The tenfold "uncertainty" factor traditionally used to guard against human interindividual differences in susceptibility to toxicity is not based on human observations. To begin to build a basis for quantifying an important component of overall variability in susceptibility to toxicity, a data base has been constructed of individual measurements of key pharmacokinetic parameters for specific substances (mostly drugs) in groups of at least five healthy adults. 72 of the 101 data sets studied were positively skewed, indicating that the distributions are generally closer to expectations for log-normal distributions than for normal distributions. Measurements of interindividual variability in elimination half-lives, maximal blood concentrations, and AUC (area under the curve of blood concentration by time) have median values of log10 geometric standard deviations in the range of 0.11-0.145. For the median chemical, therefore, a tenfold difference in these pharmacokinetic parameters would correspond to 7-9 standard deviations in populations of normal healthy adults. For one relatively lipophilic chemical, however, interindividual variability in maximal blood concentration and AUC was 0.4--implying that a tenfold difference would correspond to only about 2.5 standard deviations for those parameters in the human population. The parameters studied to date are only components of overall susceptibility to toxic agents, and do not include contributions from variability in exposure- and response-determining parameters. The current study also implicitly excludes most human interindividual variability from age and illness. When these other sources of variability are included in an overall analysis of variability in susceptibility, it is likely that a tenfold difference will correspond to fewer standard deviations in the overall population, and correspondingly greater numbers of people at risk of toxicity.

No abstract

and organizat have had joint-funding (cooperative) agreements of streamflow records since 1896, and for 1937. Organizations that assisted in collecti data through joint-funding agreements with the State Agencies: ons of the State of Georgia for the systematic collection other hydrologic records since ng and evaluating hydrologic Survey are:

Introduction 1 Basic mission and program 5 Addresses and telephone numbers of Georgia District and Field Headquarters 6 Summary of hydrologic conditions in Georgia, 1993 water year 7 Surface-water numbering system 7 Streamflow 7 Water quality 8 Water-quality profiles of the Chattahoochee River 8 Water-quality profiles of the Ocmulgee and Altamaha Rivers 11 Ground water 12 Water use 12 Georgia District Projects 13 Surface-water monitoring, GA001 14 Ground-water monitoring, GA002 15 Evaluation of the effects of urban storm runoff on the water quality of the Upper Floridan aquifer near an altered sinkhole, Albany, Georgia, GA00209 16 Geology and ground-water resources in the Zebulon area, Georgia, GA00210 17 Evaluation of hydrologeology and ground-water chemistry of the Upper Floridan aquifer near Albany, Georgia, GA00211 18 Quality-of-water monitoring, GA003 19 Sediment monitoring, GA004 20 Atmospheric deposition monitoring, GA005 21 Water use in Georgia, GA007 22 Statewide flood studies, GA059 23 Flood-frequency characteristics of urban streams in Georgia, GA062 24 Acid Rain, dry deposition, and terrestrial processes research at Panola Mountain State Park, Georgia, GA085 25 Movement and fate of agricultural chemicals in the surface and subsurface environments, southwestGeorgia, GA087 26 Effects of flood-detention reservoirs, Gwinnett County, Georgia, GA090 27 Hydrology of the Upper Floridan aquifer in the Albany, Georgia, area, an analysis from digital modeling, GA091 28 Development of State Geographic Information Systems to support environmental management activities in Georgia, GA092 29 Water-resource evaluation of the Glynn County, Georgia, area, GA093 30 Hydrology of the Valdosta, Georgia, area and effect of Withlacoochee River recharge on the Upper Floridan aquifer, GA095 31 Hydrogeology of Cumberland Island and the impact of ground-water withdrawals and channel deepening on the freshwater resources of the Island, GA096 32 Evaluation of the migration and fate of contaminants at an abandoned manufactured gas plant at Albany, Georgia, GA097 33 Assessment of the water resources of the Chatham County, Georgia, area, GA100 34 Use of chlorofluorocarbons to assess the contamination potential of a limestone aquifer in a karst terrane, GA101 35 National Water-Quality Assessment Program the Apalachicola-Chattahoochee-Flint River basin study, GA102 36 Water, energy, and biogeochemical budgets at the Panola Mountain Research watershed, GA103 37 in CONTENTS-ContinuedGeorgia District Projects Continued Ground-water flow and quality in the vicinity of the Savannah River at the Savannah River Site, Georgia and South Carolina, GA104 38 Quality of storm-water runoff in DeKalb County, Georgia, GA106 40 Reconnaissance evaluation of surface-and ground-water quality in the White and Mossy Creek watersheds, White County, Georgia, GA107 41 Assessment of air-pollutant loadings and resultant water-quality impacts in Stewart and Marion Counties, Georgia, GA108 42 Geostatistical evaluation of vadose-zone flow and transport processes, GA...

Open-File Report 88-515This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature. Any use of trade names is for descriptive purposes only and does not imply endorsement by the USGS.ACC is a registered trademark of Advanced Computer Communications. DEC, DECnet, Micro/RSX, PDP-11, Q-bus, RSX-11M, RSX-11M-Plus, UNIBUS, and VAX/VMS are trademarks of Digital Equipment Corporation.Although this program has been tested by the Geological Survey, United States Department of the Interior, no warranty, expressed or implied, is made by the Geological Survey as to the accuracy and functioning of the program and related program material, nor shall the fact of distribution constitute any such warranty, and no responsibility is assumed by the Geological Survey in connection therewith.