Sandimirov S. Screening studies of POP levels in bottom sediments from selected lakes in the Paz watercourse / In State of the environment in the Norwegian, Finnish and Russian border area. The Finnish Environment. Finland, Jyvaskyla: Kopijyva Oy. 2007, №6.

Screening studies of PO P levels in bottom sediments from selected lakes in the Paz watercourse - 4 Concentration in sediments ng/g dry weight ■ SChlordanes Figure 6. Chlorinatedpesticide levels (ng/g dry weight) in surface (0-1 cm) bottom sediments, 2003­ 2005. Numbers above bars represent concentrations o f the contaminants. 5.4.2. Polychlorinated biphenyls Polychlorinated biphenyls (PCBs) are a family o f 209 synthetic compounds made up o f attached benzene rings with varying numbers and locations o f chlorine atoms. PCBs are characterized by their low flammability, low electrical conductivity, high resistance to thermal breakdown and to other chemical agents, and high degree o f chemical stability. These qualities make them effective coolants, lubricants, and insulators. However, the same properties that led to their extensive use in industry (mainly resistance to degradation and low volatility) also make them persistent environmental contaminants and a serious health threat to humans and wildlife. PCBs concentrate in the food web and bioaccumulate in the fatty tissues of animals and humans. Chronic low-level PCB exposures can cause liver damage, reproductive abnormalities, immune suppression, neurological and endocrine system disorders, retarded infant development, and stunted intellectual function. The International Agency for Research on Cancer ranks PCBs as a probable human carcinogen. Non-ortho and some mono-ortho CB congeners are the most toxic contaminants among all PCBs because they exert their toxic effect via the same mechanism as dioxins. Such PCBs are called dioxin-like PCBs. Rapport APN- 514.3665.01 16