CO 



cr 

 o 



s 



3 



u 



z 



HI 



o 



UJ 



LOW-CXDSE 



REGION OF 



CONCERN 



\^ 



DOSE OF CARCINOGEN 



OBSERVED DATA POINTS 



• CHEMICAL A 

 ▲ CHEMICAL B 

 ■ CHEMICAL C 



MODELS 



Low dose 

 extrapolation 



Models fit within 

 observed data range 



i 



Ol 

 UJ 



u. u- 



olti 



Z X 



UJ O 



o 



UJ 



cc 



Rfd 



Frequercy - 



RfD- 



UF- 

 NOAEL- 



Dose- 



Propcnion of 

 animals tested 



Reference Dose 



Uncertainty Factor 



No Observed 

 Adverse Effects 

 Level 



Ingested Dose 



DOSE OF NONCARCINOGEN 



Figure 2 Hypothetical example of dose-response curves for a 

 carcinogen and a noncarcinogen. 



