bw Technical Evaluation of the Proposed “Screening” Level Using the Critical Organ Methodology and ICRP-26 J. W. Healy Los Alamos National Laboratory The EPA provides two screening levels, one for soil and one for air. We will discuss the soil screening level first then the air screening level and finally some perceived problems in the application of the EPA Guidance. A mass loading approach is used to define the resuspension leading to inhalation. The EPA first refers to a study by Anspaugh in which concentra- tion data for various radionuclides was compared with air concentrations. (Slide 1.) the dust. In this comparison he used an air concentration of 100 ug/m? for It may be noted that the agreement is good for resuspension data and covers a wide variety of areas. This method seems to be more a correlation using a fixed value of the mass loading in the air than a true mass loading approach. The EPA, however, seemed to be enamoured with some correction for particle size and derived the method for correcting for particle size in the soil and air given in the next slide (Slide 2) even though the Anspaugh correlation provided conservative results for the variety of areas included. It should be noted that the EPA approach requires considerable additional measurements on size fractions in the soil and air. Although they claim that representative areas could be used, they do not indicate how these are selected nor how many are required so that a true estimate of the increased costs cannot be made. However, it is important to note that this method has never been tested to prove its applicability to estimating resuspension. The assumptions used in calculating the soil -l-