Carcinogenic potential of hydrotreated petroleum aromatic extracts.

Abstract

Five experimental petroleum extracts were produced from luboil distillates derived from Middle East paraffinic crude by solvent extraction and severe hydrotreatment. The polycyclic aromatic content (PCA) of the extracts was determined by dimethyl sulphoxide extraction and ranged from 3.7-9.2% w/w. The five extracts were evaluated for their potential to induce cutaneous and systemic neoplasia in female mice derived from Carworth Farm No 1 strain (CF1). The test substances were applied undiluted (0.2 ml per application) to the shorn dorsal skin twice weekly for up to 78 weeks, with 48 mice in each treatment group and 96 in the untreated control group; two further groups, each of 48 mice, were similarly treated either with a non-hydrotreated commercial aromatic extract (PCA content, 19.7% w/v) or with a low dose of benzo(a)pyrene (12.5 micrograms/ml acetone). The mice were housed individually in polypropylene cages in specified pathogen free conditions. The incidence of cutaneous and systemic tumours was determined from histological analysis of haematoxylin and eosin stained tissue sections. The results were correlated with the PCA content of the extracts and compared with those from female mice exposed to a non-hydrotreated commercial aromatic extract. Four of the hydrotreated extracts were carcinogenic for murine skin; the two products with the lower PCA contents were less carcinogenic than the products with the higher PCA contents and all were less carcinogenic than the commercial extract. One extract with the lowest PCA content was non-carcinogenic. Thus refining by severe hydrotreatment was an effective method of reducing the carcinogenic potential of petroleum aromatic extracts. Although other physicochemical properties may influence the biological activity of oil products, the PCA content determined by dimethyl sulphoxide extraction may be a useful indicator of the potential of oil products to induce cutaneous tumours in experimental animals. There was no evidence that the commercial or hydrotreated extracts increased the incidence of systemic neoplasms when applied twice weekly to the dorsal skin.

Mineral oil in food, cosmetic products, and in products regulated by other legislations

“…HRBO and OLBO are commonly known as "mineral oils". Test materials were applied undiluted in a defined volume to the shaved backs of the animals 1-3 times per week (Doak et al 1983;Blackburn et al 1984;Doak et al 1985;Blackburn et al 1986;Roy et al 1988;McKee, Daughtrey, et al 1989;McKee, Nicolich, et al 1990;Chasey and McKee 1993;Concawe 1994). In some cases, test materials were diluted in highly refined mineral oil or toluene for reasons of high toxicity or high viscosity (Blackburn et al 1986;McKee, Daughtrey, et al 1989;McKee, Nicolich, et al 1990).…”

“…Only some studies reported the size of the dermal treatment area (McKee, Daughtrey, et al 1989;Chasey and McKee 1993). White mineral oil and toluene were reported to be used as negative/ vehicle controls, and B[a]P (in toluene or acetone) and catalytically cracked clarified oil as positive controls (Doak et al 1985;Blackburn et al 1986;McKee, Daughtrey, et al 1989;McKee, Nicolich, et al 1990;). Shaved but untreated animals were reported to be used as additional negative controls (Doak et al 1985;Blackburn et al 1986;.…”

Predicting carcinogenicity of petroleum distillation fractions using a modified Salmonella mutagenicity assay

“…At the same time, epidemiological studies (Cruickshank and Squire, 1950;Cruickshank and Gourevitch, 1952;Waterhouse, 1971; and Thony and Thony, 1970) have linked exposure to unrefined oils to an excess incidence of skin cancer in humans. Chemical analysis of the carcinogenic oils showed that a portion of the carcinogenic activity can be attributed to the presence of polycyclic aromatic hydrocarbons (PAHs) (Bingham et al, 1965(Bingham et al, , 1969Grimmer et al, 1982;Gradisky et al, 1983;and Doak et al, 1985). This association has been supported by the observation that solvent refining, which quantitatively removes PAHs from oils, eliminates carcinogenic activity (Bingham and Horton, 1966;Doak et al, 1983;Halder et al, 1984;and Kane et al, 1984).…”

Subchronic and Developmental Toxicity of Aromatic Extracts

“…Therefore, DAEs are generally expected to contain relatively high amounts of PACs and to be carcinogenic. [12][13][14][15] Vacuum residues are much less carcinogenic than distillates, 16 and RAEs are less carcinogenic than DAEs. [12][13][14] The primary route of concern is dermal due to the high viscosity of AEs (limiting aerosolization) and the anticipated uses of these products in end uses in which dermal exposure is the most likely route of exposure.…”