Below is a code that is on the map, but here is the explanation.
1. Barley polluted water, safety 95%
2. Polluted water, safety 50%
3. Very Polluted water, safety 25%
4. Extreme Polluted water, safety 10%
5. Little or non-polluted land, safety 95-100%
6. Polluted or destroyed land, safety 95-50%, fixable (e.g. scorched forest)
7. desolate land, safety <50%, non-fixable (e.g. desertification)