| Year | Weight coefficient | |||
| SO2 | NO2 | PM10 | Primary pollutant | |
| 2011 | 0.489 | 0.133 | 0.378 | SO2 |
| 2012 | 0.520 | 0.133 | 0.347 | PM10 |
| 2013 | 0.400 | 0.191 | 0.409 | PM10 |
| 2014 | 0.452 | 0.167 | 0.381 | SO2 |
| 2015 | 0.449 | 0.131 | 0.420 | SO2 |
| 2016 | 0.427 | 0.185 | 0.387 | SO2 |