All TCDD and TCDF were assumed to exhibit the same degree of toxicity and carcinogenicity as the 2, 3, 7, 8 Isomer of TCDO 2. The toxicity and carcinogenicity of 2, 3, 7, 8 TCDF equals that of 2, 3, 7, 8 TCDD 3. The sensitivity of humans to the health effects of these materials equals that of the most sensitive species observed 1n lab studies 4.