US EPA

1715091 

Technical Report 

Studies on the formation of chlorodibenzofurans by irradiation or pyrolysis of chlorinated diphenyl ethers 

Norstrom, A; Andersson, K; Rappe, C 

1977 

Yes 

Chemosphere
ISSN: 0045-6535
EISSN: 1879-1298 

CHEM SELECTION WORKING GROUP 

PESTAB/77/1842 

5 

5 

241-248; 1977 

WOS:A1977DS24000006 

PESTAB. The formation of chlorodibenzofurans by pyrolysis or irradiation of chlorinated diphenyl ethers was studied. As previously reported the photolysis of chlorinated diphenyl ethers (PCDEs) follows two competitive reaction pathways, reductive dechlorination or ring closure to dibenzofurans. At least one o-chlorine was needed to give dibenzofurans. When available, o-chlorine was usually cleaved first. The degradation rate was found to be dependent on concentration, i.e., the disappearance of the last part of the substance from the ecosystem will take considerably longer periods of time. The pyrolysis of the four tetrachlorinated isomers resulted in good recovery only of unchanged starting material. However, this does not exclude the possible formation of trace amounts of polychlorinated dibenzofurans (PCDFs), as the detection limit in this case was about 1%. The photochemical ring closure of o-chlorine substituted diphenyl ethers to dibenzofurans seems generally significant and can have environmental implications. The PCDEs are impurities in commercial chlorophenols widely used as herbicides and fungicides and it is therefore recommended that the levels of PCDEs in chloropheols should be kept to a minimum.