Toxicity evaluation of petroleum blending streams: inhalation subchronic toxicity/neurotoxicity study of a light catalytic cracked naphtha distillate in rats

Laminar Flame Speed, Ignition Delay Time, and CO Laser Absorption Measurements of a Gasoline-like Blend of Pentene Isomers

The combustion properties of a gasoline-like blend of pentene isomers were determined using multiple types of experimental measurements. The representative mixture (Mix A) is composed of 5.7% 1-pentene (1-C₅H₁₀), 39.4% 2-pentene (2-C₅H₁₀), 12.5% 2-methyl-1-butene (2M1B), and 42.4% 2-methyl-2-butene (2M2B) (% mol). Laminar flame speeds were measured at equivalence ratios of 0.7-1.5 in a constant-volume combustion chamber, and ignition delay times (including both OH* and CH* diagnostics) as well as CO time-history profiles were performed in shock tubes, in highly diluted mixtures (0.995 He/Ar), at a stoichiometric condition for temperatures ranging from 1350 to 1750 K, and at near-atmospheric pressure. Two additional unbalanced mixtures removing either 2M2B (Mix B) or 2-C₅H₁₀ (Mix C) were studied in a shock tube to collect CO time histories, representing the most stringent validation constraints, as these two pentenes constitute the biggest proportions in Mix A and exhibit opposite behaviors in terms of reactivity due to their chemical structure differences. Numerical predictions using a recent validated chemical kinetics mechanism encompassing all pentene isomers from Grégoire et al. ( Fuel2022, 323, 124223) are presented. The use of a complex blend of four pentene isomers in the present paper provided a capstone test of the current mechanism's ability to model pentene-isomer combustion chemistry, with very good results that reflect positively on the current state of the art in pentene isomer kinetics modeling.

Gasoline toxicology: overview of regulatory and product stewardship programs

Significant efforts have been made to characterize the toxicological properties of gasoline. There have been both mandatory and voluntary toxicology testing programs to generate hazard characterization data for gasoline, the refinery process streams used to blend gasoline, and individual chemical constituents found in gasoline. The Clean Air Act (CAA) (Clean Air Act, 2012: § 7401, et seq.) is the primary tool for the U.S. Environmental Protection Agency (EPA) to regulate gasoline and this supplement presents the results of the Section 211(b) Alternative Tier 2 studies required for CAA Fuel and Fuel Additive registration. Gasoline blending streams have also been evaluated by EPA under the voluntary High Production Volume (HPV) Challenge Program through which the petroleum industry provide data on over 80 refinery streams used in gasoline. Product stewardship efforts by companies and associations such as the American Petroleum Institute (API), Conservation of Clean Air and Water Europe (CONCAWE), and the Petroleum Product Stewardship Council (PPSC) have contributed a significant amount of hazard characterization data on gasoline and related substances. The hazard of gasoline and anticipated exposure to gasoline vapor has been well characterized for risk assessment purposes.

Toxicological Assessment of Heavy Straight Run Naphtha in a Repeated Dose/Reproductive Toxicity Screening Test

Gasoline blending stocks (naphthas) are comprised of normal, iso- and cycloparaffins and aromatic hydrocarbons with carbon numbers ranging from C4 to C12. Heavy straight run naphtha (HSRN, CAS number 64741-41-9) was selected for toxicity screening because substances of this type contain relatively high levels (28%) of cycloparaffins by comparison to other naphtha streams and the data complement toxicity information on other gasoline blending streams. Rats were exposed by inhalation to wholly vaporized material at levels of approximately 100, 500, or 3000 parts per million (ppm) daily to screen the potential for systemic toxicity, neurotoxicity, reproductive toxicity, and developmental effects to postnatal day 4. All animals survived the treatment period. Principal effects of repeated exposure included increased liver weights in males and females, increased kidney weights in males, and histological changes in the thyroid, secondary to liver enzyme induction. These changes were not considered to be toxicologically meaningful and are not relevant to humans. There were no treatment-related effects in functional observation tests or motor activity; no significant reductions in fertility or changes in other reproductive parameters; and no evidence of developmental toxicity in offspring. The overall no observed adverse effect concentration was 3000 ppm (approximately 13 600 mg/m3). In conclusion the HSRN effects on liver and kidney are consistent with the results of other studies of volatile fractions or other naphthas or formulated gasoline, and there were no HSRN effects on neurological developmental or reproductive parameters.

Nasal epithelial lesions in F344 rats following a 90-day inhalation exposure to naphthalene

Naphthalene (NA) was shown to be carcinogenic, causing respiratory epithelial adenoma in the nasal cavity of male F344 rats and olfactory epithelial neuroblastoma in female F344 rats at exposure concentrations of 10-60 ppm in a 2-year inhalation study conducted by the National Toxicology Program. To explore the exposure-response relationship and threshold for nasal epithelial effects in F344 rats, a 90-day (6 h/d, 5 d/wk) inhalation study was conducted at 0, 0.1, 1, 10 and 30 ppm NA vapor. Group size for nasal cavity histopathology was 10/sex with an additional 10/sex evaluated 4 wk post-exposure. NA exposure concentrations were measured by GC/MS, and aerosol testing verified that solid NA particles were not present. There were no NA exposure-related clinical observations and mild decreases in body weight (<10%) and food/water consumption were observed primarily in the 30 ppm rats. Rat heads were cross-sectioned at six levels for microscopic examination. There were no nasal cavity lesions related to NA exposure in rats of the 0.1 ppm group. Minimal hyperplasia was observed in the transitional/respiratory epithelium of rats exposed to 1 ppm. Mild hyperplasia and minimal squamous metaplasia were observed in the respiratory epithelium of rats exposed to 10 or 30 ppm. Lesions in the olfactory epithelium were observed only in rats of the 10 or 30 ppm groups and consisted of degeneration, necrosis, areas of re-epithelialization and basal cell hyperplasia. There was remarkable recovery of effects after 4 weeks, but residual olfactory epithelial degeneration and basal cell hyperplasia were still evident.

Nasal olfactory epithelial lesions in F344 and SD rats following 1- and 5-day inhalation exposure to naphthalene vapor

The exposure-response relationship and threshold for nasal epithelial effects of naphthalene (NP) vapor in F344 and SD rats were investigated in 1-day (6 hours) and 5-day (6 h/d) studies at concentration ranges of 0 to 30 ppm. Lesions related to 1-day exposure were predominantly necrosis of the olfactory epithelium (OE). The severity of OE lesions was concentration dependent and ranged from minimal (< or =1 ppm) to marked (10-30 ppm). In the 5-day study, degeneration of OE was observed in both strains, both sexes, with increasing incidence and severity that correlated with concentration. The epithelial degeneration lesion was minimal to moderate in severity. At 0.1 ppm, minimal OE lesions were observed in female SD rats only (20% incidence). Animals exposed to 10 ppm NP followed by 14 days without exposure also had OE lesions, but of lower severity, showing evidence of good recovery. In both studies, differences between sex or strain were not remarkable.