How can I derive a site-specific geometric standard deviation (GSD)?
In general, the Technical Review Workgroup for Metals and Asbestos (TRW) does not recommend that site-specific estimates of the GSD be attempted. This parameter is particularly difficult to evaluate at a site, as it is demanding with regard to the amount and quality of the data and the potential complications in the analysis. Unless there are substantial differences in child behavior and lead biokinetics at your site, the default GSD should be used (since it is based on national averages). Thus, site-specific GSD values should not be needed (see the Guidance Manual for the IEUBK, EPA 1994, page 4-25, Section 4.2.2 available for download from the Guidance page). In particular, the TRW recommends that site-specific estimates of GSD not be substituted for the default value without detailed, scientifically defensible studies documenting site-specific differences in child behavior or lead biokinetics (see the IEUBKwin User’s Guide, page 38, Section 2.2.8 available for download from the Soft
