Jump to main content.


CREM Logo

Model Report

Stochastic Human Exposure and Dose Simulation for Particulate Matter

Last Revision Date: 07/11/2011 View as PDF
General Information Back to Top
Model Abbreviated Name:

SHEDS-PM
Model Extended Name:

Stochastic Human Exposure and Dose Simulation for Particulate Matter
Model Overview/Abstract:
The Stochastic Human Exposure and Dose Simulation for Particulate Matter (SHEDS-PM) Version 2.0 is a population exposure and dose model for particulate matter developed by the US EPA's National Exposure Research Laboratory (NERL). EPA SHEDS-PM 2.0 uses a probabilistic approach to estimate distributions of PM exposure and dose for a user-specified population based on PM concentrations supplied as input to the model. SHEDS-PM 2.0 provides estimates of the range in PM exposure and dose across a population (variability), and the likelihood of exposures above a particular level. The stochastic basis for the model also allows for the uncertainty in any given percentile of the exposure or dose distribution to be estimated.
Keywords:
Model Technical Contact Information:
Janet Burke
US EPA ORD
National Exposure Research Laboratory
burke.janet@epa.gov
(919) 541-0820

User Information Back to Top
Technical Requirements
Computer Hardware
Program and related files require approx. 100MB of disk space. Input databases provided with the program code require 400MB of disk space. A minimum of 256 MB of RAM is recommended for optimal model performance.
Compatible Operating Systems
Microsoft Windows operating system, (Windows 98, 2000, or XP)
Other Software Required to Run the Model
Microsoft Access is used as the input database interface for the SHEDS-PM model. All of the three required input databases are provided with the model as Microsoft Access databases. The user must enter the PM concentration data to be used in the model run into a template Microsoft Access database table provided with the model that is set up in the required format. Instructions are provided on how to add PM concentration data to the template file in the required format. The user is not required to have Microsoft Access on the computer that runs the model; a properly formatted PM concentration database located in a directory accessible to the computer is sufficient.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.
Download Information
Not currently available for download.
Using the Model
Basic Model Inputs
User must supply ambient outdoor PM concentrations for the population of interest (either monitoring data or output from an air quality dispersion model can be used). Different formats for the PM concentration data are acceptable, such as 24-hour average concentrations or hourly concentration values.

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, and human activity pattern data from EPA?s Consolidated Human Activity Database (CHAD) are assigned to each simulated individual to account for the different microenvironments people spend time in.

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

Smoking prevalence data are required to be input through the GUI if exposure to environmental tobacco smoke is included in the model run scenario.

Basic Model Outputs
Model outputs include distributions of PM exposure and dose for the user-specified population. Total exposure and dose estimates, as well as the contributions from outdoor and indoor sources of PM to the total are available as output. Also output are exposure and dose estimates due to time spent in the various microenvir-onments for each of the above outputs. Time series profiles of PM exposure and dose for simulated individuals can also be output from the model.
User Support
User's Guide Available?
User's manual is available.

Model Science Back to Top
Problem Identification
SHEDS-PM 2.0 uses a probabilistic approach to estimate distributions of PM exposure and dose for a user-specified population based on PM concentrations supplied as input to the model. SHEDS-PM 2.0 provides estimates of the range in PM exposure and dose across a population (variability), and the likelihood of exposures above a particular level. The stochastic basis for the model also allows for the uncertainty in any given percentile of the exposure or dose distribution to be estimated.
Summary of Model Structure and Methods
SHEDS-PM 2.0 simulates the time series of PM exposure and dose for demographically representative individuals through random assignment of human activity pattern data from CHAD to each simulated individual. PM concentrations in the indoor locations where people spend time (such as home, work, or school) are calculated using equations that depend on the outdoor PM concentration, and can also account for indoor PM sources. Each simulated individual's time series of exposure is then calculated from the time spent in each location (indoors, outdoors, in a vehicle) and the PM concentration in that location. Activity-specific inhalation rates while in each location are also calculated by the model and combined with the exposure concentrations to estimate an intake-dose profile for each individual. Daily-averaged values are calculated from the daily exposure and dose profiles, and then combined to provide distributions for the user-defined population.
Model Evaluation
Currently undergoing beta-testing and model evaluation.


Local Navigation


Jump to main content.