OSWER 9200.3-54  December 28, 2009 

EXTRACT: 
A number of foreign nations have evaluated the toxicity of dioxin and have established concentration 
values in soil that are intended to provide protection to humans who may be exposed under residential 
or commercial/industrial land uses. Two types of soil levels have been established: 
• 
Screening Levels are generally interpreted as concentrations below which health concern is 
minimal and no further investigations or evaluations are needed. 
• 
Action Levels are generally interpreted as concentrations above which concern is likely to exist 
and where some sort of response action is likely to be needed. 
Because dioxin is a carcinogen, the method used to derive screening levels or action levels depends 
on the assumed mode of action of dioxin. The World Health Organization (WHO) has evaluated the available 
data for dioxin, and has determined that cancer effects of dioxin are caused by a non-linear threshold 
mode of action. Consequently, human health will be protected from both cancer and non-cancer effects 
if