Carcinogenic Assessment of Petroleum Products by Nuclear Magnetic Resonance

Abstract

A method is proposed for improving the assessment of carcinogenicity of petroleum materials by non-animal test means. The proposed method is an extension of the current EU regulatory test method IP 346 which measures a proportion of the polycyclic aromatic compounds present, but does not discriminate between the carcinogenic and the non-carcinogenic species, sometimes resulting in false positive assessments. The proposed method involves the use of high-field proton NMR spectrometry on the IP 346 solvent extract to measure the level of ‘bay region hydrogens’ within polycyclic aromatic molecules. These are structures within the molecule, considered to be directly associated with their carcinogenic potential. Tests on a wide range of petroleum materials using this proton NMR method show that the bay region hydrogen measurement gives greater discrimination between carcinogenic and non-carcinogenic materials than IP 346. The NMR method has not so far given any of the false positives which occur with IP 346 for oils which are not found to be carcinogenic by bioassay. It may also be possible to use the bay region hydrogen measurement as a marker for carcinogenicity in a range of petroleum products which are outside the scope of IP 346.