Daily Air Quality Index summaries from EPA monitors in Dukes, Massachusetts, 2003–2025.
96%
Good days in 2025
35
Median daily AQI, 2025
2
Days above 100 in 2025
341
Days with an AQI in 2025 (of 365)
In 2025, EPA reported a daily Air Quality Index (AQI) for Dukes, Massachusetts on 341 days. 327 of those days (96%) were in the Good range, and the median daily AQI was 35. That median is lower than the typical monitored county in Massachusetts (median 38 across 13 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 318 days. Across the years with fuller monitoring, the share of Good days rose: an average of 74% in 2004–2006 versus 93% in 2023–2025.
Years with fewer than 120 monitored days (2003) 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, 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.
Pollutant
Days as main pollutant
Share of monitored days
Ozone
318
93%
Fine particles (PM2.5)
23
7%
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
341
327
12
1
1
0
0
35
45
151
Ozone
2024
357
331
25
1
0
0
0
37
47
108
Ozone
2023
363
332
25
6
0
0
0
38
48
133
Ozone
2022
359
338
20
1
0
0
0
37
47
126
Ozone
2021
356
329
27
0
0
0
0
36
49
100
Ozone
2020
357
345
11
1
0
0
0
37
46
126
Ozone
2019
352
329
19
4
0
0
0
39
48
126
Ozone
2018
360
323
34
3
0
0
0
37
51
108
Ozone
2017
359
336
19
2
2
0
0
37
47
177
Ozone
2016
354
335
17
2
0
0
0
36
47
126
Ozone
2015
260
235
23
2
0
0
0
32
50
112
Ozone
2014
358
335
23
0
0
0
0
35
47
87
Ozone
2013
317
283
32
2
0
0
0
36
51
129
Ozone
2012
252
207
33
10
2
0
0
38
64
187
Ozone
2011
286
236
41
7
1
1
0
41
59
208
Ozone
2010
266
209
47
8
2
0
0
42
67
187
Ozone
2009
205
171
30
4
0
0
0
34
58
126
Ozone
2008
242
164
69
6
3
0
0
44
77
190
Ozone
2007
232
171
55
3
3
0
0
41
74
172
Ozone
2006
232
171
51
6
2
2
0
41
74
207
Ozone
2005
226
164
42
16
3
1
0
43
90
201
Ozone
2004
241
181
53
7
0
0
0
40
74
126
Ozone
2003
100
70
30
0
0
0
0
32
67
90
PM2.5
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 Massachusetts with a similar median AQI in 2025
