Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Grading scale for geo-accumulation index (Igeo)
| Index class | Unpolluted | Unpolluted to moderate pollution | Moderately polluted | Moderately to strong pollution | Strongly polluted | Strongly to extreme pollution | Extremely polluted |
|---|---|---|---|---|---|---|---|
| Class | Class 0 | Class 1 | Class 2 | Class 3 | Class 4 | Class 5 | Class 6 |
| Range | Igeo ≤ 0 | 0 > Igeo ≤ 1 | 1 > Igeo ≤ 2 | 2 > Igeo ≤ 3 | 3 > Igeo ≤ 4 | 4 > Igeo ≤ 5 | Igeo > 5 |
