5 cities covered
Illinois water quality and radon, by city
2 of 5 covered Illinois cities use chloramine in at least part of the system, and 5 have hard water. 56 of Illinois's 102 counties are EPA radon zone 1.
| City | Disinfectant | Hardness | Lead | PFAS | Radon |
|---|---|---|---|---|---|
| Chicago | Chlorine | 8.1 gpg | 7 ppb | Not detected | Zone 2 |
| Aurora | Chloramine | 16.8 gpg | 24 ppb | Detected | Zone 1 |
| Naperville | Chlorine | 7.0 gpg | 7.1 ppb | Not detected | Zone 2 |
| Joliet | Chloramine | 14.3 gpg | 6.5 ppb | Not detected | Zone 2 |
| Rockford | Chlorine | 19.3 gpg | 7.3 ppb | Detected | Zone 1 |
Illinois radon zones
Zone 1 (highest)56 counties
Zone 243 counties
Zone 3 (lowest)3 counties