Union County, New Jersey air quality history

Daily Air Quality Index summaries from EPA monitors in Union, New Jersey, 1980–2025.

61%

Good days in 2025

Median daily AQI, 2025

Days above 100 in 2025

363

Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Union, New Jersey on 363 days. 222 of those days (61%) were in the Good range, and the median daily AQI was 44. That median is higher than the typical monitored county in New Jersey (median 40 across 15 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 283 days. Across the years with fuller monitoring, the share of Good days rose: an average of 42% in 1980–1982 versus 56% 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)	283	78%
Nitrogen dioxide (NO₂)	79	22%
Carbon monoxide (CO)	1	<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	363	222	140	1	0	0	44	61	111	PM2.5
2024	366	229	137	0	0	0	43	61	85	PM2.5
2023	365	163	197	1	3	1	52	69	227	PM2.5
2022	365	191	174	0	0	0	49	65	82	PM2.5
2021	365	157	207	1	0	0	52	66	139	PM2.5
2020	366	198	167	1	0	0	48	61	111	PM2.5
2019	365	167	198	0	0	0	52	63	100	PM2.5
2018	365	156	209	0	0	0	52	64	96	PM2.5
2017	365	144	220	1	0	0	53	67	101	PM2.5
2016	366	152	214	0	0	0	52	66	90	PM2.5
2015	365	146	217	2	0	0	53	69	107	PM2.5
2014	365	141	220	4	0	0	54	66	141	PM2.5
2013	365	153	211	1	0	0	52	70	107	PM2.5
2012	364	156	208	0	0	0	53	70	96	PM2.5
2011	364	107	250	7	0	0	56	77	118	PM2.5
2010	365	147	214	4	0	0	54	77	108	PM2.5
2009	365	121	243	1	0	0	55	75	109	PM2.5
2008	366	89	273	4	0	0	57	79	105	PM2.5
2007	365	73	278	13	1	0	59	86	158	PM2.5
2006	365	84	259	21	1	0	60	92	152	PM2.5
2005	365	103	245	17	0	0	60	83	135	PM2.5
2004	366	101	251	13	1	0	59	84	152	PM2.5
2003	365	93	260	10	2	0	60	87	153	PM2.5
2002	365	87	260	16	2	0	60	91	173	PM2.5
2001	365	93	255	17	0	0	62	90	137	PM2.5
2000	366	93	251	21	1	0	62	92	167	NO2
1999	365	110	242	13	0	0	57	86	136	NO2
1998	365	160	196	9	0	0	53	81	124	NO2
1997	365	156	186	18	5	0	53	90	185	NO2
1996	365	184	164	15	1	1	50	84	209	NO2
1995	365	177	170	12	6	0	51	87	179	NO2
1994	365	146	179	34	6	0	55	101	195	NO2
1993	365	178	165	18	4	0	52	86	174	NO2
1992	366	148	195	17	5	1	55	87	201	NO2
1991	365	182	152	24	6	1	51	96	203	NO2
1990	364	182	156	21	5	0	51	90	197	NO2
1989	365	162	160	39	4	0	52	102	195	NO2
1988	366	144	164	27	15	16	57	136	241	NO2
1987	364	138	173	23	16	14	58	136	259	NO2
1986	365	146	169	28	18	4	58	115	234	CO
1985	365	93	202	48	17	5	71	119	233	NO2
1984	366	90	202	52	17	5	71	116	230	NO2
1983	364	101	172	59	19	13	68	140	276	NO2
1982	357	94	196	44	15	8	68	122	223	NO2
1981	358	215	102	28	10	3	45	104	210	NO2
1980	350	137	145	30	23	15	58	156	233	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 New Jersey with a similar median AQI in 2025

All monitored counties in New Jersey

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