New Hampshire’s radon exposures exceed the national average due to the geology of the state and its granite bedrock. Among homes with elevated radon, the average concentration varied by county, ranging from 6.0-9.1 pCi/L. Values above 100 pCi/L have been reported in every county in New Hampshire. Another route of exposure comes from radon concentrations present in private water wells.
As part of its outreach and education mission, the New Hampshire Radon Program has created a story map showing the relationship between indoor radon testing results and estimated levels of radon in groundwater in towns across New Hampshire.
The map features a side-by-side comparison map with a sliding arrow to reveal the results of air and water radon levels in comparison.
By sliding the arrow to the right, indoor air radon testing results are shown by town. The darkest blue color indicates towns where 45% or more of the tested homes have radon at or above the EPA action level of 4 pCi/L.
By sliding the arrow to the left, the probability of radon in groundwater over 2,000 pCi/L is shown. Areas shaded in warm colors (red to orange) have the highest chance of elevated radon in groundwater.
New Hampshire Radon Program notes the advisory level for radon concentrations in well water is 2,000 pCi/L if air radon concentrations in the home exceed 4 pCi/L. Recommendations concerning radon water concentrations are:
The New Hampshire Department of Health and Human Services (NH DHHS) and New Hampshire Department of Environmental Services (NHDES) recommend that homeowners with private wells with radon concentrations at or above 10,000 pCi/L install treatment for the water in conjunction with mitigation of indoor air radon. For private wells with radon concentrations between 2,000 and 10,000 pCi/L, the treatment of water is recommended if air concentrations in the home exceed 4 pCi/L.
See the map at https://storymaps.arcgis.com/stories/9ae32c5f346f459188fa676f8d9eef44
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