Allegany County, Maryland air quality history

Daily Air Quality Index summaries from EPA monitors in Allegany, Maryland, 1980–1998.

100%

Good days in 1992

Median daily AQI, 1992

Days above 100 in 1992

176

Days with an AQI in 1992 (of 366)

In 1992, EPA reported a daily Air Quality Index (AQI) for Allegany, Maryland on 176 days. 176 of those days (100%) were in the Good range, and the median daily AQI was 15. That median is lower than the typical monitored county in Maryland (median 42 across 11 counties), and lower than the typical monitored U.S. county (37). The main pollutant was carbon monoxide (CO) on 130 days. Across the years with fuller monitoring, the share of Good days fell: an average of 98% in 1980–1982 versus 93% in 1990–1992.

EPA did not report an AQI for every day of 1992 here (176 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 1998; EPA's files for 1999–2025 contain no row for it, which usually means its monitors stopped reporting.

Years with fewer than 120 monitored days (1993, 1994, 1995, 1996, 1997, 1998) 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, 1992

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
Carbon monoxide (CO)	130	74%
Coarse particles (PM10)	46	26%

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
1998	29	29	0	0	0	0	20	45	48	PM10
1997	61	59	2	0	0	0	23	38	53	PM10
1996	59	58	1	0	0	0	24	36	52	PM10
1995	60	58	2	0	0	0	23	42	52	PM10
1994	54	54	0	0	0	0	17	36	44	PM10
1993	60	60	0	0	0	0	21	41	49	PM10
1992	176	176	0	0	0	0	15	27	39	CO
1991	323	289	31	2	1	0	25	51	151	CO
1990	310	277	31	2	0	0	29	51	126	Ozone
1989	361	344	17	0	0	0	23	44	77	Ozone
1988	361	286	38	17	18	2	29	101	207	CO
1987	365	329	32	4	0	0	31	50	150	Ozone
1986	365	346	18	1	0	0	28	46	101	Ozone
1985	342	273	57	10	2	0	36	77	159	Ozone
1984	359	297	47	10	4	1	31	69	206	Ozone
1983	347	273	42	23	7	2	34	93	208	Ozone
1982	350	340	10	0	0	0	24	41	90	CO
1981	327	320	6	1	0	0	17	38	112	Ozone
1980	125	125	0	0	0	0	6	30	47	Ozone

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 Maryland

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–1998 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem