Encyclopedia of Environmental Science and Engineering, Volume I and II

PCBs AND ASSOCIATED AROMATICS 893

TABLE 23

PCDF toxicity decreases with decreasing lateral Cl substituents

PCDF Induction potency AHH Receptor binding affinity

2,3,4,7,8-PeCDF 2.6  10 ^10 1.5  10 ^8

1,2,3, 7,8-PeCDF 2.5  10 ^9 7.5  10 ^7

1,3,4, 7,8-PeCDF 1.6  10 ^8 2.0  10 ^7

1,2,3,7,9-PeCDF 9.0  10 ^8 4.0  10 ^7

2,3,4,7,9-PeCDF 7.9  10 ^9 2.0  10 ^7

1,2,4,7,8-PeCDF 1.1  10 ^7 1.3  10 ^6

2,3,4,7-TCDF 1.8  10 ^8 2.5  10 ^8

2,3,4,8-TCDF 4.1  10-8 2.0  10-7

1,2,3,7-TCDF 2.7  10-5 1.1  10-7

2700

2600

2500

2400

2300

2200

2100

2000

1900

1800

1700

1600

1500

0.0 0.5 1.0 1.5 2.0 2.5

Residence Time (sec)

Temperature (F)

Tetrachlorobenzene

Pentachlorobiphenyl

Mean residence time

Fast-path residence time

Temperature-Time Characteristics of Incineration

Incineration Requirements for 6-9’s DRE

FIGURE 40 The area above the curves shows the temperature-time correlation needed for 99.9999% DRE.

only amount to the conversion of a total of 5.7% of the PCB

present. The quantity of active PCDF isomers which could

be generated is extremely low and, typically, conversion

from PCB to PCDF takes place under optimum pyrolysis

conditions only to the extent of 4% and usually much less.

The conversion factor for the yield of slightly biologically

active PCDF isomers derived from Aroclor 1016 is therefore

a maximum of 0.002, that is, a PCDF : PCB ratio of 1 : 450.

Not only is the relative ratio of PCDFs : PCBs one half of

the 1 : 200 typical of Yusho and Yu-Cheng oils but, in addi-

tion, none of the toxic PCDF isomers found in the Yusho and

Yu-Cheng incidents could possibly be present when Aroclor

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