Radon Levels & Zone Map in Nassau County, NY
Direct Answer for basement and lowest-level tests: Nassau County has a lower countywide signal, but that does not clear an individual home. A real test still beats the map.
Low county risk is not a home-level clear signal
Do not let a Zone 3 label talk you out of the first test. House-by-house differences still matter.
Lower countywide map signal, but house-by-house spikes still happen.
2.0-3.9 pCi/L usually means retest or track. 4.0+ is where EPA action and quote planning start to matter.
Low zone is not a free pass. Use a kit before you rule radon out.
Measured Radon Data
Nassau County evidence before the next step
Nassau County, NY has more than the EPA map: NY DOH exposes 54 reported tests, 1.7 pCi/L county average, 16.2% of reported tests at or above 4.0 pCi/L, and 5.4 pCi/L high-end signal for 2015-2019.
Source window
2015-2019
Processed verdict
Borderline measured burden
High confidence - 86/100
Primary result
1.7 pCi/L
15th percentile in-state
4.0+ signal
16.2%
26th percentile in-state
High-end signal
5.4 pCi/L
15th percentile in-state
County-specific verdict
Nassau County is a retest-and-watch market, not a dismiss-it market.
Nassau County is a confirmation case because 1.7 pCi/L average, and 16.2% of reported tests at or above 4.0. In-state rank: 15th percentile for average, and 26th percentile for 4.0+ share. A 2.0-3.9 result should not be treated as final without a follow-up test or longer-term read.
Real-estate use
Buyer or seller use: use the county signal to justify a test contingency or retest, then reserve credits for confirmed 4.0+ home results.
Nassau County is a split-decision county: no reading means test first, 2.0-3.9 means retest or track, and 4.0+ means cost planning starts.
Choose Next StepBorderline-intent answer
What does a borderline radon result mean in Nassau County?
Nassau County is a split-decision county. 16.2% of reported tests at or above 4.0 pCi/L, 1.7 pCi/L primary measured result, and 5.4 pCi/L high-end signal means a 2.0-3.9 pCi/L home result should be retested or tracked instead of dismissed.
Pick the situation that matches you
You should not need to read the whole guide before clicking one of these. Start with the lane that matches your current stage, then come back for the deeper reference only if you still need it.
Jump into a prefilled Nassau County action plan based on the result you already have, instead of starting from a generic cost page.
I have not tested yet
Do not price mitigation blind. Get the first number, then decide whether you need monitoring, quotes, or nothing at all.
My result is 2.0-3.9
Usually retest or track first. If the reading keeps showing up, use the local action plan to decide whether pricing makes sense.
My result is 4.0+
This is the EPA action line. Use the local cost page before calling contractors so you know the likely scope, timing, and budget.
I am buying or selling
Turn the reading into a credit or repair number before negotiation starts. This is the faster path than arguing from a generic article.
Already tested once and just want to watch the number trend?
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County Evidence Snapshot
Nassau County testing context
Nassau County has a lower predicted countywide zone signal, so direct testing matters more than the map label.
EPA map signal
Zone 3
County-level predicted indoor screening range, not a home-level test result.
Housing base
476,982
92th percentile among 62 NY counties with data.
Older housing share
13.6%
2th percentile in-state; older homes often need clearer test placement decisions.
Median home value
$633,800
Used as context for whether mitigation is a small maintenance item or a negotiation issue.
Measured Radon Data
New York State Department of Health Residential Radon Test Data
2015-2019
Average result
1.7 pCi/L
At or above 4.0
16.2%
Maximum reported
5.4 pCi/L
Avg. tests/year
10.8
NY DOH county summaries are based on submitted residential radon tests and are not a statistically designed survey of every home.
RadonVerdict Processed Verdict
Borderline measured burden
Primary result rank
15th percentile
1.7 pCi/L
4.0+ rank
26th percentile
16.2% at or above 4.0
High-end rank
15th percentile
5.4 pCi/L
Test volume rank
37th percentile
10.8 avg/year
How to use this county data
Data source
Official county measurements
NY DOH values are submitted residential tests; higher testing participation can make the volume signal especially useful for local context.
What the numbers show
Fuller county picture
This is the most useful setup: county average, 4.0+ share, high-end readings, and 54 reported tests/properties can be read together instead of relying on one number.
Nearby comparison
Nearby comparison: Closest counties by county average: Clinton County (1.7 pCi/L) is just lower, and Rockland County (2.0 pCi/L) is just higher.
How this helps
Use this for 2.0-3.9 pCi/L results, where retesting is usually smarter than dismissing the issue.
What the data says
Nassau County, NY is measurement-backed for 2015-2019. The measured average is 1.7 pCi/L, and 16.2% of reported results are at or above 4.0 pCi/L. The high-end signal reaches 5.4 pCi/L.
Nassau County, NY sits at the 15th percentile for measured average, 26th percentile for 4.0+ share, 15th percentile for high-end readings, and 37th percentile for test volume among 62 measured counties in the state. Closest counties by county average: Clinton County (1.7 pCi/L) is just lower, and Rockland County (2.0 pCi/L) is just higher.
What to do with it
Nassau County is a split-decision county: no reading means test first, 2.0-3.9 means retest or track, and 4.0+ means cost planning starts.
Retest trigger: a 2.0-3.9 pCi/L home result is exactly the gray zone for this county; retest before ignoring it or paying for mitigation.
High confidence (86/100) from NY DOH based on about 54 reported tests/properties plus comparable county-level measurement fields.
No reading yet
No reading yet: start with a test kit; the county data is context, not a substitute for the home result.
2.0-3.9 result
2.0-3.9 pCi/L: retest or monitor before paying for mitigation, then escalate if the level repeats or rises.
4.0+ result
4.0+ pCi/L: use the result for mitigation quotes, repair scope, or seller-credit negotiation; the county signal is no longer the deciding input.
Source hierarchy: NY DOH is used for this county, with EPA zone and Census housing data kept as supporting context. NY DOH values are submitted residential tests; higher testing participation can make the volume signal especially useful for local context.
Direct Answer
What radon risk level should homeowners assume in Nassau County?
Nassau County is currently categorized as EPA Zone 3 (Lower Predicted Average Risk). Testing is still recommended because home-level variance can be high.
| Evidence | Value |
|---|---|
| Area | Nassau County, NY |
| EPA Zone | Zone 3 |
| Primary Recommendation | Perform direct radon testing in the lowest livable level |
Your Radon Reading
Enter your home's measured level; the starting value is only a planning example until you have your own result.
Lower Concern Range
Your reading is below the common action reference levels. Both the EPA (4.0) and WHO (2.7) thresholds are not exceeded. Mitigation is usually not the next immediate step after a confirmed low result. If you have never tested your home, start with a short-term kit first. If this is already a confirmed low reading, a digital monitor can help you keep an eye on seasonal changes.
Understanding Radon Levels: Complete Reference
Below 2.0 pCi/L - Lower Concern, Keep Testing
Below both the EPA (4.0) and WHO (2.7) action reference levels. This usually means mitigation is not the next immediate step after a confirmed result. The average outdoor radon level is approximately 0.4 pCi/L, and there is no known risk-free indoor level. Periodic testing is still recommended because levels can change over time due to seasonal variations, changes in home ventilation, or foundation settling.
-4.0
2.0 - 4.0 pCi/L - Elevated, Consider Action
Exceeds the World Health Organization's reference level of 2.7 pCi/L but falls below the US EPA action threshold. The EPA states that homeowners should "consider fixing" homes in this range, especially if the home has a basement used as living space, if children are present, or in connection with a real estate transaction. Practical next step: run a confirmatory long-term test, then compare mitigation quotes if levels remain elevated.
-8.0
4.0 - 8.0 pCi/L - Action Recommended
Exceeds the EPA action level of 4.0 pCi/L. The EPA and Surgeon General strongly recommend mitigation within a few months. At this level, prioritize confirmatory testing and contractor planning. Standard sub-slab depressurization systems typically reduce indoor levels by 80-99%.
Above 8.0 pCi/L - Urgent Action Required
At these levels, the EPA recommends expedited mitigation - ideally within weeks, not months. Occupants should minimize time in lower-level rooms until the system is installed. Use a certified mitigator and request priority scheduling to shorten high-exposure time. Many mitigators offer priority scheduling for homes above 8.0 pCi/L.
Why Radon is Still Relevant in Nassau County
Nassau County is classified as EPA Zone 3, with a lower predicted indoor screening range below 2.0 pCi/L. This does not mean radon is absent - it means the countywide map signal is low.
The EPA has documented elevated radon readings in every state and in homes in every zone classification. Local geological anomalies - pockets of granite, shale intrusions, or fractured bedrock - can create localized high-radon areas even within an otherwise low-risk county.
The Surgeon General and EPA recommend testing all homes, regardless of geographic zone. A simple short-term test kit ($15-$30) provides results within a few days and can give you peace of mind.
Radon & Health: What the Science Says
lung cancer
from radon
4.0 pCi/L
Radon is a Class A carcinogen - the same classification as asbestos and tobacco smoke. The National Academy of Sciences estimates that radon causes approximately 21,000 lung cancer deaths annually in the United States, making it the leading environmental cause of cancer death.
Unlike smoking, radon exposure is involuntary and often invisible. There is no safe level of radon - risk increases linearly with exposure. The good news: radon mitigation systems are highly effective, typically reducing indoor levels by 80-99% within hours of activation.
Source: US Environmental Protection Agency, "A Citizen's Guide to Radon" (EPA 402/K-12/002). National Academy of Sciences, Biological Effects of Ionizing Radiation (BEIR VI) Report, 1999.
Step 1: Test Your Home
Testing is the only way to know your home's radon level. Zone data tells you the regional risk, but your home could be significantly higher or lower than the countywide pattern. For most homeowners, the right first purchase is a low-cost short-term test kit.
A digital monitor is a better fit after your first result, for seasonal re-checks, or to keep tracking levels after mitigation.
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Already Know Your Level?
If your test shows 4.0 pCi/L or higher, get an itemized cost estimate specific to Nassau County - including regional labor rates and permit requirements.
Get Mitigation Cost Estimate ->NY Radon Regulations
New York does not have a state-mandated radon disclosure requirement, but sellers must complete the Property Condition Disclosure Statement, and failing to disclose known issues can create legal liability.
New York does not require state licensing for radon professionals, but the NRPP and AARST certifications are industry standard.
How to Test for Radon in Nassau County
Buy a Test Kit
Purchase a short-term charcoal test kit online or from a local hardware store. Cost: $15-$30. Place it in the lowest livable level of your home.
Wait 2-7 Days
Keep doors and windows closed (except normal entry/exit) during the test period. Avoid running whole-house fans. Mail the kit to the lab provided.
Read Your Results
If results are below 4.0 pCi/L, re-test every 2 years or use a monitor for ongoing tracking. If above 4.0, use our cost calculator to see mitigation options.
Related Radon Resources for Nassau County
Explore Other NY Counties
Official State Resource
New York radon program and rules
Use the state program link to verify local radon guidance, disclosure language, and contractor credential expectations before you act on an estimate.
Disclosure note
New York does not have a state-mandated radon disclosure requirement, but sellers must complete the Property Condition Disclosure Statement, and failing to disclose known issues can create legal liability.
Credential note
New York does not require state licensing for radon professionals, but the NRPP and AARST certifications are industry standard.
Sources & Methodology
Radon zone classifications for Nassau County are sourced from the EPA's Map of Radon Zones, which uses geological surveys, indoor radon measurements, and soil permeability data to assign each county a risk tier.
Disclaimer: Zone data represents county-level screening ranges and cannot predict the radon level in any specific home. Testing is the only reliable method to determine your home's radon concentration. This content is for informational purposes and is not medical advice.
Content review: Source-level retrieval dates
Editorial and Data Transparency
- Author
- RadonVerdict Data Team (Public Data and Cost Modeling)
- Content Review
- Source-level dates shown below
- Data Retrieved At
- 2026-02-24
Primary Sources
- EPA Map of Radon Zones (retrieved 2026-02-21)
- EPA A Citizen's Guide to Radon (retrieved 2026-05-05)
- CDC Environmental Public Health Tracking - Radon Testing (retrieved 2026-05-05)
- New York State Department of Health Residential Radon Test Data (retrieved 2026-05-05)
- Official NY radon program
- US Census Bureau, 2018-2022 American Community Survey 5-Year Estimates (retrieved 2026-02-24)