Ozone Trends in Southern California

HISTORIC OZONE AIR QUALITY TRENDS

In the South Coast Air Basin, 1976-2001

Number of Days Exceeding Health Standard Levels^a)

Year	State Standard (1-hour average > 0.09 ppm)	Federal Standard (1-hour average > 0.12 ppm)	Federal Standard (8-hour average > 0.085 ppm)	Health Advisory (1-hour average ł 0.15 ppm)	Stage 1 Episode (1-hour average ł 0.20 ppm)	Stage 2 Episode (1-hour average ł 0.35 ppm)	Basin Maximum (ppm)
1976	237	194	206	166	102	7	0.38
1977	242	208	223	184	121	11	0.39
1978	217	187	200	173	116	23	0.43
1979	226	191	204	169	120	17	0.45
1980	210	167	186	152	101	15	0.41
1981	222	180	198	159	99	5	0.37
1982	191	149	168	121	63	2	0.40
1983	190	152	169	138	84	3	0.39
1984	207	173	194	146	97	0	0.34
1985	206	158	188	136	83	7	0.39
1986	217	164	194	140	79	1	0.35
1987	196	160	182	130	66	0	0.33
1988	216	178	197	144	77	1	0.35
1989	211	157	186	120	54	0	0.34
1990	184	130	163	107	41	0	0.33
1991	183	130	162	100	47	0	0.32
1992	191	143	176	109	41	0	0.30
1993	185	124	170	92	24	0	0.28
1994	165	118	152	96	23	0	0.30
1995	154	98	127	59	14	0	0.26
1996	151	90	132	53	7	0	0.24
1997	141	68	127	28	1	0	0.21
1998	114	62	111	43	12	0	0.24
1999	118	41	113	12	0	0	0.17
2000	122	39	111	17	0	0	0.18
2001	121	36	100	15	0	0	0.19

ppm = parts per million parts of air, by volume.

a) Represents the number of days a standard was exceeded anywhere in the South Coast Air Basin.

AQMD Home Page
This page updated: March 01, 2004
URL: http://www.aqmd.gov/news1/ozone_trends.htm