| Values | Quality |
| Igeo < 0 | Unpolluted |
| 0 < Igeo < 1 | Unpolluted to moderately polluted |
| 1 < Igeo < 2 | Moderately polluted |
| 2 < Igeo < 3 | Moderately polluted to highly polluted |
| 3 < Igeo < 4 | Highly polluted |
| 4 < Igeo < 5 | Highly polluted to very highly polluted |
| 5 < Igeo | Very highly polluted |