A laboratory intercomparison of radon in water measurements in Maine

Naturally occurring radon exists in ground water and drinking water supplies. Many water testing laboratories provide measurements of radon in water for the public. No known national intercomparison program exists to verify the accuracy of the laboratories measuring radon in water in Maine or the Northeast. In recognition of this situation, the State of Maine Radiation Control Program sanctioned an intercomparison study for laboratories registered in Maine to measure radon in water. The University of Maine supplied each laboratory with water samples of various radon concentrations, served as the reference laboratory, and analyzed the results. Of the nine participating laboratories, eight use the liquid scintillation method while the ninth uses the E-PERM method to measure radon in water. Presented here are the results of this intercomparison study with a tabulation of the materials and methods used by the laboratories. The results from five of the nine testing laboratories showed significant discrepancies with those of the reference laboratory, typically due to low measurements.