Assessment of living level indoor radon in detached single-family homes in the coastal plains town of Freehold, New Jersey

Indoor radon levels are influenced by underlying geology, ventilation rates, indoor environments, building structure, and many other variables that must be taken into account when predicting where the highest levels may occur. To uncover which factors have the greatest influence in Freehold, New Jersey, alpha track detectors were exposed in 125 detached dwellings for three months. Houses in Freehold were found to have indoor radon levels with a geometric mean of 2.8 pCi/L which is well above the national aver average of 1 pci/L. Statistical tests determined that the factors that most contribute to high indoor radon levels in Freehold are the age of the house (radon levels increase with house age) and the extent of conditioning in the basement (radon levels are higher in houses with air conditioned basements). The best way to predict whether a house in Freehold has high indoor radon is to determine the house's age, because radon levels are clearly higher in houses at least 25 years old.