Experimental Assessment of the Short- and Long-Term Effects of ²²²Rn from Domestic Shower Water on the Dose Burden Incurred in Normally Occupied Homes

Abstract

Previous studies of the effects of 222Rn in drinking water have centered on the long-term or chronic exposure to 222Rn and its decay products. In this study, the possible effects that the transient increase caused by the release of 222Rn from shower water can have on the 222Rn concentration have been studied. In addition, the increment in the lung dose incurred by the occupants of a normally occupied home and the long-term increase in the 222Rn concentration and the associated dose in the home has also been examined. Various parameters are of interest including the release of the 222Rn from the shower water, the role of ventilation as a removal mechanism, and the behavior of the aerosol present in the home. Experimental work was performed in a shower stall constructed in the laboratory and in a bathroom in a normally occupied home. The home was supplied with water containing around 550 kBq m-3 of 222Rn. A transfer coefficient around 0.70 and equi librium factors up to 0.69 were measured in the laboratory. The ventilation rates measured in the home were in agree ment with those found in the literature, 0.5−4.0 h-1. The dose incurred was assessed using the lung dose model developed by the International Commission on Radiological Protection (ICRP). Calculations indicated that for homes with 222Rn in the domestic water similar to the experimental home, the short-term exposure during showering could contribute a 17% increase in dose over the average daily dose. However, the increase in the long-term average concentration caused by the release of 222Rn from water use in the home could more than double the average daily dose. Thus, the focus of concern regarding radon in domestic water should be primarily on its effects on the long-term airborne 222Rn concentration.