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Roberts L.G.,Chevron | Gray T.M.,American Petroleum Institute | Trimmer G.W.,ExxonMobil | Parker R.M.,Princeton Research Center | And 3 more authors.
Regulatory Toxicology and Pharmacology | Year: 2014

Gasoline-vapor condensate (BGVC) or condensed vapors from gasoline blended with methyl t-butyl ether (G/MTBE), ethyl t-butyl ether (G/ETBE), t-amyl methyl ether (G/TAME) diisopropyl ether (G/DIPE), ethanol (G/EtOH), or t-butyl alcohol (G/TBA) were evaluated for developmental toxicity in Sprague-Dawley rats exposed via inhalation on gestation days (GD) 5-20 for 6h/day at levels of 0 (control filtered air), 2000, 10,000, and 20,000mg/m3. These exposure durations and levels substantially exceed typical consumer exposure during refueling (<1-7mg/m3, 5min). Dose responsive maternal effects were reduced maternal body weight and/or weight change, and/or reduced food consumption. No significant malformations were seen in any study. Developmental effects occurred at 20,000mg/m3 of G/TAME (reduced fetal body weight, increased incidence of stunted fetuses), G/TBA (reduced fetal body weight, increased skeletal variants) and G/DIPE (reduced fetal weight) resulting in developmental NOAEL of 10,000mg/m3 for these materials. Developmental NOAELs for other materials were 20,000mg/m3 as no developmental toxicity was induced in those studies. Developmental NOAELs were equal to or greater than the concurrent maternal NOAELs which ranged from 2000 to 20,000mg/m3. There were no clear cut differences in developmental toxicity between vapors of gasoline and gasoline blended with the ether or alcohol oxygenates. © 2014 Elsevier Inc. Source


Roberts L.G.,Chevron | Gray T.M.,American Petroleum Institute | Marr M.C.,Rti International | Tyl R.W.,Rti International | And 3 more authors.
Regulatory Toxicology and Pharmacology | Year: 2014

CD-1 mice were exposed to baseline gasoline vapor condensate (BGVC) alone or to vapors of gasoline blended with methyl tertiary butyl ether (G/MTBE). Inhalation exposures were 6h/d on GD 5-17 at levels of 0, 2000, 10,000, and 20,000mg/m3. Dams were evaluated for evidence of maternal toxicity, and fetuses were weighed, sexed, and evaluated for external, visceral, and skeletal anomalies. Exposure to 20,000mg/m3 of BGVC produced slight reductions in maternal body weight/gain and decreased fetal body weight. G/MTBE exposure did not produce statistically significant maternal or developmental effects; however, two uncommon ventral wall closure defects occurred: gastroschisis (1 fetus at 10,000mg/m3) and ectopia cordis (1 fetus at 2000mg/m3; 2 fetuses/1 litter at 10,000mg/m3). A second study (G/MTBE-2) evaluated similar exposure levels on GD 5-16 and an additional group exposed to 30,000mg/m3 from GD 5-10. An increased incidence of cleft palate was observed at 30,000mg/m3 G/MTBE. No ectopia cordis occurred in the replicate study, but a single observation of gastroschisis was observed at 30,000mg/m3. The no observed adverse effect levels for maternal/developmental toxicity in the BGVC study were 10,000/2000mg/m3, 20,000/20,000 for the G/MTBE study, and 10,000/20,000 for the G/MTBE-2 study. © 2014 The Authors. Source


Murray F.J.,Murray and Associates | Sullivan F.M.,Harrington House | Tiwary A.K.,Chevron | Carey S.,International Molybdenum Association
Regulatory Toxicology and Pharmacology | Year: 2014

This study investigated the subchronic toxicity of molybdenum (Mo) in Sprague-Dawley rats given sodium molybdate dihydrate in the diet for 90days at dose levels of 0, 5, 17 or 60mgMo/kgbw/day. The study complied with OECD Test Guideline (TG) 408, with additional examination of estrus cycles and sperm count, motility, and morphology from OECD TG 416. The overall no-observed-adverse-effect level was 17mgMo/kgbw/day, based on effects on body weight, body weight gain, food conversion efficiency and renal histopathology (females only) at 60mgMo/kgbw/day. No treatment-related adverse effects on reproductive organ weights or histopathology, estrus cycles or sperm parameters were observed at any dose level. No adverse effects were observed in the high dose animals after the 60-day recovery period, with the exception that male rats did not fully recover from reduced body weight. Serum blood, liver and kidney samples were analyzed for molybdenum, copper, zinc, manganese, iron, cobalt and selenium; high levels of molybdenum and copper were found in the serum, blood, liver and kidneys of rats treated with 60mgMo/kgbw/day. In conclusion, the LOAEL and NOAEL for molybdenum were determined to be 60 and 17mgMo/kgbw/day, respectively. © 2013 The Authors. Source


Murray F.J.,Murray and Associates
Food and Chemical Toxicology | Year: 2011

4-Methylimidazole (4-MEI) is found in a wide array of food products. The National Toxicology Program (NTP) recently conducted a two-year feeding cancer bioassay of 4-MEI in B6C3F1 mice and F344/N rats. In rats, NTP found "equivocal evidence of carcinogenic activity" in females based on increased incidences of mononuclear cell leukemia and "no evidence of carcinogenic activity" in males. However, dose-related, statistically significant decreases in multiple tumors were observed in both male and female rats exposed to 4-MEI in the NTP bioassay. For example, 4-MEI was associated with a 25-fold decrease in the incidence of mammary tumors among high dose females. NTP noted briefly that the decreases in certain tumors, including mammary tumors, were greater than could be attributed to body weight alone. The present paper provides a more detailed evaluation of the evidence that 4-MEI exhibits tumor preventive activity in the rat based upon the results of the NTP bioassay. Reduced body weight offers a partial explanation for the reduction in tumors, but does not appear to be the primary cause of the decreased tumor incidences, indicating that 4-MEI itself may possess an ability to prevent tumor formation. © 2010 Elsevier Ltd. Source


Cruzan G.,ToxWorks | Harkema J.R.,Michigan State University | Hosako H.,WIL Research Laboratories LLC | Wasil J.M.,WIL Research Laboratories LLC | Murray F.J.,Murray and Associates
Regulatory Toxicology and Pharmacology | Year: 2015

4-Methylimidazole (4-MEI) occurs in certain foods and beverages as a product of browning reactions. An increased incidence of lung tumors was reported in mice, but not rats, exposed to levels of 4-MEI in their diet that far exceed human dietary intake. This investigation evaluated the hypothesis that 4-MEI induces mouse lung tumors by the same mode of action (MOA) as styrene: CYP2F2 metabolic activation and increased BrdU labeling. Using styrene (200 mg/kg/day by gavage) as a positive control, histopathology and DNA synthesis (measured by BrdU incorporation) in the bronchiolar region were evaluated in: (1) a 5-day comparative toxicity study in C57BL/6 "wild type" and CYP2F2 "knock out" (KO) mice given 4-MEI at the same dietary concentrations used in the NTP cancer bioassay, and (2) a 13-week comparative toxicity study of C57BL/6 and B6C3F1 mice receiving 0, 1250 or 2500 ppm of 4-MEI in the diet for 6, 15, 34 and 91 days. In contrast to styrene, 4-MEI had no consistent effect on BrdU labeling or histopathology in the lungs of mice in the dose range that had been shown to produce lung tumors in another study. The results of these studies do not support the hypothesis that 4-MEI and styrene induce lung tumors by the same MOA. © 2015 Published by Elsevier Inc. Source

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