Delaware County, Iowa air quality history

Daily Air Quality Index summaries from EPA monitors in Delaware, Iowa, 1987–2017.

77%

Good days in 2016

Median daily AQI, 2016

Days above 100 in 2016

128

Days with an AQI in 2016 (of 366)

In 2016, EPA reported a daily Air Quality Index (AQI) for Delaware, Iowa on 128 days. 99 of those days (77%) were in the Good range, and the median daily AQI was 31. That median is lower than the typical monitored county in Iowa (median 43 across 18 counties), and lower than the typical monitored U.S. county (41). The main pollutant was fine particles (PM2.5) on 107 days.

EPA did not report an AQI for every day of 2016 here (128 of 366 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

The most recent year with data for this county is 2017; EPA's files for 2018–2025 contain no row for it, which usually means its monitors stopped reporting.

Years with fewer than 120 monitored days (2008, 2009, 2010, 2013, 2015, 2017…) 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, 2016

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)	107	84%
Coarse particles (PM10)	21	16%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Median AQI	90th pct.	Max AQI	Main pollutant
2017	54	43	11	0	29	53	70	PM2.5
2016	128	99	29	0	31	58	81	PM2.5
2015	118	80	38	0	38	58	76	PM2.5
2014	126	76	50	0	43	61	80	PM2.5
2013	119	70	49	0	46	64	90	PM2.5
2012	124	75	49	0	42	65	79	PM2.5
2011	120	62	58	0	48	69	86	PM2.5
2010	114	113	1	0	15	32	53	PM10
2009	113	113	0	0	14	26	44	PM10
2008	117	54	62	1	51	68	104	PM2.5
2007	41	20	20	1	52	88	140	PM2.5
2006	53	53	0	0	15	28	45	PM10
2005	57	57	0	0	14	28	44	PM10
2004	57	57	0	0	12	23	36	PM10
2003	56	56	0	0	14	27	35	PM10
2002	55	55	0	0	14	28	39	PM10
2001	57	57	0	0	14	25	42	PM10
2000	45	45	0	0	15	26	46	PM10
1999	41	41	0	0	15	27	36	PM10
1998	49	48	1	0	17	32	52	PM10
1997	50	50	0	0	18	34	48	PM10
1996	53	52	1	0	18	35	51	PM10
1995	12	12	0	0	20	32	38	PM10
1994	12	12	0	0	17	26	39	PM10
1993	50	50	0	0	16	27	46	PM10
1992	49	49	0	0	16	33	40	PM10
1991	51	51	0	0	16	24	35	PM10
1990	29	28	1	0	12	31	95	PM10
1989	45	44	1	0	16	28	56	PM10
1988	54	53	1	0	17	38	69	PM10
1987	21	21	0	0	16	25	46	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.

Counties in Iowa with a similar median AQI in 2016

All monitored counties in Iowa

Source: U.S. EPA AirData, “Annual AQI by County” files for 1987–2017 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem