The data, scenarios, and models used to represent human exposures to radon in drinking water include at least four important relationships (i) The magnitude of the source-medium concentration, that is, the concentrations of radon in the water supply and in other relevant media, such as ambient air, (ii) the contaminant concentration ratio, which defines how much a source-medium concentration changes as a result of transfers, transformation, partitioning, dilution, and so on before human contact, (iii) the extent of human contact, which describes (often on a body-weight basis) the frequency (days per year) and magnitude (liters per day) of human contact with a potentially contaminated exposure medium (tap water, indoor air, or outdoor air), and (iv) the likelihood of a health effect, such as cancer, associated with a predicted extent of human contact. The latter area of uncertainty includes that of the dose-response model assumed. Uncertainties in modeling the movement of radon with the wall of the stomach (model structure), in the model parameters, and the lack of relevant experimental observations are the critical sources of uncertainty. The key points discussed included one overarching issue, that being how uncertainty and variability can affect the reliability of the estimates of health effects for any exposure scenario and related control strategies.

Mitigation of Radon in Air

There has been considerable research on and practical experience with the use of active (mechanical) systems for the control of radon entry into buildings. Use of such systems, when they are properly installed and operating, can typically yield indoor airborne radon concentrations below 150 Bq m-3 and can often result in concentrations of about 75 Bq m-3. Although there is considerable experience with the design and installation of active systems, monitoring programs are needed to ensure the continued successful operation of individual active systems. Another possible way to reduce risks associated with exposure to airborne radon is to design and build radon-resistant new buildings. Although the technical potential for building radon-resistant buildings has been demonstrated under some circumstances, the scientific basis for ensuring that it can be done reliably and as a consistent outcome of normal design and construction methods is inadequate. With the exception of the results in research conducted in Florida, there are no comparative data on which to base estimates of the overall effects of radon-resistant construction methods on reducing concentrations of radon in indoor air radon concentrations.

Mitigation of Radon in Water

Several water treatment technologies have been used to effectively remove radon from water. However various issues and secondary effects must be addressed in connection with each method, including intermedia pollution (transfer

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