David R. Mattie

A 90-Day Continuous Vapor Inhalation Toxicity Study of JP-8 Jet Fuel Followed by 20 or 21 Months of Recovery in Fischer 344 Rats and C57BL/6 Mice

The kerosene-type jet fuel, JP-8, consists of a complex mixture of aliphatic and aromatic hydrocarbons. Because of the utility of JP-8, studies have been conducted to identify the potential long-term consequence of occupational inhalation exposure. Fischer 344 rats and C57BL/6 mice of both sexes were exposed to JP-8 vapors at 0, 500, and 1,000 mg/m3 on a continuous basis for 90 days, then followed by recovery until approximately 24 months of age. Occurrence of necrotizing dermatitis associated with fighting resulted in an increase in mortality in mice (male greater than female) during the 2 week to 9 month post-exposure recovery period. The male rat kidney developed a reversible ultrastructural increase in size and propensity for crystalloid changes of phagolysosomal proteinic reabsorption droplets in the proximal convoluted tubular epithelium. A specific triad of persisting light microscopic renal lesions occurred but functional change was limited to a decrease in urine concentration compared to controls that persisted throughout the recovery period. The response is comparable to the chronic effect of lifetime exposure of the male rat to unleaded gasoline, d-limonene, and p-dichlorobenzene, except for the absence of tubular tumorigenesis. The active toxicologic response presumably must occur over a greater proportion of the male rats life span for the tumor component of this male rat hydrocarbon nephropathy syndrome. The predictiveness for humans must be questioned, since the pathologic response to JP-8 involved only one tissue in one sex of one species, and since the male rat response appears to be linked to an inherent renal protein peculiarity.

Developmental toxicity of JP-8 jet fuel in the rat

JP‐8 aviation fuel is being phased in as a replacement for both JP‐4 and JP‐5 jet fuels presently in use by the Air Force and Navy, respectively. At the present time, 11% of active‐duty Air Force personnel are women of child‐bearing age. This study was undertaken to determine the threat posed to the unborn fetus should female active‐duty personnel come in contact with JP‐8 while pregnant. Time‐mated Sprague‐Dawley rats were dosed orally with JP‐8 at 0, 500, 1000, 1500 and 2000u2009mgu2009kg−1 day−1 on days 6–15 of pregnancy. The number and type of fetal malformations and variations observed did not differ significantly between dose groups. Dams in the 1000, 1500 and 2000 mgu2009kg−1 day−1 groups gained significantly less body weight during pregnancy than did control dams. Embryo toxicity was indicated by a significant reduction in fetal body weight in the 1500 and 2000u2009mgu2009kg−1 day−1 dose groups.

Pathological and hepatic ultrastructural effects of a single dose of perfluoro-n-decanoic acid in the rat, hamster, mouse, and guinea pig

In rats, the liver is the primary target organ of perfluoro-n-decanoic acid (PFDA) toxicity. Therefore, the effects of PFDA on hepatic ultrastructure were studied in rats. Pathological changes induced by PFDA in hamsters, mice, and guinea pigs were also examined. PFDA caused a severe reduction in body weight in all four species studied. A reduction in food intake was observed in rats and hamsters. However, hamsters continued to consume food at a reduced level, while rats stopped eating for a 5- to 6-day period about 6 days after dosing. The PFDA-induced pathological changes in the hamsters, mice, and guinea pigs resembled those seen in rats to varying degrees. As in the rat, PFDA caused a marked liver enlargement in mice and hamsters and a moderate swelling in guinea pigs. This hepatomegaly was ascribed primarily to individual cell swelling. Thymic atrophy was noted in PFDA-treated hamsters, mice, and guinea pigs. Seminiferous tubular degeneration observed in hamsters and guinea pigs, but not in mice, was not as severe as in the rat, where in some cases frank necrosis has been seen. Ultrastructural changes in the livers of all PFDA-treated animals, regardless of species, included disruption of the rough endoplasmic reticulum, rounding and swelling of the mitochondria with related structural alterations, and mild to extensive proliferation of peroxisomes. This peroxisome proliferative response was greatest in mice and almost absent in guinea pigs. Accumulation of lipid droplets in liver cells due to PFDA treatment was more pronounced in hamsters and guinea pigs than in rats and mice. PFDA-induced hepatomegaly with a concomitant increase in peroxisomes in several rodent species may be associated with an impairment of normal lipid metabolism in the liver by PFDA.

The Effects of Jp-8 Jet Fuel on Male Sprague-Dawley Rats after a 90-Day Exposure By Oral Gavage

The U.S. Air Force is converting from JP-4 jet fuel to the less volatile JP-8 jet fuel, which is similar to commercial Jet Fuel A. Our previous 90-day inhalation study with JP-8 vapor, using F-344 rats and C57BL/6 mice, resulted in no treatment-related adverse effects other than α 2-microglobin nephropathy in male rats (Mattie et al., 1991). In the present study, male rats were dosed with neat JP-8 (0, 750, 1500, 3000 mg/kg) daily by gavage for 90 days in an effort to characterize the kidney lesion and assess further any additional adverse effects associated with prolonged oral exposure to this fuel. Results of this study revealed a significant dose-dependent decrease in body weights of rats exposed to JP-8. Male rat-specific α 2-microglobin nephropathy was observed by histopathologic examination. A number of significant changes were also seen in blood and urine that were not dose-dependent. Additional treatment-related effects were a gastritis and a perianal dermatitis. Although there were no histopathological or weight changes in the livers of exposed rats, there was an increase in the liver enzymes AST and ALT. The elevated enzymes did not increase with increasing dose of JP-8.

Evaluation of Perturbations in Serum Thyroid Hormones During Human Pregnancy Due to Dietary Iodide and Perchlorate Exposure Using a Biologically Based Dose-Response Model

A biologically based dose-response model (BBDR) for the hypothalamic pituitary thyroid (HPT) axis was developed in the near-term pregnant mother and fetus. This model was calibrated to predict serum levels of iodide, total thyroxine (T4), free thyroxine (fT4), and total triiodothyronine (T3) in the mother and fetus for a range of dietary iodide intake. The model was extended to describe perchlorate, an environmental and food contaminant, that competes with the sodium iodide symporter protein for thyroidal uptake of iodide. Using this mode-of-action framework, simulations were performed to determine the daily ingestion rates of perchlorate that would be associated with hypothyroxinemia or onset of hypothyroidism for varying iodide intake. Model simulations suggested that a maternal iodide intake of 75 to 250 µg/day and an environmentally relevant exposure of perchlorate (~0.1 µg/kg/day) did not result in hypothyroxinemia or hypothyroidism. For a daily iodide-sufficient intake of 200 µg/day, the dose of perchlorate required to reduce maternal fT4 levels to a hypothyroxinemic state was estimated at 32.2 µg/kg/day. As iodide intake was lowered to 75 µg/day, the model simulated daily perchlorate dose required to cause hypothyroxinemia was reduced by eightfold. Similarly, the perchlorate intake rates associated with the onset of subclinical hypothyroidism ranged from 54.8 to 21.5 µg/kg/day for daily iodide intake of 250-75 µg/day. This BBDR-HPT axis model for pregnancy provides an example of a novel public health assessment tool that may be expanded to address other endocrine-active chemicals found in food and the environment.

A Rat Neurodevelopmental Evaluation of Offspring, Including Evaluation of Adult and Neonatal Thyroid, from Mothers Treated with Ammonium Perchlorate in Drinking Water

The purpose of this study was to evaluate the potential neurodevelopmental toxicity of perchlorate exposure during gestation and the first 10 days of lactation. Mated Sprague-Dawley rats (25/exposure group) were given continual access to 0, 0.1, 1.0, 3.0, or 10.0 mg/kg-day ammonium perchlorate (AP) in drinking water, starting gestation day 0 (mating) through lactation day 10 (DL 10). One pup/sex/litter/exposure group was assigned to (1) juvenile brain weights, morphometry, and neuropathology; (2) passive avoidance and watermaze testing; (3) motor activity and auditory startle habituation; and (4) adult regional brain weights, morphometry, and neuropathology. AP had no effect on body weights, feed consumption, clinical observations, or sexual maturation of pups at exposures as high as 10.0 mg/kg-day. There were no behavioral effects in the offspring exposed as high as 10.0 mg/kg-day as evaluated by passive avoidance, swimming watermaze, motor activity, and auditory startle. Increases in hypertrophy and hyperplasia of the thyroid follicular epithelium and a decrease in the thyroid follicle size were observed in culled male pups in the 10.0 mg/kg-day group on DL 5. The exposure level for effects on triiodothyroxine (T3), thyroxine (T4), and thyroid-stimulating hormone (TSH) levels for pups were 0.1, 1.0, and 3.0 mg/kg-day, respectively. There was an apparent increase in the thickness of the corpus callosum of the 10 mg/kg-day group pups on DL 12. The no-observed-adverse-effect level (NOAEL) for maternal toxicity was greater than 10.0 mg/kg-day. Based on the thyroid morphometric and histopathologic findings, the NOAEL for pup toxicity was 0.1 mg/kg-day.

Past, present and emerging toxicity issues for jet fuel

The US Air Force wrote the specification for the first official hydrocarbon-based jet fuel, JP-4, in 1951. This paper will briefly review the toxicity of the current fuel, JP-8, as compared to JP-4. JP-8 has been found to have low acute toxicity with the adverse effects being slight dermal irritation and weak dermal sensitization in animals. JP-4 also has low acute toxicity with slight dermal irritation as the adverse effect. Respiratory tract sensory irritation was greater in JP-8 than in JP-4. Recent data suggest exposure to jet fuel may contribute to hearing loss. Subchronic studies for 90 days with JP-8 and JP-4 showed little toxicity with the primary effect being male rat specific hydrocarbon nephropathy. A 1-year study was conducted for JP-4. The only tumors seen were associated with the male rat specific hydrocarbon nephropathy. A number of immunosuppressive effects have been seen after exposure to JP-8. Limited neurobehavioral effects have been associated with JP-8. JP-8 is not a developmental toxicant and has little reproductive toxicity. JP-4 has not been tested for immune, neurobehavioral or reproductive endpoints. JP-8 and JP-4 were negative in mutagenicity tests but JP-4 showed an increase in unscheduled DNA synthesis. Currently, JP-8 is being used as the standard for comparison of future fuels, including alternative fuels. Emerging issues of concern with jet fuels include naphthalene content, immunotoxicity and inhalation exposure characterization and modeling of complex mixtures such as jet fuels.

Oral (Drinking Water) Developmental Toxicity Study of Ammonium Perchlorate in Sprague-Dawley Rats

A developmental toxicity study was conducted with ammonium perchlorate (AP) in the drinking water at doses of 0.0, 0.01, 0.1, 1.0, and 30.0 mg/kg-day beginning 14 days before cohabitation and continuing through sacrifice. Twenty-four rats/group were cesarean-sectioned on day of gestation (DG) 21 and fetuses examined for visceral and skeletal alterations. An additional 16 litters/group were sacrificed on DG 21 for maternal and fetal serum TSH, T3, and T4 (thyroid-stimulating hormone, triiodothyronine, and thyroxine) levels and thyroid histopathology. Clinical and necropsy observations, body weights, feed and water consumption, and cesarean-sectioning parameters were comparable among the groups with only delays in ossification observed in the 30 mg/kg-day group. Maternal thyroid weights were increased in the 30.0 mg/kg-day group. Decreased colloid was present in male and female fetal thyroids in the 1.0 and 30.0 mg/kg-day groups. Maternal TSH was increased and T4 was decreased at all levels, and T3 was reduced at 30.0 mg/kg-day. Fetal TSH was increased at 1.0 and 30.0 mg/kg-day, T4 was reduced at 30.0 mg/kg-day, and T3 was decreased at all levels. The maternal no-observable-adverse-effect level (NOAEL) was 1.0 mg/kg-day; exposures of 30.0 mg/kg-day increased absolute and relative maternal thyroid weights and histopathology findings. The developmental NOAEL was 1.0 mg/kg-day; developmental delays in ossification occurred in the 30.0 mg/kg-day group. The colloid depletion in the thyroids and increased TSH and decreased T3 and T4 levels at lower exposures were considered adaptive and not adverse. No adverse effects on development at occurred levels that did not cause maternal toxicity. AP is not a selective developmental toxicant.

Age-Dependent Partition Coefficients for a Mixture of Volatile Organic Solvents in Sprague-Dawley Rats and Humans

The absorption, distribution, metabolism, and excretion of volatile organic compounds (VOCs) are critically determined by a few chemical-specific factors, notably their blood and tissue partition coefficients (PC) and metabolism. Age-specific values for PCs in rats have rarely been reported or utilized in pharmacokinetic modeling for predicting dosimetry in toxicity studies with rats progressing through their lifestages. A mixture of six VOCs (benzene, chloroform, methyl ethyl ketone, methylene chloride, trichloroethylene, and perchloroethylene) was used to determine blood:air and tissue:air PCs in rats at three different ages (postnatal d 10, 60 d, and 2 yr) and blood:air PCs in pediatric and adult human blood. No differences with age in human blood:air PCs for the six compounds were observed. Rat blood:air PCs increased with age varying with compound. Tissue:air PCs showed tissue-specific changes with age. Water-soluble methyl ethyl ketone showed no age-dependent differences. Partition coefficients, particularly the blood:air PC, are key determinants of the rodent and human blood concentrations; age-appropriate values improve the accuracy of pharmacokinetic model predictions of population variability and age-specific exposures.

Alterations in alveolar clearance after 4-ipomeanol-induced necrosis of Clara and ciliated cells in the terminal bronchiole of the rat

The administration of 4-ipomeanol, [0, 10 (LD), and 25 (HD) mg/kg, ip], to rats resulted in dose-dependent degeneration and necrosis of the nonciliated (Clara) and ciliated epithelial cells of the terminal bronchioles. More extensive necrosis of the terminal bronchiolar epithelium, with exposure of the basement membrane, was produced in the HD group. Repair of the terminal bronchiolar epithelium was complete within 10 days. Alveolar clearance of 51Cr labeled polystyrene latex microspheres was analyzed through 40 days postinstillation by nonlinear regression for a double exponential model. Alveolar clearance during phase 1 (Days 2 to 6) was delayed and significantly decreased in both the LD and HD groups. Alveolar clearance during phase 2 (Days 10 to 40) was significantly decreased only in the HD group. The decreased alveolar clearance in HD subjects was long term and did not correlate with the return of morphologically normal appearing Clara and ciliated cell structure.