Marshall County, West Virginia air quality history

Daily Air Quality Index summaries from EPA monitors in Marshall, West Virginia, 1996–2025.

64%

Good days in 2025

Median daily AQI, 2025

Days above 100 in 2025

284

Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Marshall, West Virginia on 284 days. 181 of those days (64%) were in the Good range, and the median daily AQI was 42. That median is higher than the typical monitored county in West Virginia (median 39 across 12 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 284 days. Across the years with fuller monitoring, the share of Good days rose: an average of 20% in 1999–2004 versus 60% in 2023–2025.

EPA did not report an AQI for every day of 2025 here (284 of 365 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.

Years with fewer than 120 monitored days (1998, 2000, 2002, 2003, 2019, 2020…) 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
Fine particles (PM2.5)	284	100%

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	284	181	103	0	0	0	42	63	81	PM2.5
2024	359	267	92	0	0	0	39	58	81	PM2.5
2023	354	149	202	1	1	1	52	68	213	PM2.5
2022	361	162	199	0	0	0	52	70	99	PM2.5
2021	353	140	212	1	0	0	53	74	121	PM2.5
2020	118	87	31	0	0	0	41	57	72	PM2.5
2019	118	68	50	0	0	0	46	63	80	PM2.5
2018	229	99	130	0	0	0	52	65	94	PM2.5
2017	365	116	249	0	0	0	55	66	85	PM2.5
2016	306	167	139	0	0	0	48	64	86	PM2.5
2015	363	176	187	0	0	0	51	65	88	PM2.5
2014	362	137	225	0	0	0	54	69	84	PM2.5
2013	365	143	222	0	0	0	54	68	91	PM2.5
2012	364	102	262	0	0	0	57	71	87	PM2.5
2011	351	122	228	1	0	0	55	76	106	PM2.5
2010	350	97	250	3	0	0	58	76	112	PM2.5
2009	365	101	264	0	0	0	56	72	88	PM2.5
2008	366	78	284	4	0	0	57	75	116	PM2.5
2007	365	66	288	11	0	0	59	86	131	PM2.5
2006	352	76	265	11	0	0	60	85	132	PM2.5
2005	121	19	100	2	0	0	63	86	143	PM2.5
2004	121	30	89	2	0	0	59	81	125	PM2.5
2003	116	24	90	1	1	0	59	81	153	PM2.5
2002	116	30	78	7	1	0	60	82	154	PM2.5
2001	121	28	89	4	0	0	61	82	117	PM2.5
2000	113	26	85	2	0	0	60	85	107	PM2.5
1999	121	16	102	3	0	0	64	85	138	PM2.5
1998	59	58	1	0	0	0	22	43	51	PM10
1997	60	59	1	0	0	0	21	43	57	PM10
1996	59	58	1	0	0	0	23	37	61	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 West Virginia with a similar median AQI in 2025

All monitored counties in West Virginia

Source: U.S. EPA AirData, “Annual AQI by County” files for 1996–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem