AbstractThe authors' company has characterised the potential human health and environmental hazards of widely used classes of lubricating oil additives and polyalphaolefin (PAO) base fluids in a battery of toxicity tests. The main classes of additives are: succinimide ashless dispersants, calcium sulphonates, calcium phenates, zinc dialkyldithiophosphates, oxidation inhibitors, and antiwear inhibitors. In summary, mammalian toxicity studies indicate that lubricant additives do not pose a significant health risk to humans. Ecotoxicity is also considered to be of low concern in general. Even though lubricant additives do not readily biodegrade, studies are under way to confirm that they are not persistent in the environment and that bioaccumulation is not a concern. Good Laboratory Practice (GLP) methods have been developed for analysis of additives involved in toxicity tests and for low concentrations (ppb) of additives in aqueous systems. Manufacturing advances are reducing the release of toxic by‐products to the environmen