Prefecture | Number of stations | Annual mean ozone concentrations (ppb) (1-hr*, max-hr) | ||||||||
2006 | 2007 | 2008 | 2009 | |||||||
1 | Hokkaido | 23 | 28.8 | 38.1 | 28.5 | 38.2 | 29.6 | 39.0 | 31.4 | 40.5 |
2 | Aomori | 6 | 36.7 | 48.0 | 36.5 | 47.0 | 32.7 | 42.2 | 32.3 | 42.2 |
5 | Akita | 5 | 35.8 | 45.4 | 38.0 | 48.4 | 36.8 | 47.3 | 37.5 | 47.3 |
6 | Yamagata | 10 | 32.3 | 44.3 | 34.1 | 46.1 | 32.7 | 43.9 | 32.9 | 44.0 |
15 | Niigata | 28 | 33.9 | 46.4 | 36.5 | 49.6 | 35.8 | 47.9 | 37.4 | 49.0 |
16 | Toyama | 25 | 36.4 | 51.3 | 36.4 | 50.6 | 35.0 | 48.4 | 33.7 | 45.5 |
17 | Ishikawa | 22 | 35.0 | 46.9 | 37.2 | 49.5 | 36.9 | 49.1 | 38.5 | 50.0 |
18 | Fukui | 22 | 31.8 | 45.5 | 32.0 | 45.8 | 33.6 | 47.7 | 33.0 | 45.6 |
31 | Tottori | 3 | 34.0 | 45.3 | 34.3 | 45.7 | 33.7 | 45.3 | 36.3 | 47.3 |
32 | Shimane | 7 | 36.9 | 49.7 | 38.3 | 50.1 | 36.6 | 48.7 | 37.9 | 49.3 |
35 | Yamaguchi | 19 | 30.3 | 47.2 | 34.6 | 52.3 | 32.9 | 48.9 | 35.4 | 51.1 |
40 | Fukuoka | 40 | 29.7 | 45.5 | 33.8 | 49.9 | 30.3 | 45.5 | 33.6 | 48.9 |
41 | Saga | 9 | 30.9 | 45.3 | 32.0 | 46.6 | 33.3 | 49.1 | 38.3 | 52.8 |
42 | Nagasaki | 18 | 34.4 | 47.3 | 36.2 | 49.1 | 33.8 | 46.2 | 37.6 | 50.3 |
43 | Kumamoto | 20 | 28.2 | 42.5 | 32.3 | 47.4 | 30.4 | 45.4 | 35.3 | 50.7 |
46 | Kagoshima | 9 | 33.9 | 48.0 | 34.6 | 47.8 | 32.2 | 45.1 | 36.5 | 50.2 |
47 | Okinawa | 4 | 27.3 | 34.7 | 27.7 | 34.0 | 27.3 | 34.3 | 33.8 | 41.5 |