Residential neighborhood in Alpharetta GA where radon levels average 4.9 pCi/L

Radon Levels in Alpharetta, GA

Average: 4.9 pCi/L | EPA Zone 1 | Above the EPA Action Level

Alpharetta has some of the highest radon levels in Metro Atlanta. Here's what the data shows and what it means for your home.

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4.9

pCi/L Average

Above EPA action level of 4.0

Zone 1

EPA Classification

Highest radon risk category

3.8x

National Average

National avg is 1.3 pCi/L

Understanding Alpharetta's Radon Levels

Alpharetta's average indoor radon level of 4.9 pCi/L places it above the EPA's recommended action level of 4.0 pCi/L. This is not a number that should cause panic, but it does mean that testing your specific home is important rather than optional.

An average of 4.9 pCi/L means the distribution of radon levels across Alpharetta homes is spread widely. Some homes test below 2.0 pCi/L with minimal risk. Others test at 8, 10, or even 15+ pCi/L, where health risks become more significant. Your neighbor's test result tells you nothing about your own home because radon entry depends on the specific geology beneath your foundation, your home's construction, and even small differences in soil permeability.

The only way to know where your home falls on this spectrum is to test. A professional test takes 48 hours with zero disruption to your daily life.

What Your Test Results Mean

Below 2.0 pCi/LLow Risk

Below average. No immediate action needed, but the EPA notes there is no safe level of radon exposure. Consider retesting every 2-5 years.

2.0 - 3.9 pCi/LModerate Risk

The EPA recommends considering mitigation at this range. The World Health Organization recommends action at 2.7 pCi/L. Retest to confirm.

4.0 - 7.9 pCi/LHigh Risk

At or above the EPA action level. Mitigation is strongly recommended. Many Alpharetta homes fall in this range given the 4.9 pCi/L average.

8.0+ pCi/LVery High Risk

Well above the EPA action level. Prioritize mitigation. Equivalent lung cancer risk of smoking half a pack of cigarettes per day. Some Alpharetta homes test in this range.

Alpharetta vs. Neighboring Cities

How radon levels in Alpharetta compare to other North Fulton and nearby cities:

City	County	Avg Radon	EPA Zone	Risk
Alpharetta	Fulton	4.9 pCi/L	Zone 1	High
Milton	Fulton	5.2 pCi/L	Zone 1	High
Roswell	Fulton	4.2 pCi/L	Zone 1	High
Johns Creek	Fulton	4.6 pCi/L	Zone 1	High
Cumming	Forsyth	3.8 pCi/L	Zone 2	Moderate
Sandy Springs	Fulton	3.5 pCi/L	Zone 1	Moderate

Average levels based on available testing data. Individual homes vary significantly. Always test your specific home.

What Affects Radon Levels in Alpharetta

Piedmont Granite Bedrock

Alpharetta sits on the Piedmont geologic province, characterized by granite and gneiss formations. These rocks contain trace amounts of uranium that decay into radon gas. The granite below North Fulton is the primary source of elevated radon.

Foundation Type

Slab-on-grade homes (common in newer Alpharetta subdivisions) and crawl space homes (common in older areas) allow radon entry through different pathways. Cracks, joints, and gaps in any foundation type create entry points for soil gas.

Seasonal Variation

Radon levels in Alpharetta homes tend to be highest in winter months (November through March) when homes are sealed tighter and the temperature difference between indoors and outdoors increases the stack effect, drawing more soil gas inside.

Home Age and Construction

Both old and new Alpharetta homes test positive for elevated radon. Newer energy-efficient homes can sometimes trap more radon due to tighter building envelopes. Older homes may have more foundation cracks but better natural ventilation.

Seasonal Radon Variation in North Fulton

Radon levels in Alpharetta homes are not constant throughout the year. Understanding seasonal patterns helps you interpret your test results and plan retesting:

Winter (November - March)

Typically 20-40% higher radon readings due to:

Homes sealed tighter, less natural ventilation
Greater temperature differential increases stack effect
Heating systems create negative pressure at foundation
Frozen or saturated ground can redirect soil gas

Summer (April - October)

Typically lower readings, but not always safe:

Open windows increase natural ventilation
Smaller temperature differential reduces stack effect
AC can still create negative pressure in some homes
Heavy rain can increase soil gas pressure temporarily

Testing tip: You can test for radon any time of year in Alpharetta. Winter tests may show a worst-case scenario, while summer tests may understate the risk. The EPA recommends retesting every 2 years regardless of when you last tested.

Alpharetta Radon Level FAQs

What is the average radon level in Alpharetta, GA?

The average radon level in Alpharetta is approximately 4.9 pCi/L, which is above the EPA action level of 4.0 pCi/L. This makes Alpharetta one of the higher-radon areas in Metro Atlanta. Individual homes can vary significantly, with some testing below 2.0 and others above 10.0 pCi/L.

Why is Alpharetta's radon level higher than other Atlanta suburbs?

Alpharetta sits on dense Piedmont granite formations in North Fulton County. The specific geological composition of the bedrock in this area contains higher concentrations of uranium-bearing minerals, which decay into radon. The closer you get to the Blue Ridge foothills, the higher radon levels tend to be.

What EPA radon zone is Alpharetta in?

Alpharetta is in EPA Radon Zone 1, the highest risk classification. Zone 1 areas have a predicted average indoor radon level above 4.0 pCi/L. The entire North Fulton corridor (Alpharetta, Milton, Roswell, Johns Creek) is Zone 1.

Are radon levels higher in winter in Alpharetta?

Yes. Radon levels in Alpharetta homes are typically 20-40% higher during winter months compared to summer. This is caused by the stack effect: warm indoor air rises, creating negative pressure at the foundation level that draws radon-laden soil gas into the home. Homes are also sealed tighter in winter, reducing natural ventilation.

Does a 4.9 pCi/L average mean every home in Alpharetta is high?

No. The average is a statistical measure across many homes. Some Alpharetta homes test below 2.0 pCi/L while others test above 10.0 pCi/L. Radon levels can vary dramatically even between neighboring homes due to differences in soil composition, foundation condition, and home construction. Testing is the only way to know your specific level.

How does Alpharetta compare to the national average?

The national average indoor radon level is approximately 1.3 pCi/L. Alpharetta's average of 4.9 pCi/L is nearly four times higher than the national average and above the EPA action level. This places Alpharetta well above most of the country for radon risk.

What radon level requires mitigation?

The EPA recommends mitigation for any home testing at 4.0 pCi/L or above. The EPA also states that radon levels between 2.0 and 4.0 pCi/L should be considered for mitigation. The World Health Organization recommends action at 2.7 pCi/L. There is no known safe level of radon exposure.

Can radon levels change over time in my Alpharetta home?

Yes. Radon levels fluctuate based on season, weather, soil moisture, barometric pressure, and changes to your home (renovations, HVAC modifications, foundation settling). The EPA recommends retesting your home every 2 years, even if previous results were low. Homes should also be retested after major renovations.