Radon and home risks by county
Radon in New Jersey
7 of New Jersey's 21 counties are in EPA's highest radon zone, home to about 24% of the state's residents. Radon zones describe an area's potential; EPA recommends testing every home regardless of zone.
Zone 1 counties
7
high radon potential
Zone 2 counties
11
moderate potential
Zone 3 counties
3
low potential
Counties with water violations
20
since 2016; 5 with unresolved ones
Find your county by ZIP
Zone 1: high potential (7 counties)
| County | Residents | Water systems | Health violations since 2016 | Unresolved |
|---|---|---|---|---|
| Hunterdon County | 131,708 | 26 | 4 | 1 |
| Mercer County | 392,138 | 11 | 10 | 0 |
| Monmouth County | 647,520 | 39 | 6 | 0 |
| Morris County | 523,053 | 64 | 51 | 5 |
| Somerset County | 357,467 | 5 | 1 | 0 |
| Sussex County | 147,444 | 61 | 31 | 2 |
| Warren County | 112,031 | 24 | 2 | 1 |
Zone 2: moderate potential (11 counties)
| County | Residents | Water systems | Health violations since 2016 | Unresolved |
|---|---|---|---|---|
| Bergen County | 978,641 | 22 | 9 | 0 |
| Burlington County | 475,515 | 49 | 19 | 0 |
| Camden County | 533,988 | 22 | 3 | 0 |
| Cumberland County | 155,678 | 14 | 23 | 0 |
| Essex County | 881,527 | 21 | 50 | 0 |
| Gloucester County | 311,783 | 29 | 17 | 0 |
| Hudson County | 736,185 | 7 | 2 | 0 |
| Middlesex County | 890,119 | 16 | 15 | 0 |
| Passaic County | 526,597 | 29 | 14 | 0 |
| Salem County | 65,874 | 15 | 17 | 0 |
| Union County | 594,160 | 5 | 0 | 0 |
Zone 3: low potential (3 counties)
| County | Residents | Water systems | Health violations since 2016 | Unresolved |
|---|---|---|---|---|
| Atlantic County | 279,114 | 29 | 7 | 0 |
| Cape May County | 93,875 | 25 | 5 | 1 |
| Ocean County | 666,434 | 57 | 6 | 0 |
How to read this table
Water systems counts community systems that list the county in their service area; one system can serve several counties. Health violations are breaches of a legal limit or treatment rule recorded by EPA since January 2016, not paperwork lapses. A violation stays unresolved until the state records it as fixed.
Other states
Sources: EPA Map of Radon Zones, EPA ECHO Safe Drinking Water Act data (2026Q3, published October 2026), US Census Bureau Vintage 2024 estimates. See the methodology.