# APPENDIX B: SUMMARY OF REVISIONS TO

LEAD UPTAKE BIOKINETIC MODEL

SOFTWARE VERSIONS

B-1TABLE B-1.SUMMARY OF REVISIONS TO LEAD UPTAKE/BIOKINETICMODEL SOFTWARE FROM LEAD 0.2 TO LEAD 0.4ItemLead 0.2 (September, 1989)Lead 0.4 (September, 1990)GI-tract absorption modelDefault is linear "passive" model.Default is non-linear "active-passive" modelDrinking water defaultsComposite = 9 μg/LComposite = 4 μg/LFirst flush = 0 μg/LFirst flush = 4 μg/LFlushed = 9 μg/LFlushed = 1 μg/LFountain = 0 μg/LFountain = 10 μg/L% First flush = 0% First flush = 50% Flushed = 0% Flushed = 35%% Fountain = 0% Fountain = 15%(New defaults were provided EPA/ODW)Diet defaultsDietary lead intakes are based on FDADietary lead intakes are based on FDA surveys completed in 1988.Default values range fromsurveys completed in 1986.Default values5.8-7.5 μg/day for ages 0-7.range from 22-34 μg/day for ages 0-7.Probability density functionP(x) = (1/(2.51)(GSD))¡P(x) = (1/(2.51)(x)(lnGSD))¡ exp((-1/2)((lnx-lnGM)/ lnGSD)2)exp((-1/2)((lnx-lnGM)/ lnGS D)2)Plot of probability density functionOrdinate of "Bell-shaped plot" labelledOrdinate of "bell-shaped plot" labelled "probability density function f(blood lead)" numbers removed"probability".from ordinate.Probability is computed as the integral of this function over a specified ranged.Thisis graphically illustrated in the "S-shaped" probability percent plot.Calculation of blood lead in newbornFixed at 6.4 μg/dL:User option:1) As in Lead 0.2 and option to select maternal blood lead.2) "Fetal" model, in(BPbn)BPbn=BPbm ¡ k, wherewhich maternal blood lead is calculated based on user-defined exposure data and a maternalBPbm is the maternal bloodbiokinetic model, and newborn blood lead is calculated from biokinetic model.lead (7.5 μg/dL) and k is aconstant (0.85).Soil/Dust primary data entry screenMenu includes "Change GI AbsorptionMenu revised to "Change GI Method/Bioavailability".If "yes" is selected, a window containing theMethod"following message appears over the secondary data entry screen:"Bioavailability of soil lead mayvary depending on the lead source.For example, lead from mine wastes may have a lowerbioavailability than lead from smelters.Differences in bioavailability are thought to reflectdifferences in gastrointestinal absorption of specific lead species and particle sizes, which varydepending on the source.The following data entry screen allows the user to make adjustments inthe gastrointestinal absorption coefficients to account for site-specific information on bioavailability.



# B-2TABLE B-2.SUMMARY OF REVISIONS TO LEAD UPTAKE BIOKINETIC MODEL SOFTWAREFROM LEAD 0.4 TO LEAD 0.5Parameter or FeatureLead 0.4 (September, 1990)Lead 0.5 (December, 1990)(Non-linear GI Absorption ModelVolume of GI-tract calculated,Volume of GI-tract calculated, VGI=(VGI)(GF).Default value for Km, 100 mg/L.VGI = (VGI)/(GF); where VGI is theadult GI-tract volume (liters) and GF isthe age-dependent allometric scalingfactor (GF < 1 for children).Defaultvalue for Km, 100 μg/L.Age Range SelectionMenu specified selection.User designated option allows user to specify any designed age range from 1-7 years.Multiple RunsMultiple model runs are made manually;Allows user to input a range of lead values for one medium (air, diet, drinking water, dust ori.e., the user specifies input for each run,soil), and make a series of model runs in which lead levels in the specified medium are variedand saves output in Results Out file.over the specified range.X-axis ScalingSet by program.Allows user to set scaling of X-axis of probability density function and probability percent graphsmanually.Overlay Graph FilesNot available; graphs of individual modelAllows user to save graph output (i.e., probability density function or probability percent graphs)runs can be displayed and/or printed.from multiple runs to an file and print output of multiple runs on a single graph.Text FilesData from individual model runs can beAllows user to save the data output of individual or multiple model runs, in user specified ASCIsaved to a file.text files; these files can be reviewed and printed in Lead and/or imported into a word orprocessing program after exiting from Lead.Blood vs. Media Concentration:ModelNot available.Allows user to input a range of lead values for one primary medium (air, diet, drinking water,Runs (Graph Output)dust or soil), and produce a series of model runs in which lead levels in the specified medium arevaried over the specified range.The output of each run is captured in an X-Y plot of mean bloodlead vs. medium lead.Blood vs. Media Concentration:FindNot available.Calculates a lead level in the user-specified medium that is associated with a specified mean bloodlead.



# B-3TABLE B-3.SUMMARY OF REVISIONS TO LEAD UPTAKE BIOKINETIC MODEL SOFTWAREFROM LEAD 0.5 TO LEAD 0.99dParameter or FeatureLead 0.5 (December, 1990)Lead 0.99d (January, 1994)Batch Mode Model RunsNot available.Accepts a properly formatted ASCII text file (*.DAT) containing data on lead exposure and blood leadlevels for a sample population, and calculates predicted blood lead levels for each individual.The outputis saved as a *.TXT file that can be viewed within Lead or imported into a text editor (e.g., wordprocessor), and as a *.ASC file that can be imported into PBSTAT for selected statistical analysis andgraphic display.PBSTATNot available.Accepts the output of batch mode operations (i.e., *.ASC files) and delivers statistical and graphic outputselected by the user from a menu.PBSTAT can be accessed from the main menu of Lead, or externallywith a DOS command (PBSTAT).The printer options in PBSTAT are the same as those in PBPLOT.PBPLOTNot available.Produces graph prints from Lead.It is accessed with a DOS command (PBPLOT).PBPLOT performsthe same functions as "Graphics Selection Menu" in Lead, however, it produces graph prints at muchhigher resolutions (e.g. HP Plotter and PostScript printer graphs).PBPLOT accepts *.LAY and *.PBMfiles produced with Lead.Main MenuRestructured.Model Iteration PeriodOne month with no user option.One day with user option."Fetal" ModelMaternal blood lead is calculated basedNot available.on user-defined exposure data and amaternal biokinetic model, andnewborn blood lead (BPbn) iscalculated from a biokinetic model.Soil IntakeDefault value is 100 mg/day for allDefault values are:ages.agesoil intake(yr)(mg/day)0-1851-21352-31353-41354-51005-6906-785View/Print Data FileUser must exit Lead and import *.TXTAllows the user to view and print *.TXT data files within Lead.data files into a text editor (e.g., wordprocessor) to view or print data.



# B-4TABLE B-3 (cont'd).SUMMARY OF REVISIONS TO LEAD UPTAKE BIOKINETIC MODEL SOFTWAREFROM LEAD 0.5 TO LEAD 0.99dParameter or FeatureLead 0.5 (December, 1990)Lead 0.99d (January, 1994)Contribution of soil lead to indoor dust leadDefault value function is 0.28 μg Pb/gDefault value function is 0.70 μg Pb/g dust per μg Pb/g of soil.dust per μg Pb/g of soil.Outdoor air lead concentrationDefault value is 0.2 μg/m3.Default value is 0.1 μg/m3.Dietary lead intakeDefault values were based on aDefault values are based on a more detailed analysis of FDA 1988-90 data.preliminary analysis of 1988 FDA surveydata.Editing of default biokinetic parametersCoding error resulted in changes toCoding error corrected.RECSUM time constants (e.g., TPLUR)not being accepted, as a result the UBMappeared to be insensitive to changes inTPLUR.Euler AlgorithmForward Euler algorithm calculates theBackward Euler algorithm calculates the increase compartmental lead mass over the iterationincrease compartmental lead mass overinterval as the total lead inflow to the compartment, minus the total lead outflow at the end of thethe iteration interval as the total leadinterval.inflow to the compartment, minus the totallead outflow at the beginning of theinterval.Tissue Pb and Excretory TransferRevised.CoefficientsNon-linear GI Absorption Model"Non-integrated" approach:Saturable"Integrated" approach:Intakes from all media are considered in the calculation of the saturableabsorption coefficients are calculated forabsorption coefficients for each medium (via SATURATION(t).each medium (soil, diet, drinking water,etc.) based on intakes from each medium,and are used to calculate media-specificuptakes which are summed to yield totaluptakes.



# B-5