**2. Categories of AhR-ligands**

There are two major categories of AhR-ligands: exogenous and endogenous ligands. Exogenous ligands are those that are synthetic (formed as a result of nonbiological activity) and/or naturally occurring dietary AhR-ligands. Endogenous ligands are those formed in biological systems as a result of natural processes in the body [7].

### **2.1 Exogenous AhR-ligands**
