Polk County, Iowa air quality history

Daily Air Quality Index summaries from EPA monitors in Polk, Iowa, 1980–2025.

61%

Good days in 2025

Median daily AQI, 2025

Days above 100 in 2025

365

Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Polk, Iowa on 365 days. 224 of those days (61%) were in the Good range, and the median daily AQI was 44. That median is about the same as the typical monitored county in Iowa (median 43.5 across 14 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 263 days. Across the years with fuller monitoring, the share of Good days rose: an average of 46% in 1980–1982 versus 58% in 2023–2025.

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
Fine particles (PM2.5)	263	72%
Ozone	100	27%
Coarse particles (PM10)	2	1%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Unhealthy	Very Unhealthy	Median AQI	90th pct.	Max AQI	Main pollutant
2025	365	224	139	2	0	0	44	64	136	PM2.5
2024	366	247	119	0	0	0	45	59	93	PM2.5
2023	365	168	182	12	3	0	52	73	166	PM2.5
2022	365	273	92	0	0	0	41	57	89	PM2.5
2021	365	227	137	1	0	0	45	64	110	PM2.5
2020	366	261	103	0	2	0	42	59	199	PM2.5
2019	365	251	114	0	0	0	42	60	100	PM2.5
2018	365	225	138	2	0	0	46	62	112	PM2.5
2017	365	222	142	1	0	0	45	61	135	PM2.5
2016	366	244	121	1	0	0	44	58	138	PM2.5
2015	365	252	113	0	0	0	44	61	99	PM2.5
2014	365	227	138	0	0	0	44	62	93	PM2.5
2013	365	191	174	0	0	0	48	64	99	PM2.5
2012	366	169	197	0	0	0	52	69	100	PM2.5
2011	365	181	184	0	0	0	51	67	98	PM2.5
2010	365	180	182	3	0	0	51	72	116	PM2.5
2009	365	187	177	1	0	0	49	66	116	PM2.5
2008	366	158	207	1	0	0	52	70	113	PM2.5
2007	364	157	204	3	0	0	53	74	112	PM2.5
2006	365	203	161	1	0	0	47	67	105	PM2.5
2005	365	170	185	10	0	0	52	77	134	PM2.5
2004	366	202	161	3	0	0	48	67	104	PM2.5
2003	365	187	175	3	0	0	50	70	127	PM2.5
2002	365	184	181	0	0	0	50	72	97	PM2.5
2001	365	156	208	1	0	0	52	72	102	PM2.5
2000	366	166	198	2	0	0	52	76	107	PM2.5
1999	365	288	76	1	0	0	33	61	103	Ozone
1998	365	351	13	0	0	1	28	42	246	Ozone
1997	361	301	60	0	0	0	34	55	97	Ozone
1996	366	326	38	2	0	0	31	53	119	Ozone
1995	365	309	47	9	0	0	37	61	136	Ozone
1994	365	326	39	0	0	0	33	51	80	Ozone
1993	305	267	37	1	0	0	35	52	108	Ozone
1992	337	280	49	8	0	0	32	62	133	Ozone
1991	365	329	36	0	0	0	31	50	90	CO
1990	365	308	57	0	0	0	32	56	97	CO
1989	365	308	54	3	0	0	33	55	129	Ozone
1988	366	323	43	0	0	0	30	51	94	CO
1987	365	277	88	0	0	0	33	60	87	PM10
1986	365	264	100	0	1	0	39	60	184	PM10
1985	365	284	75	6	0	0	40	63	147	CO
1984	366	208	151	6	1	0	45	79	169	CO
1983	365	163	153	27	21	1	53	122	203	CO
1982	365	194	162	9	0	0	49	78	140	CO
1981	365	193	166	6	0	0	49	81	123	CO
1980	363	112	193	44	12	2	67	119	210	CO

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 Iowa with a similar median AQI in 2025

All monitored counties in Iowa

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem