders the data as it was published; subsequent revisions can shift the picture, and the live federal data is always the authoritative current reference.
Source: EPA Outdoor Air Quality Data, 2026.