Toxicological potential of oil-based lubricants marketed in the EU - based on QSAR prediction, and harmonised classification.

Occupational exposure to oil-based lubricants involves inhalation, skin and mucosal surface contact. For hazard characterisation and safe-by-design, identification of toxicity endpoints of lubricant ingredients is desirable. To address this, we a) built a database of 178 oil-based lubricants available in the EU, by extracting CAS Registry numbers of 152 ingredients from safety data sheets (SDSs) (Product-DB), and b) compiled a database of 1032 lubricant ingredients from the Danish Product Registry (Registry-DB). We screened both databases for toxicity using QSAR predictions, EU harmonised classifications, IARC classifications and asthma databases. A dermal toxicity potential was observed for 14 and 17% of the substances in the Product- and Registry-DB, respectively. Reproductive toxicity potential was observed for 11 and 19% of the substances in the Product- and Registry-DB, respectively (7 and 13% when a low-specificity QSAR model is excluded). Although a carcinogenic potential was observed for 7-14% of the substances, none of the SDSs reported the mineral oil base stock as carcinogenic (one SDS flagged titanium dioxide). Other endpoints included hepatotoxicity (13-16% of the substances), and asthma (6% of the substances). Substances that could be considered high priority, based on the number of endpoints and products, identified across both databases, include N‑phenyl‑1‑naphthylamine, 2,6-di-tert-butyl-p-cresol (butylated hydroxytoluene), toluene, methyl methacrylate and maleic anhydride. QSAR prediction in particular pointed to substances with asthma, dermal and reproductive potential not identified by other screening methods, and can help prioritise substances for consideration in hazard characterisation and safe-by-design of oil-based lubricants.