Guaynabo, Puerto Rico Air Quality Today
AirHistory tracks long-run EPA monitoring rather than live readings, so for the live number check AirNow.gov below. As a baseline, Guaynabo, Puerto Rico's most recent EPA year (2023) posted a median AQI of 32 (Good) against a 5-year median of 29 and an overall Grade of C. The dominant pollutant is Nitrogen Dioxide, which tells you which days are most likely to spike.
Check Today's Live AQI in Guaynabo, Puerto Rico
AirHistory is built on 10 years of EPA Air Quality System records, so it shows you what air quality in Guaynabo, Puerto Rico typically looks like — not the live reading for this exact hour. For today's real-time AQI, check AirNow.gov (the EPA's official live index) or the AirNow Fire and Smoke Map during wildfire season.
That said, the history is the best predictor of a normal day. In 2023, Guaynabo, Puerto Rico posted a median AQI of 32 (Good), with 82 "Good" days and 0 days that crossed into "Unhealthy for Sensitive Groups" or worse. The dominant pollutant, Nitrogen Dioxide, is the one most likely to push today's number up — Nitrogen dioxide is emitted directly from vehicle engines, power plants, and gas appliances. It is highest near busy roads and in urban centers. Long-term NO2 exposure is linked to the development of asthma in children and to higher rates of respiratory infection.
Guaynabo, Puerto Rico Air Quality Snapshot
| Air Quality Grade | C62/100 |
| 5-Year Median AQI | 29 (Good) |
| Most Recent Median AQI (2023) | 32 (Good) |
| Dominant Pollutant | Nitrogen Dioxide |
| 10-Year Trend | Worsening (+1.44 AQI/yr) |
| Unhealthy Days (last 5 yr) | 4 |
| National Rank (cleanest = #1) | #123 of 1,020 (12th cleanest percentile) |
| Puerto Rico Rank | #9 of 11 |
What Does the C Grade Mean?
Guaynabo, Puerto Rico earns a C — air quality is fair, but not great. With a 5-year median AQI of 29, the city sees a meaningful number of "Moderate" days each year, when the EPA flags air as a concern for unusually sensitive people.
Guaynabo, Puerto Rico's 5-year median AQI of 29 is 12 points below the national average of 41 — meaningfully cleaner than the typical U.S. metro tracked here. Within Puerto Rico, Guaynabo, Puerto Rico runs more polluted than the state average of 23 — local sources or geography are concentrating pollution above the state's typical reading.
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 Guaynabo, Puerto Rico's Air?
The dominant pollutant in Guaynabo, Puerto Rico is Nitrogen Dioxide. Nitrogen dioxide is emitted directly from vehicle engines, power plants, and gas appliances. It is highest near busy roads and in urban centers. Long-term NO2 exposure is linked to the development of asthma in children and to higher rates of respiratory infection.
Days by Dominant Pollutant (2023)
| Pollutant | Days as Dominant | Share of Year |
|---|---|---|
| Fine Particulate Matter (PM2.5) | 102 | 95% |
| Coarse Particulate Matter (PM10) | 5 | 5% |
Is the Air Getting Better or Worse?
Air quality in Guaynabo, Puerto Rico has been getting worse over the past decade, with median AQI climbing by roughly 1.4 points per year. That bucks the national trend of broad improvement, and most often reflects either growing wildfire smoke exposure (particularly across the West) or rising local emissions from population and freight growth.
In 2014, Guaynabo, Puerto Rico posted a median AQI of 25. By 2023 that figure was 32 — a rise of 7 AQI points dirtier across 10 years of EPA records.
Year-by-Year AQI in Guaynabo, Puerto Rico
| Year | Median AQI | Good Days | Unhealthy Days | Dominant Pollutant |
|---|---|---|---|---|
| 2014 | 25 | 295 | 1 | PM10 |
| 2015 | 27 | 298 | 0 | PM10 |
| 2016 | 14 | 328 | 1 | NO2 |
| 2017 | 11 | 232 | 1 | NO2 |
| 2018 | 10 | 281 | 3 | NO2 |
| 2019 | 22 | 312 | 4 | NO2 |
| 2020 | 29 | 68 | 0 | PM2.5 |
| 2021 | 33 | 86 | 0 | PM2.5 |
| 2022 | 29 | 81 | 0 | PM2.5 |
| 2023 | 32 | 82 | 0 | PM2.5 |
Health Context for Guaynabo, Puerto Rico
Across the past five years, this area has logged just 4 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 1 days per year, or roughly one every other month. That is a low count by national standards.
Healthy adults can continue normal outdoor activity in most weather, but should pay attention to AQI alerts during the worst pollution windows. People with asthma, heart disease, or pregnancy should reduce prolonged or intense outdoor exertion on flagged days, and consider running an indoor HEPA air cleaner during peak season. NO2 concentrations drop quickly as you move away from traffic. Walking or biking on residential streets rather than along major arterials can cut personal exposure in half.
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 Guaynabo, Puerto Rico
Guaynabo, Puerto Rico has an Air Quality Grade of C (fair) with a 5-year median AQI of 29. The dominant pollutant is Nitrogen Dioxide, and air quality has been worsening 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.
A practical caveat: the headline answer above reflects the most recent the EPA Air Quality System (AQS) vintage; underlying data is often revised for months after first publication, and the right reference for any specific decision is whichever vintage is current at the time of the decision. The as-of date is stamped on every page.
Source: EPA Outdoor Air Quality Data, 2026.