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The primary alternative to petroleum-based fuels is ethanol, which may be blended with gasoline in the United States at concentrations up to 15% for most automobiles. Efforts to increase the amount of ethanol in gasoline have prompted concerns about the potential toxicity of inhaled ethanol vapors from these fuels. The well-known sensitivity of the developing nervous and immune systems to ingested ethanol and the lack of information about the neurodevelopmental toxicity of ethanol-blended fuels prompted the present work. Pregnant Long-Evans rats were exposed for 6.5 h/day on days 9-20 of gestation to clean air or vapors of gasoline containing no ethanol (ED) or gasoline blended with 15% ethanol (E15) or 85% ethanol (E85) at nominal concentrations of 3000, 6000, or 9000 ppm. Estimated maternal peak blood ethanol concentrations were less than 5 mg/dL for all exposures. No overt toxicity in the dams was observed, although pregnant dams exposed to 9000 ppm of E0 or E85 gained more weight per gram of food consumed during the 12 days of exposure than did controls. Fuel vapors did not affect litter size or weight, or postnatal weight gain in the offspring. Tests of motor activity and a functional observational battery (FOB) administered to the offspring between post-natal day (PND) 27-29 and PND 56-63 revealed an increase in vertical activity counts in the 3000- and 9000-ppm groups in the E85 experiment on PND 63 and a few small changes in sensorimotor responses in the FOB that were not monotonically related to exposure concentration in any experiment. Neither cell-mediated nor humoral immunity were affected in a concentration-related manner by exposure to any of the vapors in 6-week-old male or female offspring. Systematic concentration-related differences in systolic blood pressure were not observed in rats tested at 3 and 6 months of age in any experiment. No systematic differences were observed in serum glucose or glycated hemoglobin A1c (a marker of long-term glucose homeostasis). These observations suggest a LOEL of 3000 ppm of E85 for vertical activity, LOELs of 9000 ppm of ED and E85 for maternal food consumption, and NOELs of 9000 ppm for the other endpoints reported here. The ethanol content of the vapors did not consistently alter the pattern of behavioral, immunological, or physiological responses to the fuel vapors. The concentrations of the vapors used here exceed by 4-6 orders of magnitude typical exposure levels encountered by the public. Published by Elsevier Inc.