Is the Air Quality Good in San Juan, Puerto Rico?
Yes — air quality in San Juan, Puerto Rico is good. The city earns an Air Quality Grade of A (excellent) on a 5-year median AQI of 10, which sits in the Good range, and logs only 0 unhealthy-air days over five years (about 0 per year). The general population can breathe outdoors safely on the vast majority of days.
Who Can Safely Breathe the Air in San Juan, Puerto Rico?
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. Day-to-day exposure can vary significantly within a single metro — sign up for AirNow.gov alerts at your specific zip code rather than relying on the city-level number.
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.
San Juan, Puerto Rico Air Quality Snapshot
| Air Quality Grade | A92/100 |
| 5-Year Median AQI | 10 (Good) |
| Most Recent Median AQI (2021) | 7 (Good) |
| Dominant Pollutant | Carbon Monoxide |
| 10-Year Trend | Improving (-1.07 AQI/yr) |
| Unhealthy Days (last 5 yr) | 0 |
| National Rank (cleanest = #1) | #12 of 1,020 (1th cleanest percentile) |
| Puerto Rico Rank | #3 of 11 |
What Does the A Grade Mean?
San Juan, Puerto Rico earns an A — it is among the cleanest U.S. cities tracked by EPA monitoring, with median AQI averaging just 10 over the past five years. Days in the "Good" category dominate the calendar; air-quality alerts are rare.
San Juan, Puerto Rico's 5-year median AQI of 10 is 31 points below the national average of 41 — meaningfully cleaner than the typical U.S. metro tracked here. Within Puerto Rico, San Juan, 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 San Juan, Puerto Rico's Air?
The dominant pollutant in San Juan, Puerto Rico is Carbon Monoxide. Carbon monoxide is a colorless, odorless gas produced by incomplete combustion — primarily older vehicles, fuel-burning appliances, and industrial sources. Outdoor CO has dropped dramatically since the 1980s thanks to catalytic converters; elevated readings today usually point to localized traffic congestion or a specific industrial source.
Days by Dominant Pollutant (2021)
| Pollutant | Days as Dominant | Share of Year |
|---|---|---|
| Carbon Monoxide | 41 | 100% |
Is the Air Getting Better or Worse?
Air quality in San Juan, Puerto Rico has been improving over the past decade, with median AQI dropping by roughly 1.1 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, San Juan, Puerto Rico posted a median AQI of 17. By 2021 that figure was 7 — a drop of 10 AQI points cleaner across 7 years of EPA records.
Year-by-Year AQI in San Juan, Puerto Rico
| Year | Median AQI | Good Days | Unhealthy Days | Dominant Pollutant |
|---|---|---|---|---|
| 2014 | 17 | 358 | 0 | CO |
| 2015 | 13 | 321 | 0 | CO |
| 2016 | 15 | 327 | 0 | CO |
| 2017 | 8 | 246 | 0 | CO |
| 2019 | 14 | 277 | 0 | CO |
| 2020 | 9 | 216 | 0 | CO |
| 2021 | 7 | 41 | 0 | CO |
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.
More about San Juan, Puerto Rico
San Juan, Puerto Rico has an Air Quality Grade of A (excellent) with a 5-year median AQI of 10. The dominant pollutant is Carbon Monoxide, and air quality has been improving over the past decade.
This answer pulls from the EPA Air Quality System (AQS), the authoritative federal source for U.S. air quality and pollution monitoring. The headline number above is the direct answer; what follows is the additional context most readers need to use the answer for a real decision rather than just a fact lookup.
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.