Identification of 1,3,6-Trinitropyrene as a Major Mutagen in Organic Extracts of Surface Soil from Nagoya City, Japan

Abstract

An organic extract from surface soil collected at a park in Nagoya, Aichi prefecture, which showed extremely high mutagenicity in Salmonella typhimurium TA98 in the absence of a mammalian metabolic system (S9 mix), was investigated to identify the major mutagens. A potent bacterial mutagen was isolated from the organic extract (1.03 g) of the soil sample (2.1 kg) by column chromatography. On the basis of mass spectra, the mutagen, which accounted for 8.8% of the mutagenicity of the soil extract, was thought to be a trinitrated polycyclic aromatic hydrocarbon with a molecular weight of m/z 337. The mutagen was synthesized from pyrene by nitration with nitric acid and was identified as 1,3,6-trinitropyrene (1,3,6-TNP) based on its 1H NMR spectrum. The mutagenicity of 1,3,6-TNP in an Ames assay using S. typhimurium was extremely high, in that it induced 65,500 revertants/nmol in TA98, without S9 mix. This level of activity was slightly lower than that of 1,6-dinitropyrene (DNP), 129,800 revertants/nmol, or 1,8-DNP, 217,000 revertants/nmol, but was greater than that of 1,3-DNP, 4,260 revertants/nmol. These results indicate that 1,3,6-TNP was one of the major mutagens in surface soil collected at a park in Nagoya city, and this is the first report on the detection of 1,3,6-TNP in surface soil.