Mutagenic impurities in 1,3-dichloropropene preparations

A widely used pesticide, 1,3-dichloropropene [(DCP) CAS: 542-75-6], has been reported to be mutagenic to Salmonella typhimurium TA100, but large variations in specific mutagenic activity have been observed among different preparations. The purposes of this investigation were to determine the probable cause of the interpreparational variation and to provide new information on the nature of the mutagenic activity. Four preparations were assayed for mutagenic activity before and after silicic acid chromatography. None of the preparations retained mutagenic activity after chromatography, but each contained direct-acting mutagenic polar impurities. The specific mutagenic activities of the unpurified DCP samples appeared to be determined by the mutagenic activities of their polar impurities. A mixture of mutagenic polar impurities could be regenerated by refluxing a purified DCP preparation for 6 hours. The fraction of polar impurities from one of the preparations was analyzed by gas chromatography-mass spectroscopy. Although its composition was too complex to characterize completely, two known mutagens, epichlorhydrin (CAS: 106-89-8; 1-chloro-2,3-epoxypropane) and 1,3-dichloro-2-propanol (CAS: 96-23-1), were tentatively identified. In view of these results, future studies are required to establish whether DCP itself is a chemical carcinogen or whether its previously observed carcinogenicity resulted from the presence of mutagenic impurities.