Description:

The Stochastic Human Exposure and Dose Simulation model for Air Toxics (SHEDS-AirToxics) is a multimedia, multipathway population-based exposure and dose model for air toxics developed by the US EPA's National Exposure Research Laboratory (NERL). SHEDS-AirToxics uses a probabilistic approach to estimate distributions of air toxic exposure and dose for a user-specified population based on air toxic concentrations supplied as input to the model. SHEDS-AirToxics provides estimates of the range in air toxic exposure and dose across a population (variability), and the percent of the simulated population exposed to different levels. The stochastic basis for the model also allows for the uncertainty in any given percentile of the exposure or dose distribution to be estimated.

Record Details:

Record Type:MODEL

Product Published Date:01/21/2004

Record Last Revised:07/11/2011

Record ID: 75915

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Model Detail:

Model Evaluation :At this time, only conceptual, mathematical, and chemical/physical verification has been performed by model developers.

Model Guidance Documents :Not currently available.

Model Download Information :Not currently available for download.

modelcontactinfo :Dr. Stephen Graham
US EPA ORD
National Exposure Research Laboratory
graham.stephen@epa.gov
(919)-541-4344

Dr. Janet Burke
US EPA ORD
National Exposure Research Laboratory
burke.janet@epa.gov
(919) 541-0820

Model Inputs :User must supply hourly ambient outdoor air toxic concentrations for the population of interest (either monitoring data or output from an air quality dispersion model can be used).

Additional input databases provided with the model include: US Census 2000 demographic data that are used to generate individuals that demographically represent the user-specified population; human time-location-activity data from EPA's Consolidated Human Activity Database (CHAD) assigned to each simulated individual to account for the microenvironments people spend time in; US FDA's Total Dietary Study (TDS) food residue data and USDA's Continuing Survey of Food Intakes by Individuals (CSFII) food consumption survey data used for estimating dietary exposure.

Distributions for the parameters of equations used to estimate microenvironmental air toxic concentrations based on the ambient outdoor air toxic concentration (i.e. mass balance equation parameters such as penetration and air exchange rates) are input by the user through the GUI screens.

Smoking prevalence data is required to be input through the GUI if exposure to environmental tobacco smoke is included in the model run scenario. Traffic volume data and HAP usage information (e.g. refueling frequency) are also required for estimating inside vehicle and refueling exposures, respectively.

Model Outputs :Model outputs include of air toxic exposure and dose distributions (daily average and annual average) for the user-specified population. Other output options include individual annual exposure and dose time profiles, summary statistics tables, and contributions of exposure and dose by route (inhalation, dietary ingestion, dermal contact).

Model Computer Requirements:

Model Operating Systems Needs :Microsoft Windows operating system, (Windows 98, 2000, or XP)

Model Hardware Needs :A minimum of 128 MB RAM, 300 MHz processor, 800MB free disk space for program and database files, and a CD-ROM drive; however, 512 MB RAM, 1.8 GHz processor, and 1.0GB free disk space is recommended for optimal model performance.

Model Programming Language(s) :SAS version 8.2 for PC including BASE, STAT, and GRAPH

other_req :Graphical user interface (GUI) allows for user specification of the model run scenario and input data, as well as for analysis and display of model outputs.