Health effects of subchronic exposure to diesel-water-methanol emulsion emission.

The U.S. Environmental Protection Agency's National Ambient Air Quality Standards for ozone and particulate matter (PM) require urban non-attainment areas to implement pollution-reduction strategies for anthropogenic source emissions. The type of fuel shown to decrease combustion emissions components versus traditional diesel fuel, is the diesel emulsion. The Lubrizol Corporation, in conjunction with Lovelace Respiratory Research Institute and several subcontracting laboratories, recently conducted a health assessment of the combustion emissions of PuriNOx diesel fuel emulsion (diesel-water-methanol) in rodents. Combustion emissions from either of two, 2002 model Cummins 5.9L ISB engines, were diluted with charcoal-filtered air to exposure concentrations of 125, 250 and 500 microg total PM/m3. The engines were operated on a continuous, repeating, heavy-duty certification cycle (U.S. Code of Federal Regulations, Title 40, Chapter I) using Rotella-T 15W-40 engine oil. Nitrogen oxide (NO) and PM were reduced when engines were operated on PuriNOx versus California Air Resources Board diesel fuel under these conditions. Male and female F344 rats were housed in Hazleton H2000 exposure chambers and exposed to exhaust atmospheres 6 h/day, five days/week for the first 11 weeks and seven days/week thereafter. Exposures ranged from 61 to 73 days depending on the treatment group. Indicators of general toxicity (body weight, organ weight, clinical pathology and histopathology), neurotoxicity (glial fibrillary acidic protein assay), genotoxicity (Ames assay, micronucleus, sister chromatid exchange), and reproduction and development were measured. Overall, effects observed were mild. Emulsion combustion emissions were not associated with neurotoxicity, reproductive/developmental toxicity, or in vivo genotoxicity. Small decreases in serum cholesterol in the 500-microg/m3 exposure group were observed. PM accumulation within alveolar macrophages was evident in all exposure groups. The latter findings are consistent with normal physiological responses to particle inhalation. Other statistically significant effects were present in some measured parameters of other exposed groups, but were not clearly attributed to emissions exposure. Positive mutagenic responses in several strains of Salmonella typhimurium were observed subsequent to treatment with emulsion emissions subfractions. Based on the cholesterol results, it can be concluded that the 250-microg/m3 exposure level was the no observed effect level. In general, biological findings in exposed rats and bacteria were consistent with exposure to petroleum diesel exhaust in the F344 rat and Ames assays.

Health effects of subchronic exposure to diesel-water emulsion emission.

The U.S. Environmental Protection Agency (EPA) National Ambient Air Quality Standards for ozone and particulate matter are requiring urban nonattainment areas to implement pollution-reduction strategies for anthropogenic source emissions. A type of fuel shown to decrease combustion emissions components versus traditional diesel fuels is the diesel-water emulsion. The Lubrizol Corporation in conjunction with Lovelace Respiratory Research Institute and several subcontracting laboratories recently conducted a rodent health assessment of inhaled combustion emissions of PuriNO(x) diesel fuel emulsion. Combustion emissions from either of two 2001 model Cummins 5.9-L ISB engines were diluted with charcoal-filtered air to exposure concentrations of 100, 200, and 400 microg total particulate matter/m(3). The engines were operated on a continuously repeating, heavy-duty certification cycle (U.S. Code of Federal Regulations, Title 40, Chapter I) using Rotella-T 15W-40 engine oil. Nitrogen oxide and particulate matter were reduced when engines were operated on PuriNO(x) versus California Air Resources Board diesel fuel under these conditions. Male and female F344 rats were housed in Hazleton H2000 exposure chambers and exposed to exhaust atmospheres 6 h/day, 5 days/wk for the first 11 wk and 7 days/wk threafter. Exposures ranged from 58 to 70 days, depending on the treatment group. Indicators of general toxicity (body weight, organ weight, clinical pathology, and histopathology), neurotoxicity (glial fibrillary acidic protein assay), genotoxicity (Ames assay, micronucleus, sister chromatid exchange), and reproduction and development were measured. Overall, effects observed were mild. Emulsion combustion emissions were not associated with neurotoxicity, reproductive/developmental toxicity, or in vivo genotoxicity. Small decreases in serum cholesterol and small increases in platelet values in some groups of exposed animals were observed. Particulate matter accumulation within alveolar macrophages was evident in all exposure groups. These findings are consistent with normal physiological responses to particle inhalation. Other statistically significant effects were present in some measured parameters of other exposed groups but were not clearly attributed to emissions exposure. Positive mutagenic responses in several strains of Salmonella typhimurium were observed subsequent to treatment with emulsion emissions subfractions. Based on the cholesterol and platelet results, it can be concluded that the 100 microg/m(3) exposure level was the no-observed-effect level. In general, biological findings in diesel emulsion emission-exposed animals and bacteria were consistent with exposure to petroleum diesel exhaust in the F344 rat and Ames assays.

Developmental toxicity studies of 2-(difluoromethyl)-dl-ornithine (DFMO) in rats and rabbits.

DFMO, an irreversible inhibitor of ornithine decarboxylase (ODC), is under development as a chemopreventive drug against cancers with pronounced proliferative phases. In support of human clinical trials, preclinical developmental toxicity studies were conducted in pregnant rats and rabbits. Rats were treated during GD 6-17, and fetuses were obtained by C-section on GD 20. Rabbits were treated during GD 7-20, and fetuses were obtained by C-section on GD 29. The dose range-finding study in rats (5/group at 0, 50, 125, 300, 800, or 1000 mg/kg/day) revealed maternal toxicity at doses > or = 800 mg/kg/day (decreased body weights and food consumption) and developmental toxicity at doses > or = 300 mg/kg/day (increased early resorptions and reduced fetal body weights). In the main study, rats (25/group) received 0, 30, 80, or 200 mg/kg/day. Developmental toxicity in the absence of maternal toxicity was observed at 200 mg/kg/day as significantly decreased fetal weights and increased incidence of litters with skeletal variations of 14th rudimentary rib, 14th full rib, and/or 27th presacral vertebrae. There were no treatment-related fetal skeletal malformations or external or visceral anomalies at any dose level. The dose range-finding study in rabbits (5/group at 0, 30, 60, 120, 240, or 500 mg/kg/day) revealed developmental toxicity at doses > or = 60 mg/kg/day (increased resorptions and reduced fetal body weights) in the absence of maternal toxicity. In the main study, rabbits (20/group) received 0, 15, 45, or 135 mg/kg/day. Developmental toxicity in the absence of maternal toxicity was observed at 135 mg/kg/day as nonsignificantly increased early resorptions, decreased implantation sites, decreased viable fetuses, and reduced fetal weights. There were no external, visceral, or skeletal anomalies at any dose level. Thus, in the main developmental toxicity studies, DFMO produced developmental but not maternal toxicity at 200 and 135 mg/kg/day in rats and rabbits, respectively. Accordingly, in rats, the maternal no-observable-effect level (NOEL) was 200 mg/kg/day and the fetal NOEL was 80 mg/kg/day; while in rabbits the maternal NOEL was 135 mg/kg/day and the fetal NOEL was 45 mg/kg/day. These fetal NOELs are several-fold higher than the dose level currently used in Phase II and III clinical trials (approximately 13 mg/kg).

Developmental toxicity of N-methylformamide administered by gavage to CD rats and New Zealand white rabbits.

N-Methylformamide (NMF) is a metabolite of dimethylformamide (DMF), a solvent with wide applications in the chemical industry. The potential developmental toxicity of NMF was evaluated in CD rats and New Zealand white rabbits. Pregnant rats and rabbits were dosed once daily by gavage on Gestation Days 6-15 and 6-18, respectively. Doses for rats were 0, 1, 5, 10, or 75 mg/kg; doses for rabbits were 0, 5, 10, or 50 mg/kg. Cesarean sections were performed on rats and rabbits on Gestation Days 20 and 29, respectively. No treatment-related maternal deaths or clinical signs occurred in either species. Body weight gain and food consumption were depressed in rats given 75 mg/kg and rabbits given 50 mg/kg. Fetal viability was reduced at 75 mg/kg in rats and at 50 mg/kg in rabbits. In rats, a significant increase in the incidence of malformations including cephalocele and sternoschisis was observed in fetuses from the 75 mg/kg group. In addition, a developmental delay was indicated by reduction of fetal weight and by a significant increase in the occurrence of incomplete ossification of various skeletal structures. In the rabbit, fetal body weight was reduced at 50 mg/kg. Malformations observed at 50 mg/kg included gastroschisis, cephalocele, domed head, flexed paw, and skull and sternum anomalies. The lowest-observed-adverse-effect levels for maternal and developmental toxicity in the rat and rabbit were 75 and 50 mg/kg, respectively. The no-observed-adverse-effect level for maternal and developmental toxicity in the rat and rabbit was 10 mg/kg.

Teratogenic assessment of 2,4-dichlorophenol in Fischer 344 rats.

The potential maternal, embryotoxic, and teratogenic parameters of 2,4-dichlorophenol (2,4-DCP) were evaluated in Fischer 344 rats following oral administration in corn oil on Days 6 through 15 of gestation. Dose levels were 0, 200, 375, and 750 mg/kg/day. Females were sacrificed on Gestation Day 20 and cesarean sections performed. The fetuses were weighed, sexed, measured for crown-rump length, and examined for external malformations. A skeletal examination was conducted on one-half of the fetuses after staining with alizarin red S. The remaining fetuses were fixed in Bouin's solution and examined for visceral anomalies and developmental variations. Maternal body weight gain inhibition occurred in all 2,4-dichlorophenol-treated groups during the treatment period. Four treatment-related deaths occurred in the 750 mg/kg/day group. Additional indicators of maternal toxicity included urogenital staining of the fur at all levels tested, and an increased incidence of hair loss and respiratory rales at the 750 mg/kg/day level. Fetal examinations did not reveal differences in the incidence of external, visceral, or skeletal fetal malformations in any treatment group, when compared with the control group. A slight increase in early embryonic death occurred in the high-dose group only. Fetal weights were lower in the high-dose group than in the control group. Variations in skeletal structure were expressed among fetuses exposed to 750 mg/kg/day during organogenesis. These included delayed ossification of sternal elements and vertebral arches. The reduced fetal weights, intrauterine survival, and retarded ossification may represent a slight degree of embryotoxicity or fetotoxicity in this group. The test material was not teratogenic at any dose level.