MUTAGENICITY AND CONTENTS OF POLYCYCLIC AROMATIC-HYDROCARBONS IN NEW HIGH-VISCOSITY NAPHTHENIC OILS AND USED AND RECYCLED MINERAL-OILS

Mutagenic activity on the Ames test was evaluated in 15 samples of nap hthenic high-viscosity mineral oils and 12 samples of used lubricants (recovered and pooled) and their recycled products. Bacterial mutagene sis was assayed using both the standard technique and Blackburn's modi fication. The contents of polycyclic aromatic hydrocarbons (PAH) was a lso evaluated, as polynuclear aromatic fraction (PAF) and total PAH, d etermined respectively with the semi-quantitative dimethylsulphoxide-r efractive index method and the Grimmer method. Only four samples (thre e acid-treated naphthenic oils and one recycled fraction of a used oil ) showed mutagenic activity higher than 6 revertants/mg of oil, consid ered by Blackburn and coworkers as indicating a potential carcinogenic risk for these compounds. Limited mutagenicity was found in all used and recycled oils, but also in samples of acid- or solvent-treated oil s. No hydrogen-treated naphthenic oils turned out to have any mutageni c activity. PAF contents of oils were closely correlated with those of total PAH (n = 15, r = 0.83; n = 12, r = 0.91; p < 0.01 for both naph thenic and used/recycled oils respectively). No recycled oil had high PAF contents. Eleven samples had PAF contents higher than 3%, the arbi trary danger threshold suggested by the CONCAWE (1988). Of these 11 sa mples, the majority were acid-treated products, although there was one hydrogen-treated oil and one used and recycled oil. No mutagenic acti vity could be demonstrated in almost half the oils with PAF > 3%. In t his study, the presence of mutagens was not correlated either with PAF or with total or mutagenic PAH. The difficulty of predicting the muta genicity of mineral oils is stressed. Most naphthenic and some recycle d oils clearly have components which inhibit the metabolizing system i n the bacterial mutagenesis test, with consequent possible false negat ive results.