Charles E. Chrosniak

Reliability of inexpensive charcoal and alpha-track radon monitors

A comparison between single short-term radon measurements and annual radon measurements in basements shows that significant uncertainties should be associated with the short-term measurements. Activated charcoal radon monitors which measure radon over a 3 to 7 day interval yield measurements that should carry a ± 90% uncertainty in terms of estimating annual radon concentration. Alpha-track radon monitors which measure radon over a 3 month interval should carry a ± 30% uncertainty. Decisions about home purchases, home remediation and the development of risk characterizations may often be incorrect if currently popular but unrealistically low estimates of uncertainty are applied to short-term radon measurements. Optimal results are obtained from year-long alpha-track measurements.

Soil radon, permeability, and indoor radon prediction

Attempts to predict which geographic areas should be associated with a high percentage of homes with unusually high indoor radon levels have been based on estimates of soil radon and soil permeability for geological units. In northern Virginia and southern Maryland, it appears that predictions of indoor radon based on estimates of homesite soil radon and soil permeability are very useful.

Radioactive hazard of potable water in Virginia and Maryland

Only a few studies have examined instances of prolonged exposure to radionuclide concentrations found in natural settings. Radium in domestic water in Florida counties has been correlated with a higher than normal incidence of leukemia. A similar study in Iowa towns reported on a correlation between radium and increases in lung, bladder and breast cancer. Radium and radon in domestic water has been correlated with the development of lung cancer in a study of several Texas counties. A correlation has been found between radon in home water supplies in Maine and the incidence of lung cancer. Starting in the winter of 1986-87, the Center of Basic and Applied Science conducted a study of indoor radon and soil radon. Most of the study homes are in Fairfax County in northern Virginia, and the immediately adjacent Montgomery County in southern Maryland. Approximately 650 homeowners agreed to participate in the radon-in-water study. The study group now includes approximately 1,400 people, over 1,000 of whom have consumed their present water supply for 5 or more years, and over 700 of whom have consumed this water for 10 or more years.

Prediction of indoor radon by aeroradioactivity

Attempts to predict which geographic areas should be associated with a high percentage of homes with unusually high indoor radon levels in Virginia and Maryland have been based on estimates of soil radon and soil permeability for geological units. This method is found to be less successful and probably less cost-effective than the use of total-gamma aeroradioactivity maps.

Indoor radon and well water radon in Virginia and Maryland

The domestic use of radioactive water has long been a cause for concern, but only a few studies have examined prolonged exposure to radionuclide concentrations found in natural settings. This paper reports on the indoor radon concentrations from 1,500 homes in northern Virginia and southern Maryland and well water radon from 700 homes in the same area. Indoor radon concentrations are almost all between 1 and about 40 pCi/L. The winter season shows the highest values with about 40% of the homes over the US EPA action level of 4.0 pCi/L. The summer season shows the lowest values with about 25% of the homes over this level. This seasonal variation is related to home ventilation. Waterborne radon in homes with private well ranges from about 100 pCi/L to about 8,000 pCi/L. In small homes, indoor radon can be significantly increased by outgassing of the home water supply, even at water radon levels of less than 10,000 pCi/L.

Statistical analysis of the radon-222 potential of rocks in Virginia, U.S.A.

More than 3,200 indoor radon-222 (222Rn) measurements were made seasonally in an area of about 1,000 square kilometers of the Coastal Plain and Piedmont physiographic provinces in Virginia, U.S.A. Results of these measurements indicate that some geological units are associated, on the average, with twice as much indoor222Rn as other geological units, and that indoor222Rn varies seasonally. The Kruskal-Wallis test was used to test whether indoor222Rn concentrations for data gathered over the winter and summer seasons differ significantly by rock unit. The tests concluded that indoor222Rn concentrations for different rock units were not equal at the 5-percent significance level. The rocks associated with the highest median indoor222Rn concentration are specific rocks in the Mesozoic Culpeper basin, including shale and siltstone units with Jurassic diabase intrusives, and mica schists in the Piedmont physiographic province. The pre-Triassic Peters Creek Schist has the highest ranking in terms of indoor222Rn concentration. The rocks associated with the lowest indoor222Rn concentrations include coastal plain sediments, the Occoquan Granite, Falls Church Tonalite, Piney Branch Mafic and Ultramafic complex, and unnamed mafic and ultramafic inclusions, respectively. The rocks have been ranked according to observed222Rn concentration by transforming the average rank of indoor222Rn concentrations to z scores.

Development of Radon Enrichment in Soil Gas over Quartz-Mica Schist in Virginia

A major portion of northern Virginia is underlain by a quartz-muscovite soil, on average about 10 meters thick, that has developed on a bedrock of polymetamoirphic schist. The schist formed from an ancient clay-rich sediment eventually recrystallized several times, as the modern Appalachian rocks were heated deep in the Earth and subsequently exposed by erosion. The total gamma radioactivity and the permeability of the schist are higher than average, and combine to generate a radon-rich soil-gas that can be brought into homes by the pressure differential normally present in local homes that commonly are well insulated and have basements. More than half of the homes, based on three-month measurements, exceed the U.S. Environmental Protection Agency recommended maximum for indoor radon of 4 pCi/L. Fortunately, while the area is experiencing a rapid inc rease in new home construction, it is possible to avoid types of home construction susceptible to, and areas of, high soil-gas radon and high permeability.