Formation of PCDDs and PCDFs by the chlorination of water

Two samples of tab water and double distilled water were chlorinated using chlorine gas. A series of PCDFs could be identified from these experiments, however no PCDDs could be found. The two water samples gave very similar isomeric patterns ( . . tetra-CDFs), however the congener profile (Cl₄ --- Cl₈) was different. These experiments indicate that all products formed by chlorination reactions are potentially contaminated by PCDFs by a specific “chlorine pattern”.     

Inhibition of ethoxyresorufin-O-deethylase (EROD) activity in mixtures of 2,3,7,8-tetrachlorodibenzo-p-dioxin and polychlorinated biphenyls

Induction of ethoxyresorufin-O-deethylase (EROD) activity and porphyrin accumulation shows different structure-activity relationships for different polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Interactions between the two responses can strongly influence the induction and activity of EROD. The results support the conclusion that there are nonadditive interactions between nondioxin-like PCBs and dioxin-like compounds. The interaction between EROD activity and the porphyrin biosynthesis makes the prerequisite of additivity in the toxic equivalency factor concept for environmental mixtures highly spurious. Inhibition of EROD activity caused by non-dioxin like compounds could have a significant impact on the value of EROD activity as a biomarker in the present methods of risk assessment for these compounds.     

Absorption of polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans by breast-fed infants

The absorption of polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans was studied in four breast-fed infants. The absorption was measured by comparing the estimated total intake and the excretion in faeces, during 48 hours, at three different time points; 1, 2 and 3 months post parta. The levels of the analysed compounds in the human milk are typical for Sweden, i.e 20 ppt toxic equivalents for the dibenzo-p-dioxins and dibenzofurans and for the polychlorinated biphenyls 16 ppt toxic equivalents. For most of the congeners the absorption is found to be over 95%. Higher excretion is noticed for heptachlorinated and octachlorinated dioxins.