MONTE-CARLO MODELING OF CHILDHOOD LEAD-EXPOSURE - DEVELOPMENT OF A PROBABILISTIC METHODOLOGY FOR USE WITH THE USEPA IEUBK MODEL FOR LEAD INCHILDREN

An integrated stochastic exposure (ISE) model using microexposure tech niques was developed to characterize short-term variability and uncert ainty in residential childhood lead exposure at the census tract level . The ISE model was linked to the biokinetic module of the United Stat es Environmental Protection Agency (USEPA) IEUBK Model for Lead in Chi ldren (v. 0.99D) to predict the distribution of blood lead concentrati ons (PbB). We demonstrate an application of the ISE model using probab ility distributions to characterize variability and uncertainty in age -specific physiology and activity patterns, demographics and housing c onditions, concentrations of lead in multiple environmental media, and media-specific uptake rates. Output from the ISE/IEUBK model was comp ared with output from the IEUBK Model using central tendency point est imates for exposure variables and an assumed geometric standard deviat ion (GSD). Results of sensitivity analyses suggest that key exposure v ariables include percent lead in paint, dust lead concentration, and s oil and dust ingestion rate; however, the relative importance of each input variable depends on (1) a child's age, (2) the percentile of the PbB distribution, and (3) the time step used to simulate intraindivid ual variability in parameter values.