The slope factors for benzene are actually ranges, yet the SL table shows only a single number. Which number was chosen and why?
The upper end of the slope factor range was chosen. This is because the SL Table is a screening tool, and the consequences of screening out a chemical that could pose a significant risk are more serious than the consequences of carrying the chemical through to the next step of the risk assessment. (At each step of the risk assessment, the risk is further refined using site-specific analysis. Chemicals can always be eliminated from the risk assessment at a later step than the initial screening, if appropriate.) • What toxicity values are used for TCE? TCE currently has no EPA consensus toxicity value, and multiple estimates of TCE risk may be appropriate. Consult your regional risk assessor to determine whether your region or state has recommended TCE values. The toxicity hierarchy discussed in this FAQ was followed and the resulting toxicity values, except for the RfC, for TCE are from the California Environmental Protection Agency/Office of Environmental Health Hazard Assessment’s tox
The upper end of the slope factor range was chosen. This is because the SL Table is a screening tool, and the consequences of screening out a chemical that could pose a significant risk are more serious than the consequences of carrying the chemical through to the next step of the risk assessment. (At each step of the risk assessment, the risk is further refined using site-specific analysis.
Related Questions
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- The slope factors for benzene are actually ranges, yet the SL table shows only a single number. Which number was chosen and why?
- For manganese, IRIS shows an oral RfD of 0.14 mg/kg-day, but the SL Table uses 0.024 mg/kg-day. Why?
