Toxicology and carcinogenesis studies were conducted by applying marine diesel fuel or JP-5 navy fuel to clipped dorsal interscapular skin of male and female B6C3F1 mice to determine both systemic and dermal effects. Doses for the 2-year studies were set by conducting 14-day and 13-week studies. Doses of 2,000-40,000 mg/kg marine diesel fuel were applied neat in the 14-day studies; in the 13-week studies, doses of 250-4,000 mg/kg marine diesel fuel in acetone were applied with a dose volume of 0.1 ml. Doses of 5,000-40,000 mg/kg JP-5 navy fuel in ethanol were applied in the 14-day studies with a dose volume of 0.5 ml; in the 13-week studies, doses of 500-8,000 mg/kg JP-5 navy fuel in acetone were applied with a dose volume of 0.2 ml. For the 2-year studies, doses were selected which did not cause deaths, decrease body weight gain, or produce excessive dermatitis in the 14-day or 13-week studies. Two-year studies were conducted by administering marine diesel fuel or JP-5 navy fuel by dermal application to groups of 49 or 50 male and 50 female B6C3F1 mice at doses of 0, 250, or 500 mg/kg in an acetone vehicle with a dose volume of 0.1 ml.
Both sexes of mice dosed with 500 mg/kg marine diesel fuel (84-week exposure) and female mice dosed with 500 mg/kg JP-5 navy fuel (90-week exposure) were killed early because of excessive irritation and ulceration at the site of application and to prevent the spread of infection. Survival rates at those times were 26/50 males and 29/50 females dosed with marine diesel fuel and 17/50 females dosed with JP-5 navy fuel. Survival rates at the end of the studies (104 weeks) were reduced (P<0.01) in low dose female mice receiving marine diesel fuel (40/50 in vehicle controls compared with 12/50 in the low dose group) or with JP-5 navy fuel (44/50 in vehicle controls compared with 33/50 in the low dose group). Body weight gain was decreased below that of the vehicle controls after week 30 in all groups of mice receiving marine diesel fuel and in both sexes of mice receiving the high dose of JP-5 navy fuel.
There was a marked increase in the incidence of chronic dermatitis in mice receiving marine diesel fuel or JP-5 navy fuel. Chronic dermatitis was defined as a composite lesion of epidermal histopathologic changes generally consisting of acanthosis, hyperkeratosis, and in some instances necrosis and ulceration of the overlying epidermis. Dermal changes frequently included fibrosis, increased amounts of melanin, and the presence of acute and chronic inflammatory cell infiltrates. A dose-related, proportional increase in the severity of the lesions was twofold to threefold greater in the dosed groups than in the vehicle controls. The averagedegree of severity of the lesions was judged to be minimal in the vehicle controls, mild in the low dose groups, and moderate in the high dose groups of mice dosed with marine diesel fuel or JP-5 navy fuel. There were similar responses at the site of inguinal skin to which the chemicals had migrated after application, but the degree of severity of the lesions was judged to be minimal to mild in the vehicle control and dosed groups of mice.
Squamous cell papillomas or carcinomas (combined) occurred with a positive trend (P<0.05) at the site of application in male mice administered marine diesel fuel (vehicle control, 0/49; low dose, 0/49; high dose, 3/49). The total numbers of mice with squamous cell papillomas or carcinomas (combined) both for the site of application and the adjacent inguinal skin were 1/50, 2/49, and 3/50 for the vehicle control, low dose, and high dose groups of male mice and 0/50, 1/45, and 2/48 for female mice. There are no NTP historical data for B6C3F1 mice that received acetone by dermal application. The NTP historical incidence of squamous cell papillomas or carcinomas (combined) in untreated male and female B6C3F1 mice is 0.3%-0.4% in over 3,500 observations.
Marine diesel fuel was not mutagenic in Salmonella typhimurium TA98, TA100, TA1535, or TA1537, and JP-5 navy fuel was not mutagenic in strains TA97, TA98, TA100, or TA1535 in the presence or absence of Aroclor 1254-induced male Sprague-Dawley rat or male Syrian hamster S9 when tested according to the preincubation protocol.
Audits of the experimental data were conducted for these 2-year studies on marine diesel fuel and JP-5 navy fuel. No data discrepancies were found that influenced the final interpretations.
Under the conditions of these 2-year dermal studies, marine diesel fuel at doses of 250 and 500 mg/kg resulted in dose-related increased incidences of squamous cell neoplasms of the skin (primarily carcinomas), providing equivocal evidence of carcinogenicity for male and female B6C3F1 mice. The sensitivity for detecting systemic carcinogenicity in female mice dosed with marine diesel fuel was reduced by poor survival. Under the conditions of these 2-year dermal studies, JP-5 navy fuel at doses of 250 and 500 mg/kg provided no evidence of carcinogenicity for male and female B6C3F1 mice.