Union County, Tennessee air quality history

Daily Air Quality Index summaries from EPA monitors in Union, Tennessee, 1988–2016.

94%

Good days in 2015

Median daily AQI, 2015

Days above 100 in 2015

365

Days with an AQI in 2015 (of 365)

In 2015, EPA reported a daily Air Quality Index (AQI) for Union, Tennessee on 365 days. 344 of those days (94%) were in the Good range, and the median daily AQI was 19. That median is lower than the typical monitored county in Tennessee (median 42.5 across 18 counties), and lower than the typical monitored U.S. county (41). The main pollutant was coarse particles (PM10) on 365 days. Across the years with fuller monitoring, the share of Good days rose: an average of 69% in 1997–1999 versus 97% in 2013–2015.

The most recent year with data for this county is 2016; EPA's files for 2017–2025 contain no row for it, which usually means its monitors stopped reporting.

Years with fewer than 120 monitored days (1992, 1993, 1994, 1995, 1996, 2016…) 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, 2015

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
Coarse particles (PM10)	365	100%

Year-by-year data

Annual AQI summary by year
Year	Days with AQI	Good	Moderate	Unhealthy for Sensitive Groups	Unhealthy	Median AQI	90th pct.	Max AQI	Main pollutant
2016	20	20	0	0	0	11	17	19	PM10
2015	365	344	21	0	0	19	43	96	PM10
2014	365	355	10	0	0	19	37	74	PM10
2013	358	353	5	0	0	18	36	70	PM10
2012	366	355	11	0	0	21	37	71	PM10
2011	364	343	21	0	0	22	45	67	PM10
2010	361	336	25	0	0	23	47	75	PM10
2009	360	356	4	0	0	20	35	61	PM10
2008	365	315	50	0	0	24	53	97	PM10
2007	365	306	59	0	0	30	55	83	PM10
2006	365	306	59	0	0	31	54	77	PM10
2005	362	317	45	0	0	29	52	72	PM10
2004	356	269	85	2	0	31	61	131	PM10
2003	364	277	86	1	0	31	60	104	PM10
2002	365	305	60	0	0	27	57	96	PM10
2001	365	302	63	0	0	29	57	82	PM10
2000	365	303	61	1	0	26	55	101	PM10
1999	356	262	93	1	0	33	64	112	PM10
1998	355	233	119	3	0	39	66	111	PM10
1997	298	204	93	0	1	38	65	161	PM10
1996	85	76	9	0	0	31	51	68	PM10
1995	60	52	8	0	0	31	53	57	PM10
1994	60	53	7	0	0	30	51	59	PM10
1993	58	57	1	0	0	26	44	51	PM10
1992	55	54	1	0	0	30	43	62	PM10
1991	58	51	7	0	0	32	52	57	PM10
1990	61	53	8	0	0	31	51	72	PM10
1989	61	56	5	0	0	27	47	64	PM10
1988	24	24	0	0	0	23	35	49	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.

All monitored counties in Tennessee

Source: U.S. EPA AirData, “Annual AQI by County” files for 1988–2016 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem