Historical Exceedance Days in New England

The chart below shows the number of days air quality monitors in each New England state recorded ozone concentrations exceeding the 2008 8-hour ozone standard (that is, days greater than 0.075 parts per million (ppm)), as well as the number of days exceeding the 2015 8-hour ozone standard (that is, days greater than 0.070 ppm).

Graph Data

Exceedance Days Per Area
Year	Pollutant	New England # days >		Connecticut # days >		Maine # days >		Massachusetts # days >		New Hampshire # days >		Rhode Island # days >		Vermont # days >
Year	Pollutant	0.075	0.070	0.075	0.070	0.075	0.070	0.075	0.070	0.075	0.070	0.075	0.070	0.075	0.070
2025*	Ozone (O₃)	17	25	16	22	4	5	4	5	1	5	4	3	0	1
2024	Ozone (O₃)	15	24	14	23	1	2	1	5	0	1	2	3	0	0
2023	Ozone (O₃)	12	21	11	20	0	0	6	10	2	4	5	7	0	2
2022	Ozone (O₃)	14	24	12	23	1	2	1	4	1	2	3	5	0	0
2021	Ozone (O₃)	18	23	16	21	3	4	2	4	2	3	2	5	0	0
2020	Ozone (O₃)	9	18	9	17	0	1	1	3	0	0	2	4	0	0
2019	Ozone (O₃)	14	24	12	21	0	1	2	5	0	1	1	2	0	0
2018	Ozone (O₃)	18	28	17	23	2	3	6	12	1	6	5	12	0	1
2017	Ozone (O₃)	17	25	10	20	5	6	6	12	3	5	5	6	0	1
2016	Ozone (O₃)	21	32	21	31	1	4	7	11	0	5	4	6	0	1
2015	Ozone (O₃)	24	38	22	33	2	4	3	15	3	7	4	10	0	0
2014	Ozone (O₃)	9	20	8	16	0	3	0	4	1	4	0	2	0	0
2013	Ozone (O₃)	20	27	18	23	5	8	6	13	3	6	7	11	0	1
2012	Ozone (O₃)	29	39	37	36	4	5	17	27	3	12	11	17	0	1
2011	Ozone (O₃)	16	24	14	20	3	7	10	15	2	4	6	11	1	1
2010	Ozone (O₃)	29	45	24	37	8	9	14	23	8	11	6	11	0	3
2009	Ozone (O₃)	11	19	6	18	3	5	8	11	2	5	1	6	0	3
2008	Ozone (O₃)	39	45	22	32	4	10	18	29	10	20	6	13	3	4
2007	Ozone (O₃)	53	62	42	54	14	17	38	48	22	24	18	28	5	7
2006	Ozone (O₃)	37	45	29	34	10	16	26	34	11	18	13	19	0	3
2005	Ozone (O₃)	43	57	30	41	15	22	31	47	17	26	17	23	4	10
2004	Ozone (O₃)	28	38	20	26	11	17	16	29	10	15	5	12	4	5
2003	Ozone (O₃)	34	51	26	37	15	19	27	38	10	21	13	18	4	7
2002	Ozone (O₃)	53	60	49	55	28	29	43	56	23	30	33	37	13	19
2001	Ozone (O₃)	47	59	39	41	22	30	37	48	22	31	26	33	9	16
2000	Ozone (O₃)	27	39	23	31	5	14	16	25	5	6	14	17	2	6
1999	Ozone (O₃)	50	62	43	54	21	27	36	47	19	29	16	22	11	18
1998	Ozone (O₃)	52	69	44	53	22	36	36	51	14	19	11	18	5	11
1997	Ozone (O₃)	47	58	34	44	16	25	38	48	16	23	19	19	11	9
1996	Ozone (O₃)	44	56	33	39	20	29	28	38	14	21	12	14	4	10
1995	Ozone (O₃)	48	60	35	44	23	32	33	48	19	27	18	22	13	13
1994	Ozone (O₃)	53	70	39	57	22	27	39	49	21	33	21	28	13	11
1993	Ozone (O₃)	51	60	39	49	20	26	40	51	18	25	11	14	9	13
1992	Ozone (O₃)	47	62	29	38	22	27	36	49	16	20	12	20	11	13
1991	Ozone (O₃)	54	69	46	57	26	33	45	52	22	25	28	31	16	21
1990	Ozone (O₃)	57	68	44	56	21	29	37	50	20	28	18	24	8	17
1989	Ozone (O₃)	62	77	41	55	29	27	43	44	14	23	14	22	5	9
1988	Ozone (O₃)	72	79	62	70	40	46	63	65	37	42	29	40	26	35
1987	Ozone (O₃)	58	74	44	57	20	27	35	46	29	34	27	34	11	16
1986	Ozone (O₃)	53	67	41	57	17	19	32	43	16	16	22	29	6	10
1985	Ozone (O₃)	70	85	58	72	35	47	53	68	15	21	27	38	9	14
1984	Ozone (O₃)	79	88	63	70	34	42	65	72	19	25	42	51	10	14
1983	Ozone (O₃)	113	118	103	111	36	43	84	95	19	29	34	40	7	12

*2025 data preliminary and subject to change.