Uranium and radon in private bedrock well water in Maine: geospatial analysis at two scales.

In greater Augusta of central Maine, 53 out of 1093 (4.8%) private bedrock well water samples from 1534 km(2) contained [U] >30 µg/L, the U.S. Environmental Protection Agency's (EPA) Maximum Contaminant Level (MCL) for drinking water; and 226 out of 786 (29%) samples from 1135 km(2) showed [Rn] >4,000 pCi/L (148 Bq/L), the U.S. EPA's Alternative MCL. Groundwater pH, calcite dissolution and redox condition are factors controlling the distribution of groundwater U but not Rn due to their divergent chemical and hydrological properties. Groundwater U is associated with incompatible elements (S, As, Mo, F, and Cs) in water samples within granitic intrusions. Elevated [U] and [Rn] are located within 5-10 km distance of granitic intrusions but do not show correlations with metamorphism at intermediate scales (10(0)-10(1) km). This spatial association is confirmed by a high-density sampling (n = 331, 5-40 samples per km(2)) at local scales (≤10(-1) km) and the statewide sampling (n = 5857, 1 sample per 16 km(2)) at regional scales (10(2)-10(3) km). Wells located within 5 km of granitic intrusions are at risk of containing high levels of [U] and [Rn]. Approximately 48 800-63 900 and 324 000 people in Maine are estimated at risk of exposure to U (>30 µg/L) and Rn (>4000 pCi/L) in well water, respectively.

Analyzing spatial and temporal (222)Rn trends in Maine.

Prolonged radon exposure has been linked to lung cancer. Cancer registry data indicates excess risk for age-adjusted lung cancer in Maine. Maine's mean residential radon activity exceeds the EPA maximum contaminant level (MCL). This paper describes the application of spatial autocorrelation methods to retrospective data as a means of analyzing radon activity in Maine. Retrospective air and well water radon activity data, sampled throughout Maine between 1993 and 2008, are standardized and geocoded for analysis. Three spatial autocorrelation algorithms-local Getis-Ord, local Moran, and spatial scan statistic-are used to identify spatial, temporal, and spatiotemporal radon activity clusters and/or outliers. Spatial clusters of high air- and well water-Rn activity are associated with Maine's Lucerne and Sebago granitic formations. Spatial clusters of low air- and well water-Rn activity are associated with Biddeford Granite and the metamorphic bedrock formation Silurian Ordovician Vassalboro. Space-time analysis indicates that most spatial clusters persist over the period of sampling. No significant temporal clusters are identified. Persistent spatial variations in radon may help to better understand and predict radon-related health risks associated with Maine residences.

Spatial variation of waterborne radon and temporal variation of radon in water at nine Maine schools.

Nine elementary schools in Maine were examined to track the release of 222Rn and to determine the transfer coefficient from water into air. Water-use simulations were performed by running sinks and sprayers for 1 h in a kitchen. The 222Rn in air was measured over 24 h throughout the school. The subsequent release of 222Rn into the kitchen air was measured to be greater than the EPA action level of 0.15 Bq L-1 (4 pCi L-1), but negligible concentrations of 222Rn were found in adjacent classrooms. In two schools, more than 10 222Rn-in-air detectors were placed throughout the kitchen and showed a three-fold spatial concentration variation. During the hour-long simulations, the 222Rn in water concentration was measured periodically, and many of the schools showed an increase in the 222Rn concentration in water before remaining constant. These measured variations suggest that multiple detectors are needed to accurately measure waterborne 222Rn in air, and multiple delayed measurements of 222Rn dissolved in water are needed to obtain a representative groundwater sample.

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.

Waterborne radon in seven Maine schools.

This study investigated the transfer coefficient of radon from water to air in kitchens and bathrooms for seven schools located in Maine. Simulations occurred in water use rooms containing multiple airborne radon detectors. Quantities measured included radon concentration in water (10-960 Bq L(-1), 260-26,000 pCi L(-1)), air (0-3 Bq L(-1), 0-80 pCi L(-1)), volume of water used, emissivities (0.04-0.98), and ventilation rates (0.012-0.066 min). Using these parameters provides the means for calculating the transfer coefficient and by which dose due to waterborne radon can be estimated in other schools. Transfer coefficient values calculated for kitchens and baths ranged from 9.6 x 10(-6) to 2.0 x 10(-2). Multiple detectors showed that the radon concentration varied throughout a room. These measurements represent the first of this type to be done in schools in Maine.