Polychlorinated biphenyls (PCBs) are a class of organic compounds with 1 to 10 chlorine atoms attached to biphenyl. Theoretically there are 209 different congeners of PCB, of which 130 different are found in environmentally samples.
PCBs were widely used for example as dielectric fluids in transformers and capacitors and coolants. Due to the toxicity of PCBs and their classification as persistent organic pollutants, PCB production was banned in the United States in 1976 and in other western nations during the 1980’s. The toxicity of PCBs varies considerably among congeners. The coplanar PCBs (known as non-ortho PCBs because they are not substituted at the ring positions ortho next to the other ring), i.e. PCBs 77, 126, 169, tend to have dioxin-like properties, and generally are among the most toxic congeners.
PCBs make up the majority of persistent organic pollutants in all seabird species. The PCB levels are 5-50 times higher than hexachlorobenzene and 2-7 times higher than DDT. The glaucous gull and great black-backed gull had significantly higher liver concentrations of ΣPCB than the other seabird species. There were no regional differences in PCB concentrations within the Barents Sea. According to large reports from AMAP the PCB levels in Arctic are lower than from more temporal and populated areas. The time trend series from the Barents Sea also points downward, for example was the ΣPCB levels 80% higher in 1983 than in 2003 in herring gull, black-legged kittiwake and Atlantic puffin eggs.