By-side impurities in chloronaphthalene mixtures of the Halowax series: all 75 chlorodibenzo-p-dioxins

A by-side chlorodibenzo-p-dioxins (CDDs) has been identified as impurity in concentration between 1.5 and 370 ng/g in the Halowax formulations of all type. Halowax 1014 was relatively richer in number of CDD congeners detected when compared to six other CN formulations examined. Amongst the mono- to tri-CDDs, the most prevalent in the Halowaxes were 1- and 2-MoCDD, and especially they were abundant in the formulations of a lower than a higher degree of chlorination. Amongst the tetra- to octaCDD only 1,2,3,4-/1,2,4,6-/1,2,4,9-/ 1,2,3,8-TeCDD, 1,2,3,4,6,7,8-HpCDD and OcCDD were found in all the Halowaxes, and 1,2,3,4,6,7,9-HpCDD remained undetected only in Halowax 1099 and 1013, while most of TeCDDs, PeCDD, and HxCDDs were absent in a majority of the formulations examined. The compositional profile of 1,2,3,4-/1,2,4,6-/1,2,4,9,-/1,2,3,8-TeCDD and OcCDD congeners found in the Halowaxes seem to indicate, that after an initial in situ formation of mono- and di-CDDs during CNs synthesis, a further increase of reaction time, temperature, and pressure can lead to successive chlorination of the already established chlorodibenzo-p-dioxin molecule, and so to enrichment in 1,2,3,4-/ 1,2,4,6-/1,2,4,9,-/1,2,3,8-TeCDD but also OcCDD content for most of the final products obtained. Nevertheless, also due to the co-synthesis of chlorophenols in the Halowaxes, their condensation reactions could also contribute to the formation of CDDs. In term of dioxin-like toxicity the most potent due to CDDs content was Halowax 1014 with 0.95 ng TCDD TEQ/g, and between 0.00068 and 0.058 ng/g were for other formulations. A rough estimation made implies that a net CDDs production due to manufacture of the technical CNs in the XX century could reach an amount between 3.0 and 12.6 kg, while for most toxic dioxin-like constituents between 5.25 and 24 g TCDD TEQ, For the worst case scenario and involvement of Halowax 1014 only the net total CDDs production was estimated to be 1.5 kg, and for highly-toxic congeners 71 g TCDD TEQ. All these figures are much lower when compared to co-production of CDFs.