Increase of the toxic potential of synthetic ester lubricant oils by usage: Application of aquatic bioassays and chemical analysis

The extent by which lubricant oils change their chemical composition and toxicological characteristics by usage is unknown. Risk classification is carried out only with unused fluids. Therefore, a series of lubricant oils based on synthetic esters was examined to characterize the toxic potential before and after an artificial aging process. The samples were examined by standardized bacterial growth assays and a luminescence inhibition test. The results demonstrate an increase of the toxicological potential after usage. A further chemical characterization by atomic absorption spectroscopy (AAS), gas chromatography and mass spectrometry (GC-MS) revealed that volatile compounds like benzene, toluene, ethylbenzene and xylene are produced during the aging process. Heavy metals from catalyts and mechanical devices, are suspected to be partly responsible for the increase in toxicological potential. The alteration of toxicity suggests examination of the new as well as the used lubricant oil fluids for risk classification.