1. Select Scenario

Choose one of the 7 landuse scenarios and then select which media to assess under the "Select Media:" list that is displayed (except for "Fish" and "Soil to Groundwater").

2. Select Screening Level Type

Select the type of screening level (SL) desired. If "Site Specific" is selected go to Step 3. If "Defaults" is selected go to step 5.

3. Select Chemical Info Type

The "Select Chemical Info Type" drop down menu will appear. Select either "Database hierarchy defaults" or "User-provided". "Database hierarchy defaults" uses the toxicity values and the chemical-specific parameters as selected by the hierarchies described in sections 2.3 and 2.4 of the User's Guide, respectively. "User-provided" gives the option to change toxicity values and chemical-specific parameters in step 7.

4. Select RfD/RfC Type

Select either "Chronic" or "Subchronic" types of RfD and RfC values. As a general rule of thumb, EPA considers an exposure duration of more than 7 years to be chronic. Shorter durations may be considered subchronic. In some instances some risk assessors will consider a shorter exposure duration to still be chronic if the exposures occur frequently. If you are working on a Superfund site, we recommend you contact a toxicologist or risk assessor in the EPA Regional Superfund Program for your site. Chronic and Subchronic toxicity values are selected according to the hierarchy presented in section 2.3 of the User's Guide.

5. Select Individual Chemicals

Select one or more contaminants for SL calculation. Select a contaminant by highlighting it in the left box and click the ">>" button to move it to the box on the right. Contaminants in the box on the right will be used for SL calculation. Highlight multiple contaminants at once by using the "Shift" key. Remove a contaminant from the right box by highlighting it and clicking the "<<" button. You may choose all contaminants by checking the "ALL" box. The calculator run time will correspond with the number of contaminants selected.

6. Click Retrieve

Click the "Retrieve" button at the bottom of the page. If "Default" SLs are being calculated go to step 9. If "Site Specific" SLs are being calculated go to step 8.

7. Site-specific Parameters

Enter site-specific toxicity values, chemical-specific parameters and exposure parameters. Click the "Retrieve" button at the bottom of the page.

If you have consulted with the community around a Superfund site and agreed to exposure scenarios or exposure assumptions which differ from the default values initially identified on the RSL website, you can change those in the calculator. If changing any of these inputs it is important to review which media (e.g. soil, air, groundwater) you want to change. Note that changing toxicity values or risk levels for one media, does not automatically change the other media. If you are working on an actual or potential Superfund site, we recommend discussing the use of non-default inputs with a toxicologist or risk assessor in the EPA Regional Office Superfund Program for you site. If you are using RSLs on a Superfund site, consider placing a hard copy in the Administrative Record for your Superfund site decision.

8. View Results

Review your results. In order to save a copy of your input parameters and SL results choose from the following options:

• Click "Output to Spreadsheet" to save in spreadsheet (.xls) format
• Click "Output to PDF" to save in PDF (.pdf) format
• Select "Print" from the File Menu or press CTRL+P to print from your browser.

Once this has been done, you will have a preliminary record of your calculations, including all of the inputs and screening levels. You now have a dated record of your site-specific RSLs, including the inputs. If you are using RSLs on a Superfund site, consider placing a hard copy in the Administrative Record for your Superfund site decision.