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No specific quantitative disposition and pharmacokinetic / toxicokinetic studies have been conducted with unrefined / acid treated base oils. Pharmacokinetic / metabolic studies of more highly refined base oils have shown that hydrocarbon components of base oils are absorbed in the gut, can be detected in the blood and lymphatic system, are further transported and may be deposited in the liver, lymph nodes, spleen and other organs and fat-soluble depots. The amount and degree of absorption, distribution, metabolism and excretion of paraffinic, cycloparaffinic and aromatic hydrocarbons depends in general on molecular weight, viscosity and carbon number; carbon numbers greater than C30 will generally not be absorbed well, and carbon numbers less than C18 will be relatively rapidly transformed and / or eliminated.

Disposition of hydrocarbons following inhalation exposure is expected to mimic oral exposure with a similar degree of Absorption, Distribution, Metabolism and Excretion (ADME) are based on the physical parameters of the oil, however the lighter hydrocarbons (<C18) will be present in higher proportions in air than in the oil itself. Absorption of hydrocarbons following dermal exposure is expected to be significantly less than by oral and inhalation routes, with differential penetration capabilities based on molecular weight, carbon number and type. However, the impact to the immediate dermal area can be of significant consequence to health as evidenced by data for polycyclic aromatic constituents (PAC) from chronic dermal administration studies of unrefined and acid treated oils described below.

No metabolism studies have been reported for unrefined / acid treated oils but studies have been reported on the metabolism of C16 and C18 hydrocarbons that are constituents of these oils. In these studies it has been shown that the hydrocarbons are metabolised to the corresponding fatty acids of the same carbon chain length as the parent hydrocarbons, suggesting a process of omega oxidation (Baldwinet al., 1992). Stetten (1943) administered mineral oil containing deuterated hexadecane to rats and monkeys. The deuterium was found to be incorporated into palmitic acid, a fatty acid. McCarthy (1964), using octadecane and hexadecane, confirmed that these hydrocarbons were metabolised to C18 and C16 fatty acids, respectively, in goats, rats and chickens.

No studies have been carried out in man with unrefined / acid treated oils. However, there have been several case reports of the appearance of oil droplets in the spleen, liver and abdominal lymph nodes of people known to or believed to have ingested large quantities of highly refined mineral oil (Boitnott and Margolis, 1970; Stryker, 1941; Cruikshank and Thomas, 1984) or have been exposed to highly refined mineral oils through the food supply. Dincsoy et al. (1982) reported forty cases of lipogranulomas in non-fatty human livers and attributed the finding to ingestion of saturated hydrocarbons, like mineral oil, that are used widely in the food industry. Other reports of the occurrence of tissue accumulation of mineral oils after prolonged exposure, including prolonged usage as laxatives include Wiland and Smith (1957), Rose and Liber (1966), Liber and Rose (1967), Cruickshank (1984) and Blewittet al. (1977). It would be anticipated that unrefined or acid-treated oil components with viscosities similar to the highly refined mineral oils described above would also be retained in certain organs and fat-soluble depots in the human body should exposure and uptake occur.