Encyclopedia of Environmental Science and Engineering, Volume I and II

PCBs AND ASSOCIATED AROMATICS 895

Tables 27 and 28 show the calculated daily intake of

PCDDs and PCDFs from foods. The values used for the

daily intake of different types of food were derived from

“Nutrition Survey Data, Japanese Agency of Health and

Welfare, Daiichi Press, Tokyo, 1982” as reported by Y.

Takizawa and H. Muto^72.

Table 29 compares the ratio of PCDD : PCDF isomers

found in both the calculated values from foods and the

observed ratios in human tissues.

There seems to be a good correlation between the dietary

intake of PCDDs and PCDFs and the amounts found in each

of the tissue types except for octachlorinated isomers. The

reason for this may be that the source of O 8 CDDs in tis-

sues may be other than food. The best correlation is found

between the penta-hepta isomers. Since there are a large

number of factors which have not been considered in these

tables, such as obesity and pharmacokinetics, it is somewhat

surprising that the correlations are as good as they are.

People in industrialized countries have an adipose

tissue level of PCDDs of about 1000–1200 ppt whereas

people in non-industrialized countries have much lower

levels. PCDF levels in industrialized countries are not

usually below 50 ppt.

The estimation of health risk to humans was initially

based on the amount of 2,3,7,8-TCDD/F present. In order to

better estimate the risk caused by exposure to a mixture of

different PCDD and PCDF isomers the concept of “TCDD

Equivalents” have been introduced. Several models have

TABLE 25

Aroclor 1016 contains 0.4% by weight of PCBs with more

than 4 Cl substituents

PCB isomer Weight % PCDF isomers

produced by pyrolysis

2,3,4,3
,5
 0.16 1,2,3,6,8-

2,4,6,7-

2,3,6,2
,3
, 0.01 1,2,8,9-

1,2,6,9-

1,4,6-

2,3,6,3
,5
 0.01 2,4,6,9-

1,2,6,8-

2,3,6,2
,5
 0.18 1,2,6,9-

1,4,6,9-

1,2,8-

1,4,8-

2,4,6,2
,3
 0.04 1,2,7,9-

1,3,8,9-

1,3,6-

2,4,3
,4
 0.14 1,3,7,8-

2,4,5,4
 1.35 1,3,4,7-

2,4,2
,4
 1.81 1,3,7,9-

2,3,2
,3
 0.18 1,2,8,9-

2,3,4,2
 2.00 1,2,3,9-

2,3,2
,5
 1.14 1,2,6,9-

2,4,2
,5
 3.48 1,3,6,9-

2,4,5,2
 1.41 1,3,4,9-

2,3,2
,6
 0.33 triCDFs

2,3,5,2
 0.47 1,2,4,9-

2,3,2
,6
 0.33 triCDFs

2,3,5,2
 0.47 1,2,4,9-

2,4,6,4
 2.40 triCDFs

2,5,2
,5
 4.35 1,4,6,9-

2,5,2
,6
 1.07 triCDFs

2,3,6,2 1.00 triCDFs

2,6,2
,6
 0.19 triCDFs

C016_003_r03.indd 895C016_003_r03.indd 895 11/18/2005 1:12:37 PM11/18/2005 1:12:37 PM