A National Comparison Between the Collocated Short- and Long-term Radon Measurements in the United States

BACKGROUND: Knowing the geographical and temporal variation in radon concentrations is essential for assessing residential exposure to radon, the leading cause of lung cancer in never-smokers in the United States. Tens of millions of short-term radon measurements, which normally last 2 to 4 days, have been conducted during the past decades. However, these massive short-term measurements have not been commonly used in exposure assessment because of the conflicting evidence regarding their correlation with long-term measurements, the gold standard of assessing long-term radon exposure. OBJECTIVE: We aim to evaluate the extent to which a long-term radon measurement can be predicted by a collocated short-term radon measurement under different conditions. METHODS: We compiled a national dataset of 2,245 pairs of collocated short- and long-term measurements, analyzed the predictability of long-term measurements with stratified linear regression and bootstrapping resampling. RESULTS: We found that the extent to which a long-term measurement can be predicted by the collocated short-term measurement was a joint function of two factors: the temporal difference in starting dates between two measurements and the length of the long-term measurement. Short-term measurements, jointly with other factors, could explain up to 79% (0.95 Confidence Interval [CI]: 0.73 to 0.84) of the variance in seasonal radon concentrations and could explain up to 67% (0.95 CI: 0.52 to 0.81) of the variance in annual radon concentrations. The large proportions of variance explained suggests that short-term measurement can be used as convenient proxy for seasonal radon concentrations. Accurate annual radon estimation entails averaging multiple short-term measurements in different seasons. SIGNIFICANCE: Our findings will facilitate the usage of abundant short-term radon measurements, which have been obtained but was previously underutilized in assessing residential radon exposure.