Evaluation of the dermal carcinogenicity of lubricant base oils by the mouse skin painting bioassay and other proposed methods

Abstract

Lubricant base oils are petroleum products that are predominantly derived from the vacuum distillation of crude oil. Various types of refinement can be employed during the manufacturing process, and evidence suggests that certain of the associated process streams produce skin cancer. Polycyclic aromatic compounds (PACs), some of which are considered as the causative agents, are removed, concentrated or chemically converted during the refinement process. In order to understand the effects of various types of refinement processes on carcinogenic potential, 94 oils were evaluated in the mouse epidermal cancer bioassay. This Exxon database is unique, because of the wide range of crude oils and processing histories represented. Seven processing history classifications are described, and conclusions concerning the impacts of each refinement process on dermal carcinogenicity are discussed. This research also included an evaluation of selected biological and chemical test methods for predicting carcinogenic potential. These included a modified version of the Ames test for mutagenicity, as well as analytical characterizations of the polycyclic aromatic structures in the oils. For classification purposes, a sample was considered to be carcinogenic if it resulted in the production of two or more tumor-bearing animals (in test groups of either 40 or 50 animals). The modified Ames test was considered to be positive if the mutagenicity index was > or = 2.0, and PAC analyses were similarly designated as positive or negative according to proposed guidelines. All of the alternative test methods showed similar agreement with dermal carcinogenicity bioassay data; concordance values were > or = 80%. However, each test was incorrect in ca. 10%-20% of the cases evaluated.(ABSTRACT TRUNCATED AT 250 WORDS)

Petroleum Mineral Oil Refining and Evaluation of Cancer Hazard

“…The mouse is more sensitive to the development of skin tumors than are other laboratory animal species, (17) and skin cancer is the cancer that has been observed in humans exposed to poorly refined oils. (1,18) The method varies slightly between laboratories, (1,5,14,19) but, in general, 50 mice per dose group are given 2-3 weekly applications of 25-50 µl of undiluted oil on a shaved intrascapular area of the back. Mice are either caged together (approximately 6/cage) or individually housed in wire mesh cages.…”

“…These tests involve the biological or chemical characterization of the PAC in base oils. (4)(5)(6)(7) Three of these assays have been validated for use in screening vacuum distillate and residual oil streams for carcinogenic potential and potency.…”

“…By the 1980s, individual companies were using their own short-term analytical 891 or biological assays for assessing carcinogenic potential of base oils. (4)(5)(6) Three short-term screening assays 1) the modified Ames test, (2,7,8) 2) the measurement of 3-7-ring PAC (Mobil method), (3,7,8) and 3) percent wt. of oil extracted into DMSO (IP 346), (9,10) are sufficiently validated for general use by all base oil refiners and are described in this review.…”

Lubricant Base Oils: Analysis and Characterization of

“…49 The time of tumor development and the percentage of animals developing tumors relative to the controls are used to assess carcinogenicity. A bioassay test and DMSO extraction tests have been developed to predict the results of mouse-painting tests to reduce the time and cost to assess carcinogenicity.…”

Assessing cancer hazards of bitumen emissions – a case study for complex petroleum substances

“…The paving fume condensate was straight run and the type-III BURA was oxidized. The mouse skin-painting study is a sensitive indicator of dermal carcinogenic potential, particularly for complex petroleum substances, where carcinogenicity may be mediated by PACs (Chasey and McKee 1993;Kriech et al 1999a).…”