POLYCHLORINATED BIPHENYLS (PCB's) - Environmental Implications

TOXICOLOGICAL EFFECTS OF PCB's ON HUMAN BEINGS

PCB's can reach to human being through bio-transfer route and may accumulate in fatty tissues. PCB's are inhaled in small amounts through the air or ingested through food. People are primarily exposed to PCB's by consuming fish from contaminated water, but they can also be exposed through other foods.

Since, PCB's are lipophilic, they are preferentially stored in adipose tissue. They are also present to a smaller extent in serum, organs and tissues and human milk. The concentrations of PCB's in the different organs depend on the lipid content of such organs, with the exception of the brain, where the concentration is lower. PCB's to a certain extent pass through the placenta. They are primarily excreted through bile and milk.

Yusho Accident, 1968 and Yu-Cheng Accidents 1980 are two unfortunate examples of effects of short and long term exposure of PCB's to humans.


Within few hours of acute exposure to PCB's, skin rashes may occur. Exposure through ingestion is possible in the working environment through direct ingestion alongwith hand and contaminated food. Skin exposure is important in the case of long term exposure, even though the ambient concentration may be low.
Table 8 PCB Congeners Important from Human Health viewpoint
 

BZ Number

IUPAC Nomenclature

A.            Known to cause direct toxicity

 

PCB-BZ 77

3,3’,4,4’-Tetrachlorobiphenyl

 

PCB-BZ 126

3,3’,4,4’,5-Pentachlorobiphenyl

 

PCB-BZ 169

3,3’,4,4’,5,5’-Hexachlorobiphenyl

B.            Stimulate the production of bio-activate enzyme

 

PCB-BZ 105

2,3,3’,4,4’,-Pentachlorobiphenyl

 

PCB-BZ 118

2,3’,4,4’,5-Pentachlorobiphenyl

 

PCB-BZ 128

2,2’,3,3’,4,4’-Hexachlorobiphenyl

 

PCB-BZ 138

2,2’,3,4,4’,5’-Hexachlorobiphenyl

 

PCB-BZ 156

2,3,3’,4,4’,5-Hexachlorobiphenyl

 

PCB-BZ 170

2,2’,3,3’,4,4’,5-Heptachlorobiphenyl

C.            Frequently found at high concentration levels in environmental samples or animal tissue

 

PCB-BZ 18

2,2’,5-Trichlorobiphenyl

 

PCB-BZ 44

2,2’,3,5’-Tetrachlorobiphenyl

 

PCB-BZ 49

2,2’,4,5’-Tetrachlorobiphenyl

 

PCB-BZ 52

2,2’,5,5’,-Tetrachlorobiphenyl

 

PCB-BZ 70

2,3’,4’,5-Tetrachlorobiphenyl

 

PCB-BZ 74

2,4,4’,5-Tetrachlorobiphenyl

 

PCB-BZ 151

2,2’,3,5,5’,6-Hexachlorobiphenyl

 

PCB-BZ 177

2,2’,3,3’,4’,5,6-Heptachlorobiphenyl

 

PCB-BZ 187

2,2’,3,4’,5,5’,6-Heptachlorobiphenyl

 

PCB-BZ 207

2,2’,3,3’,4,4’,5,6,6’-Nonachlorobiphenyl

D.            Mixed type inducers found at low concentration in tissues

 

PCB-BZ 37

3,4,4’-Trichlorobiphenyl

 

PCB-BZ 81

3,4,4’,5-Tetrachlorobiphenyl

 

PCB-BZ 114

2,3,4,4’,5-Pentachlorobiphenyl

 

PCB-BZ 119

2,3’,4,4’,6-Pentachlorobiphenyl

 

PCB-BZ 123

2’,3,4,4’,5-Pentachlorobiphenyl

 

PCB-BZ 157

2,3,3’,4,4’,5’-Hexachlorobiphenyl

 

PCB-BZ 158

2,3,3’,4,4’,6-Hexachlorobiphenyl

 

PCB-BZ 167

2,3’,4,4’,5,5’-Hexachlorobiphenyl

 

PCB-BZ 168

2,3’,4,4’,5’,6-Hexachlorobiphenyl

 

PCB-BZ 189

2,3,3’,4,4’,5,5’-Heptachlorobiphenyl