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 pgTEQ/g dw 5 - 4 - 3 - 2 - 1 - 0 - T E Q p c d d / f Figure 11. TCDD toxic equivalent (TEQPCDD/F) (pgTEQ/g dry weight) calculatedfo r PCDDs and PCDFs in bottom sediments from the Arctic lakes in 1996 (Skotvold et al. 1997) and 2003-2005 (reported data). 6. Toxicity of contaminant mixture In mixture together with others contaminants, some OCs can cause additive effects, others antagonize, and others synergistic responses (de March et al., 1998). Non-ortho (IUPAC nos. 77, 81, 126 and 169) and some mono-ortho CBs (IUPAC nos. 105, 114, 118, 123, 156, 157, 167 and 189) are stereochemically similar to 2,3,7,8 tetrachlorodibenzo-p-dioxin (2378-TCDD) and exert their toxic effect via the same mechanism as 2378-TCDD. Such PCBs are known as dioxin-like PCBs. Effect o f a mixture o f dioxin-like PCBs, and TCDD/F seems to be additive (de March et al., 1978). Individual toxicity o f both PCDD/Fs and dioxin-like PCB congeners in relation to the most toxic 2378-TCDD can be calculated using toxic equivalency factors TEFs (NATO/CCMS, 1988; Ahlborg et al., 1994). Recent studies have shown that some polycyclic aromatic hydrocarbons (PAHs) exert dioxin-like activity, being aryl hydrocarbon receptor (AhR) agonist and potent inducers o f EROD activity. This has facilitated the development o f 2378-TCDD- related TEFs for these PAHs (TEFPAH) (Willet et al., 1997; Clemons et al., 1998; Klimm et al., 1999). Applying o f the TEF values and the individual congener concentrations allowed calculation of total TCDD-equivalent toxicity (Total TEQ) for a mixture o f PCDD/Fs, PCBs, and PAHs and evaluation of contributions o f each o f them to Total TEQ. The developed absolute TEFPAH values are differerent (Table 9 ). Rapport APN- 514.3665.01 25