Daily Air Quality Index summaries from EPA monitors in Guaynabo, Puerto Rico, 1985–2025.
86%
Good days in 2019
22
Median daily AQI, 2019
4
Days above 100 in 2019
362
Days with an AQI in 2019 (of 365)
In 2019, EPA reported a daily Air Quality Index (AQI) for Guaynabo, Puerto Rico on 362 days. 312 of those days (86%) were in the Good range, and the median daily AQI was 22. That median is about the same as the typical monitored county in Puerto Rico (median 22 across 7 counties), and lower than the typical monitored U.S. county (41). The main pollutant was nitrogen dioxide (NO₂) on 223 days. Across the years with fuller monitoring, the share of Good days rose: an average of 88% in 1991–1993 versus 91% in 2017–2019.
Years with fewer than 120 monitored days (2020, 2021, 2022, 2023, 2024, 2025…) 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.
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 daily AQI
90th-percentile daily AQI
Main pollutant by day, 2019
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.
Pollutant
Days as main pollutant
Share of monitored days
Nitrogen dioxide (NO₂)
223
62%
Fine particles (PM2.5)
112
31%
Carbon monoxide (CO)
23
6%
Coarse particles (PM10)
4
1%
Year-by-year data
Annual AQI summary by year
Year
Days with AQI
Good
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very Unhealthy
Hazardous
Median AQI
90th pct.
Max AQI
Main pollutant
2025
114
93
21
0
0
0
0
33
57
67
PM2.5
2024
115
91
24
0
0
0
0
31
56
81
PM2.5
2023
107
82
25
0
0
0
0
32
59
74
PM2.5
2022
94
81
13
0
0
0
0
29
55
80
PM2.5
2021
119
86
33
0
0
0
0
33
64
77
PM2.5
2020
83
68
15
0
0
0
0
29
59
75
PM2.5
2019
362
312
46
4
0
0
0
22
56
110
NO2
2018
302
281
18
2
1
0
0
10
44
176
NO2
2017
248
232
15
0
1
0
0
11
40
151
NO2
2016
365
328
36
1
0
0
0
14
51
119
NO2
2015
353
298
55
0
0
0
0
27
57
100
PM10
2014
329
295
33
0
0
1
0
25
51
253
PM10
2013
331
292
39
0
0
0
0
29
51
68
PM10
2012
330
273
57
0
0
0
0
30
56
83
PM10
2011
336
305
31
0
0
0
0
26
48
65
PM10
2010
347
315
32
0
0
0
0
26
48
100
PM10
2009
184
161
23
0
0
0
0
28
52
93
PM10
2008
310
268
42
0
0
0
0
34
52
81
PM2.5
2007
355
261
93
1
0
0
0
38
57
119
PM2.5
2006
355
241
114
0
0
0
0
42
57
90
PM2.5
2005
362
246
116
0
0
0
0
43
61
89
PM2.5
2004
358
267
91
0
0
0
0
40
57
99
PM2.5
2003
360
213
147
0
0
0
0
47
59
82
PM2.5
2002
359
182
177
0
0
0
0
50
62
81
PM2.5
2001
355
149
204
2
0
0
0
52
64
122
PM2.5
2000
340
198
142
0
0
0
0
48
61
77
PM2.5
1999
349
175
174
0
0
0
0
50
62
78
PM2.5
1998
340
299
40
1
0
0
0
30
52
107
PM10
1997
363
309
52
2
0
0
0
31
57
111
PM10
1996
357
327
29
1
0
0
0
29
48
107
PM10
1995
358
341
17
0
0
0
0
27
41
85
PM10
1994
364
320
44
0
0
0
0
30
52
70
PM10
1993
365
306
59
0
0
0
0
31
57
73
PM10
1992
364
330
34
0
0
0
0
27
50
75
PM10
1991
307
273
34
0
0
0
0
31
51
90
PM10
1990
54
37
17
0
0
0
0
40
60
76
PM10
1989
36
30
6
0
0
0
0
35
60
75
PM10
1988
54
44
10
0
0
0
0
42
64
96
PM10
1987
46
36
9
0
1
0
0
35
57
166
PM10
1986
50
46
4
0
0
0
0
30
50
62
PM10
1985
27
17
10
0
0
0
0
42
68
90
PM10
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.
