Medical Geology Post on Environmental Radon
General radon levels in the environment can vary greatly, depending on locale and the medium it is measured in. Here are comparisons between indoor/outdoor air, soil air and groundwater.
Conversion factors below are from the picoCurie / liter to the Becquerel / m^3:
1 picoCurie / liter = ~ 37.1 Bq/m^3 EPA action limit 4 pCi/L = ~ 148.4 Bq/m^3
Radon: Outdoor air Low of 4 – 8 Bq / m^3 = 0.2 – 0.3 picoCuries/liter
High of 100 Bq / m^3 in valleys (morning time) = 2.7 picoCuries / liter
Radon: Indoor air Low 20 Bq / ^3 = 0.5 pCi/l
High of 110000 Bq / m^3 = 2964 pCi/l (probably over a uranium mine)
World average 39 Bq / m^3 = 1.1 pCi/l
EXAMPLE INDOOR RADON LEVELS by Country: Average
Egypt: 9 = 0.2 pCi/l
UK: 20 = 0.5 pCi/l
USA: 46 = 1.5 pCi/l Texas 48 = 1.3 pCi/l
United States by Region: (geometric mean values) 3.43 pCi/L in the Northeast 2.36 pCi/L in Midwest, 0.64 in the Northwest, 2.40 pCi/L in the Mountain States, 1.43 pCi/L in the Southeast
Sweden: 108 = 2.9 pCi/l
Czech Republic: 108 = 2.9 pCi/l
Highest ever radon concentration ever reported in an indoor dwelling: 2600 pCi/L in a southeastern Pennsylvania home which is equal to a 4 pack a day smoker.
Radon in soil air: Ranges from less than 1 to over 2500 Bq / liter = 0.03 – 67.4 pCi/l
Most soils in the USA are between 5 – 55 Bq/liter = 0.13 – 1.48 pCi/l
Radon in groundwater: 3 – 80000 Bq/liter = 0.081 – 2156 pCi/l