DDT, A POTENTIAL SOURCE OF ENVIRONMENTAL TRIS(4-CHLOROPHENYL)METHANE AND TRIS(4-CHLOROPHENYL)METHANOL

Tris(4-chlorophenyl)methane (4,4',4''-TCPM) and its presumed metabolite tris(4-chlorophenyl)methanol (4,4',4''-TCPM-OH) are among the most recently identified organochlorine contaminants in environmental biological samples. The compounds are present on a global scale and found in samples from practically all continents. Initially discovered in various aquatic species, they have now also been detected in human milk. However, despite of their widespread occurrence, the source and the origin of these compounds are so far unknown. In this study, we report the first evidence of a link between environmental TCPM and DDT. 4,4',4''-TCPM and two additional isomers, 2,2',4''- and 2,4',4''-TCPM, were formed in small amounts from the reaction of chloral, chlorobenzene, and fumic sulfuric acid under conditions such as those used in the technical synthesis of DDT. The same TCPM isomers were also detected in two samples of technical DDT, one more than 40 years old. In environmental biological samples, particularly at higher trophic levels, generally just a single isomer of TCPM and TCPM-OH is present; the latter was previously identified as the 4,4',4''-isomer, and the same isomerism is now confirmed for the former. Preferred degradation of the isomers with 2-chloro rings in metabolic actions presumably is the reason for the absence of other isomers in biological samples. All 10 possible TCPM isomers were formed in a novel reaction of DDT with chlorobenzene in the presence of AlCl3. They were completely resolved by high-resolution gas chromatography and assigned from retention and mass spectrometric data.