Humans can be exposed to hazardous air pollutants (HAPs) either directly through inhalation or indirectly through ingestion or dermal contact, which can result in acute or chronic health effects. The risk of exposure varies depending on a number of variables, including the meteorological conditions, local geographical and emissions characteristics, the age of the individuals being exposed, and the exposure duration and frequency. To evaluate and quantify the potential health impacts that may result from specific exposure scenarios, human health risk assessments (HHRAs) are conducted.
There are a number of steps involved with conducting a HHRA. Modelers must first identify the chemicals of potential concern (COPC) as well as the emission rates and sources. The U.S. EPA Human Health Risk Assessment Protocol (HHRAP) can be used to identify the COPCs as this protocol provides methodology guidance, fate and transport, exposure and health risk algorithms for predicting the impacts of COPC released into the atmosphere from emission sources. The next step is to select the exposure scenarios, for which recommendations can also be found in the HHRAP, and then estimate the media concentrations, exposure, and risk. The movement of COPCs in the environment can be a complex process so modelers can use the AERMOD model to conduct the air dispersion modeling. Then, the AERMOD input and output files from the air dispersion modeling analysis, along with chemical-specific fate and transport variables, can be used as the necessary inputs for the media and exposure equations in the HHRAP which account for the movement of chemicals within and between media including air, soil, water, and sediment.
To streamline the HHRA process, BREEZE Software offers BREEZE AERMOD and BREEZE Risk Analyst, which modelers may use in combination to conduct their air dispersion modeling analyses and then seamlessly complete the risk assessment. BREEZE Risk Analyst is an add-in for Esri ArcGIS that is designed to perform human health risk assessment modeling by implementing the fate and transport equations from the HHRAP within the software and allowing for the seamless visualization of results. Additionally, Risk Analyst provides modelers with the ability to import source data from AERMOD input (.inp) files as well as modeled impacts from AERMOD plot (.plt) files, thereby streamlining and simplifying the HHRA process.
To learn how to import AERMOD input and output files into BREEZE Risk Analyst for your human health risk assessments, please follow the steps below:
After starting a New project in Risk Analyst, click Import on the Sources tab:
Browse to the desired folder location, and select individual or multiple *.inp files and click Open. (Note: Users can import all emission sources from one AERMOD input file, or from different AERMOD input files to one Risk Analyst file. However, keep in mind that if multiple AERMOD files are used, the coordinate system should be the same.)
Once the AERMOD input file(s) are imported, the sources will be displayed in the Source Data Tree. To view the source properties, simply click on the imported source name in the Source Data Tree.
Once the sources have been added, the next step is to import the AERMOD dispersion modeling results. To do this, click on Add Plotfiles in the Sources tab:
Browse to the desired folder location and select the desired *.plt file(s) to be imported.
Once the AERMOD plotfile(s) are imported, they will be displayed in the data tree under the Plotfiles folder. If they are not automatically placed, simply drag and drop each unassigned plotfile from the Plotfiles folder to the correct air modeling folder for the correct source and phase (i.e., vapor, particle, and particle-bound):
The last part of this process is plotfile parameter mapping. Click on the desired plotfile, and then click the + to expand the data tree. The Column and Units fields should now be visible. (Note: For definitions of the chv, cyv, dydv, and dywv parameters, refer to the user manual.)
The parameters can be successfully mapped by using one of two options:
Option 1: Click in the empty box next to the Column and select the desired parameter field from the dropdown list:
Option 2: First click in the box next to the Column field and then select the actual field heading in the plotfile view:
This process will need to be repeated until all AERMOD modeling parameters have been mapped.