| Igeo | Pollution characterization |
| >5 | extremely polluted |
| 4 - 5 | strongly to extremely polluted |
| 3 - 4 | strongly polluted |
| 2 - 3 | moderately to strongly polluted |
| 1 - 2 | moderately polluted |
| 0 - 1 | unpolluted to moderately polluted |
| <0 | unpolluted |