MUTAGENICITY AND CONTENTS OF POLYCYCLIC AROMATIC-HYDROCARBONS IN USEDAND RECYCLED MOTOR OILS

Thirteen samples of used motor oil and 33 recycled fractions, obtained in the laboratory by means of a recovery process similar to that curr ently used in Italy (vacuum distillation followed by thermal clay trea tment) were examined. The Ames test (standard and modified version acc ording to Blackburn) was used to determine the mutagenicity of the ext racts and their contents of polyaromatic fraction (PAF) (IP346/80 meth od) and polycyclic aromatic hydrocarbons (PAH) (Grimmer's method). Use d motor oils are mutagenic, both directly and indirectly. The highest values have been found in used oils from motor vehicles using leaded p etrol (up to 118.8 revertants/mg). Samples from vehicles using unleade d petrol or diesel fuel are less mutagenic (up to 31.1 and 16.4 rev/mg , respectively). The enrichment in mutagens due to the use of oil in t he three types of engine ranges from mean values of 6.2, 1.1 and 0.4 r ev/mg per 1000 km, respectively. Recycled oils are almost completely d evoid of direct mutagenic activity (33 samples: mean +/- SD = 1.6 +/- 1.5 rev/mg). Most recycled distillates show considerable mutagenic act ivity in the presence of microsomial enzymes (up to 82.5 rev/mg), alth ough this is reduced with respect to the original oils (recycled, mean +/- SD = 13.8 +/- 15.5 rev/mg; original oils, mean +/- SD = 30.7 +/- 35.2, Mann-Whitney U-test, z = 1.793, p < 0.05). Both PAF and PAH cont ents are high in used oils from the two types of petrol engine but not in those from diesel engines. Recycling reduces PAF contents only in used oils from petrol engines, from a mean value of 13.91 +/- 7.32 to 4.23 +/- 2,90% (comparison with original used oils, Mann-Whitney U-tes t, U = 8, p < 0.01). The light distilled fractions have greater concen trations of indirect mutagens, PAF and PAH than the others. The increa se in PAH in light recycled products with respect to the original used oils is significant (Wilcoxon's t-test, z = 2.306, p < 0.05). Benzo[a ]pyrene (BaP) is found in appreciable quantities (> 10 ppm) in all use d oils from petrol engines and in most of their recycled products. Rec ycling generally recovers 50% of mutagens and PAF and about 80% of PAH . Considered together, recycled products have in any case contents of mutagens and PAF which are significantly lower than those in the paren t oils, but not of PAH (Wilcoxon's t-test: mutagens, z = 2.935, p < 0. 01; PAF, z = 3.145, p < 0.01; PAH, z = 1.397, not significant). Lastly , many recycled oils have PAH concentrations which are equal to or hig her than those of the original used oils. The health risks linked to p rofessional exposure to these types of oils and the inadequate recycli ng process currently used (redistillation and thermal clay treatment) in reducing mutagenic and cancerogenic substances from used motor oils are stressed.