Call us: (203) 272-3600

Cities With the Highest Radon Levels in Connecticut

Connecticut Flag

Radon testing is not always a priority, but in the state of Connecticut, 1 in 3 homes have elevated radon levels, according to the CT Post. Across the rest of the U.S., that number is only about 1 in 15 homes. Depending on which Connecticut city you live in, you may be at a dramatically elevated risk for exposure to this cancer-causing gas. 

Based on the geology and location, some cities throughout Connecticut have consistently exhibited elevated levels of radon:

  • Brookfield
  • Sherman
  • Greenwich
  • Stratford
  • Old Lyme
  • Ledyard

Keep reading to find out why these cities are considered higher risk for the presence of radon gas. You’ll also see whether you should make radon testing a priority, even if you don’t live in one of the counties listed. 

Connecticut Zones With the Highest Radon Risks

To start, it’s important to know why many of the Connecticut cities that have higher levels of radon seem to be located together. According to the Connecticut Department of Public Health, the four southernmost Connecticut counties have the highest risk for excessive radon (greater than 4 pCi/L). These counties include Middlesex, New Haven, Fairfield, and New London. 

The U.S. Geological Survey explains that uranium is the “parent element” to radon gas, meaning that this gas is the byproduct of the breakdown of its parent. Areas that show higher levels of radon gas likely have certain types of uranium-rich rocks in their underlying soil:

  • Dark shales
  • Various types of granite
  • Volcanic rocks that are light in color
  • Sedimentary rocks containing phosphate
  • Metamorphic rocks that derived from the rocks listed above

It’s possible that the Connecticut cities that show elevated levels of radon have an abundance of these uranium-laden rocks in their soil. Because radon may more easily escape from permeable soils, such as gravel and sand, that may also help explain why homes in the southernmost, ocean-side counties exhibit the highest levels of this dangerous gas. 


The town of Brookfield notes that several areas within its city limits have shown higher-than-normal levels of radon. With its location in Fairfield County, which was named a Radon Zone 1, it’s not surprising that this location features elevated levels of this gas. Like other cities with elevated radon levels, the city and state health departments have partnered to offer free testing kits to residents. However, it’s never a bad idea to play it safe and call in the professionals to conduct a thorough radon test on your home. 


With its location nearby Brookfield, it should come as little surprise that this city has also shown elevated levels of radon gas. These higher radon levels have been spotted in water tested from public-utility wells, placing Sherman on the list of cities that may pose an exposure risk. As a city located in Fairfield County, this city has an inherently higher risk of radon gas exposure due to its EPA rating of being a Radon Zone 1. 


Another Fairfield County community with elevated concentrations of radon is Greenwich. Due to the underlying geology of this coastal city, there is a strong chance that the presence of this gas may be an issue for residents. The Department of Health noted that the average indoor level of radon in Greenwich was measured at 4.5 pCi/L or more. This is above the EPA's threshold of 4.0 pCi/L. In fact, the same report also explains that radon levels in some sources of water in the city were found to be above 5,000 pCi/L, which is also above the state’s limits. 


Stratford is yet another Fairfield County town know to exhibit elevated radon levels. In fact, the New Haven Register explains that the high levels even pushed the town’s Health Department to begin marketing a health campaign aimed at encouraging residents to test their homes for this dangerous gas. The Town Health Director explains that the City of Stratford’s “geography and rock formations” make it one of the towns that have a higher percentage of homes with elevated radon levels. 

Old Lyme 

Old Lyme is located in the County of New London, one of Connecticut’s four counties that received an EPA assignment of Radon Zone 1. An article from the Hartford Courant explained that testing of the water from public-utility wells in Old Lyme contained some of the highest radon levels in the state. Once radon makes it into a source of water, it can be inhaled as steam during a shower or through drinking. 


The Hartford Courant also lists the city of Ledyard as a location with higher levels of radon. Again, this dangerous gas was found in many private and public-utility wells around the city. Ledyard is also located in New London County, which the EPA calls a Radon Zone 1.


The list of cities above with known levels of radon that exceed tolerable amounts is not exhaustive. You should not use this list to confirm you have elevated radon levels, nor should you assume you’re safe if your home isn’t on the list. 

Although these Connecticut cities are known to have some of the highest radon levels, it should be noted that elevated amounts can be found anywhere in the state. The region’s natural geology puts homeowners at risk no matter where they live. 

This naturally occurring gas can literally be found anywhere, and levels can dramatically fluctuate even among neighboring homes. Regardless of whether you live in any of the four Connecticut Counties designated as Zone 1 for radon risk or your city is near any of the ones listed above, it’s a wise move to check for this dangerous gas. Testing is too simple, the mitigation systems are too effective and the health risks are too great to justify not taking precautions.