CHAPTER 6

Non- and Mono-ortho Chlorinated Biphenyls

N. Kannan

Polychlorinated biphenyls (PCBs) are a complex mixture, identified in every component of the global ecosystem. If potential toxicity, environmental prevalence, and potential risk to humans and wildlife are considered, non- and mono-ortho substituted chlorinated biphenyls become extremely important. They resemble 2,3,7,8-tetrachloro dibenzo-p-dioxin (TCDD) in their biological action, causing hepato-, immuno-, reproductive, and dermal toxicities, and inducing mixed function oxidase (MFO) enzymes. This is the basis behind TCDD toxic equivalency (TEQs) as an approach towards risk assessment. Improvements in chromato-graphic techniques have yielded an array of analytical methods for these congeners that resulted in the determination of coplanar non-ortho and mono-ortho CBs in air, water, soil, and in organisms. Long range trans-hemispheric transportation of these substances in air and ocean currents have been demonstrated. Their contents in commercial PCBs have been studied and their formation during incineration is shown. Long term studies in river sediments demonstrate reductive dechlorination. PCB clearance from animals occurs both by non-metabolic and metabolic routes. Their flux in air, water, and sediments is estimated. OH reactions in the atmosphere is proposed as a principal source of loss along with permanent burial in marine and fresh water sediments.

Keywords. Non-orrto, Mono-ortho, Coplanar, PCBs, Review

1 Introduction...............................128
2 Biological Effects and the Concept of 2,3,7,8-TCDD Toxic Equivalency ....132
3 Biotransformation............................ 135
4 Ecoepidemiology ............................ 136
5 Congener-Specific Analysis....................... 137
6 Source and Formation.......................... 140
7 Global Occurrence, Transportation, and Fate.............140
7.1 Air, Water, and Sediment ........................140
7.2 Aquatic Organisms............................143
7.2.1 Invertebrates ...............................143
7.2.2 Fish ....................................145
7.2.3 Aquatic Mammals ............................145
7.3 Birds....................................146
7.4 Humans..................................148
8 Time Trend................................149
9 PCB Transformation and Removal...................150
References....................................151