Gas phase concentration in the soil layer and aqueous phase concentration in the ground water layer are passed to CalTOX, a Multimedia Total Exposure Model for Hazardous Waste Sites produced by the California EPA, Department of Toxic Substances Control. (See http://www.cwo.com/~herd1/caltox.htm for more details.)
Under control of SELECT, the CalTOX Excel Spreadsheet, is executed once for each time period in the transport simulation and returns three quantities for each time period--population exposure through the inhalation, ingestion and dermal pathways.
These three exposures, along with a total value, are plotted versus time by SELECT.
Clicking the "Comparative Exposures" button on the Exposure graph displays a table of comparative data ranking possible carcinogenic hazards from various exposures to the contaminant being simulated that might occur in ways other than inhabitation of the contaminated site.
Clicking the "Modify Assumptions" button on the Exposure graph permits modifications of CalTOX input parameters in the areas of human exposure, landscape properties and chemical properties.
Upon clicking "Recalculate Exposures," new exposure curves can be produced and various "what-if" scenarios played out.
Another capability of SELECT is to allow the user to move the population (the residential site) to other locations in or near the contaminated site. By simply clicking on and moving the house icon in the site characterization window, the user can quickly generate another profile of environmental concentrations (soil gas, ground water) and exposures. Since all the information from a transport simulation is available, this type of "what-if" analysis is done without again running the transport simulation.