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| SO2(Index ≤ 202) | COD(Index ≤ 239) | ||||||
|---|---|---|---|---|---|---|---|
| Year | Province | Eastern regions | Central-western regions | Year | Province | Eastern regions | Central-western regions |
| 2011 | 31 | 11 | 20 | 2011 | 31 | 11 | 20 |
| 2012 | 31 | 11 | 20 | 2012 | 31 | 11 | 20 |
| 2013 | 28 | 8 | 20 | 2013 | 31 | 11 | 20 |
| 2014 | 26 | 6 | 20 | 2014 | 29 | 9 | 20 |
| 2015 | 5 | 1 | 4 | 2015 | 25 | 5 | 20 |
