Recommendations regarding specific contaminants of concern are 

 beyond the scope of this guidance manual. A general list of con- 

 taminants with available EPA toxicological data listed in IRIS is 

 provided in Appendix B. The procedures for quantitative risk assess- 

 ment outlined in this manual are designed for use only with chemicals 

 having toxicological indices [Reference Doses (RID) or Carcinogenic 

 Potency Factors). In addition to the availability of toxicological in- 

 dices, the relative bioaccumulation potential of various chemicals is a 

 key consideration in selecting contaminants of concern. EPA priority- 

 pollutant organic chemicals and selected pesticides are listed in Table 

 1 in descending order of bioaccumulation potential, according to their 

 octanol-water partition coefficients (Tetra Tech 1985a). Note that 



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