Formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans and their precursors in fires of pyrethroid pesticide alpha-cypermethrin

This study reports the results of the gas phase oxidation of alpha-cypermethrin, a common insecticide, elucidating the decomposition pathways and formation of toxic species such as polychlorinated dibenzo-pdioxins and polychlorinated dibenzofurans (PCDD/F) and their precursors. Conditions investigated are similar to those encountered in post combustion and cooling-down zones of forest, agricultural and wild fires, as well as in burning of biomass contaminated or treated with pesticides. The experiments were conducted under fuel lean conditions in a tubular reactor housed in a three-zone heating furnace and operated with a dilute stream of alpha-cypermethrin in ultra high purity nitrogen and oxygen. PCDD/F were identified and quantified by high resolution gas chromatography (HRGC)-ion trap mass spectrometry (ITMS). We detected mono to hepta chlorinated dibenzo-p-dioxins and dibenzofurans with maximum emission factors of 141 μg g^-1 and 384 pg ΣTEQ-WHO₂₀₀₅ g^-1 of alpha-cypermethrin. 1-monochlorodibenzofuran was ranked as the most abundant congener. We also conducted the analyses of volatile organic compounds (VOC) attempting to identify the PCDD/F precursors by means of HRGCquadrupole mass spectrometry (QMS). The results of VOC revealed chlorobenzene, diphenyl ether, benzaldehyde, chlorotoluene, dichlorotoluene as important PCDD/F precursors.