When conducting a human health risk assessment according to the U.S. EPA-OSW Human Health Risk Assessment Protocol (HHRAP), Chapter 4 of the protocol provides direction on evaluating ‘exposure scenarios’ in order to estimate the type and magnitude of human exposure to emissions from compounds of potential concern (COPC). These ‘exposure scenarios’ include adult and child farmers, residents, and fishers.
When analyzing residential areas near sources of COPCs, it can be difficult to know where the best location is for calculating risk of the exposure scenarios. Air dispersion modeling conducted in the area will produce maxima for multiple pathways – particle, particle-bound, vapor, and vapor mercury – for air concentration, dry deposition, and wet deposition; and these maxima can occur at unique calculation grid nodes.
To aid in identification of maximum air modeling parameters, Lakes Environmental’s IRAP-h View contains the Receptor Identification Polygon tool.
To Define the Highest Modeled Air Parameters:
Select the Risk Receptor Identification tool located in the Application Toolbar.
Click on the drawing area where you want to locate the first polygon corner.
Move the cursor to the location of the second corner and click again. Do this until you have digitized all the polygon corners. To close the polygon, click inside the small square surrounding the initial polygon corner, or click the right mouse button.
When you finish defining your polygon, the Risk Receptor Identification Polygon dialog is displayed.
Example Receptor Identification Polygon
The Risk Receptor Identification Polygon dialog consists of two tabs:
Geometry: Allows you to preview, specify, and edit the parameters of your polygon
Maximums: Allows you to place risk receptors at the locations of the highest modeled air parameters within the polygon.
For each maximum air parameter, you can select which exposure scenarios to apply at that location by selecting the appropriate column. Once selected, IRAP-h View will place markers at the identified Risk Receptors and conduct risk calculations for the appropriate exposure scenarios at these locations.