Radon Levels in DuPage County & Illinois: What IEMA Data Shows
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Illinois' radon program is run by the Illinois Emergency Management Agency (IEMA), which publishes results reported by licensed radon measurement professionals on a public dashboard. We pulled those results in October 2026 for 26 cities in and around DuPage County and counted valid tests on homes without a mitigation system.
The EPA numbers that matter
- 4.0 pCi/L is EPA's action level: fix the home at or above it.
- EPA suggests considering a fix between 2 and 4 pCi/L, since there is no known safe level.
- EPA calls radon the leading cause of lung cancer among non-smokers.
Share of tests at or above 4.0 pCi/L, by city
Across all 26 cities: 40,143 of 94,555 tests (42%) were at or above 4.0 pCi/L.
| City (test address) | Valid tests | ≥ 4.0 pCi/L | ≥ 8.0 pCi/L |
|---|---|---|---|
| Romeoville | 1,087 | 62% | 34% |
| West Chicago | 1,514 | 53% | 19% |
| Montgomery | 1,164 | 52% | 22% |
| Lisle | 2,390 | 50% | 22% |
| Plainfield | 8,620 | 50% | 21% |
| Wheaton | 6,869 | 47% | 19% |
| Bolingbrook | 3,453 | 46% | 21% |
| Oswego | 2,955 | 45% | 19% |
| Downers Grove | 5,179 | 44% | 18% |
| Naperville | 23,028 | 44% | 16% |
| Glen Ellyn | 4,766 | 43% | 16% |
| Warrenville | 753 | 41% | 20% |
| Roselle | 965 | 40% | 16% |
| Darien | 1,705 | 38% | 14% |
| Lombard | 2,840 | 38% | 15% |
| Westmont | 1,394 | 38% | 15% |
| Woodridge | 1,754 | 37% | 14% |
| Oak Brook | 1,214 | 37% | 13% |
| Aurora | 9,976 | 37% | 12% |
| Hinsdale | 3,236 | 37% | 11% |
| Addison | 773 | 36% | 14% |
| Bloomingdale | 1,506 | 34% | 14% |
| Elmhurst | 4,289 | 33% | 10% |
| Villa Park | 1,128 | 29% | 10% |
| Carol Stream | 1,522 | 28% | 9% |
| Glendale Heights | 475 | 24% | 7% |
How to read these numbers
These are not a random survey. Most tests are ordered for home sales or by worried homeowners, and a city name on a test address doesn't always match municipal limits. Use them to see that elevated radon is common here, not to predict your house. Neighbors on the same street can test very differently. Test your own home.
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