Benzo[a]fluoren

TERRESTRIAL FATE: Based on a classification scheme(1), an experimental Koc value of 2.88X10+5(1) indicates that benzo(a)fluorene is expected to be immobile in soil(SRC). Volatilization of benzo(a)fluorene from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 1.54X10-6 atm-cu m/mole(SRC), derived from its vapor pressure, 2.43X10-7 mm Hg(3), and water solubility, 0.045 mg/L(4). In addition, adsorption to soil is expected to attenuate potential volatilization(SRC). Benzo(a)fluorene is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure. Polycyclic aromatic hydrocarbons (PAHs), such as benzo(a)fluorene, with more than 3 rings appear to be extremely stable to biodegradation(5). Breakdown in soil generally takes weeks to months for PAHs with 3 rings, primarily by action of microorganisms; PAHs with 4 or more rings are generally resistant to biodegradation(6,7). Benzo(a)fluorene absorbs light strongly at wavelengths >290 nm(8) and, therefore, is expected to be susceptible to direct photolysis on soil surfaces exposed to sunlight(SRC).

AQUATIC FATE: Based on a classification scheme(1), an experimental Koc value of 2.88X10+5(1) indicates that benzo(a)fluorene is expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon an estimated Henry's Law constant of 1.5X10-6 atm-cu m/mole(SRC), derived from its vapor pressure, 2.43X10-7 mm Hg(4), and water solubility, 0.045 mg/L(5). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 35 and 260 days, respectively(SRC). However, volatilization from water surfaces is expected to be attenuated by adsorption to suspended solids and sediment in the water column. The estimated volatilization half-life from a model pond is >10 years if adsorption is considered(6). According to a classification scheme(7), an estimated BCF of 2600(SRC), from a log Kow of 5.68(8) and a regression-derived equation(9), suggests the potential for bioconcentration in aquatic organisms is very high, provided the compound is not metabolized by the organism(SRC). However, benzo(a)fluorene may not bioconcentrate in aquatic organisms which contain microsomal oxidase, such as fish, as this enzyme enables the rapid metabolism of certain polycyclic aromatic hydrocarbons(10). Polycyclic aromatic hydrocarbons (PAHs) with four or more rings, such as benzo(a)fluorene, are generally expected to be resistant to biodegradation(11,12). Hydrolysis is not expected to be an important environmental fate process since this compound lacks functional groups that hydrolyze under environmental conditions(3). Benzo(a)fluorene absorbs strongly at wavelengths >290 nm(13), and therefore is expected to be susceptible to direct photolysis at water surfaces exposed to sunlight(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), benzo(a)fluorene, which has a vapor pressure of 2.43X10-7 mm Hg at 25 °C(2) will exist in both the vapor and particulate phases in the ambient atmosphere. Ambient air monitoring has detected benzo(a)fluorene in both the vapor and particulate phases(3). Vapor-phase benzo(a)fluorene is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 8.3 hours(SRC), calculated from its rate constant of 4.7X10-11 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(3). Particulate-phase benzo(a)fluorene may be removed from the air by wet and dry deposition(SRC). Benzo(a)fluorene absorbs strongly at wavelengths >290 nm(5) and, therefore, is expected to be susceptible to direct photolysis by sunlight(SRC).

Mean benzo(a)fluorene concentrations of 0.2-3.3 ug/kg (fresh wt) were detected in lettuce grown at sites near highways in Sweden(1); results of the monitoring study suggested that food plants grown near highways with high volumes of traffic may become contaminated with PAHs released from vehicle exhaust(1). Benzo(a)fluorene concentrations of 17-28 and 1-2 ug/kg were detected in beef patties grilled over mesquite wood fire and hardwood charcoal respectively(2). Six olive oils and seven virgin olive oils (most consumed in Itlay) were analyzed for PAHs, and benzo(a)fluorene concentrations of 2-27 ug/kg were detected in two olive oils, but was not detected in any other(3).

IDENTIFICATION AND USE: Benzo(a)fluorene is a polycyclic aromatic hydrocarbon (PAH). It does not have a commercial use, other than in biochemical research of PAH. HUMAN STUDIES: Benzo(a)fluorene is present as a minor component of the total content of polynuclear aromatic compounds in the environment. Human exposure to benzo(a)fluorene occurs primarily through the smoking of tobacco, inhalation of polluted air and by ingestion of food and water contaminated with combustion products. ANIMAL STUDIES: Benzo(a)fluorene was tested for carcinogenicity in mice in one study by skin application and in a mouse-skin initiation-promotion assay. Negative results were obtained in both studies. In a study involving subcutaneous administration of benzo(a)fluorene to mice, no injection-site tumor was observed. The available data were inadequate to evaluate the mutagenicity of benzo(a)fluorene to Salmonella typhimurium. ECOTOXICITY STUDIES: Benzo(a)fluorene is a known aryl hydrocarbon receptor (AhR) agonist.

/AQUATIC SPECIES/ In the present study, effect-directed analysis was used to identify teratogenic compounds in porewater collected from a Superfund site along the Elizabeth River estuary (VA, USA). Zebrafish (Danio rerio) exposed to the porewater displayed acute developmental toxicity and cardiac teratogenesis, presumably because of elevated sediment levels of polycyclic aromatic hydrocarbons (PAHs) from historical creosote use. Pretreatment of porewater with several physical and chemical particle removal methods revealed that colloid-bound chemicals constituted the bulk of the observed toxicity. Size-exclusive chromatography and normal-phase high-performance liquid chromatography were used to fractionate Elizabeth River porewater. Acute toxicity of porewater extracts and extract fractions was assessed as the pericardial area in embryonic zebrafish. The most toxic fraction contained several known aryl hydrocarbon receptor (AhR) agonists (e.g., 1,2-benzofluorene and 1,2-benzanthracene) and cytochrome P450 A1 (CPY1A) inhibitors (e.g., dibenzothiophene and fluoranthene). The second most toxic fraction contained known AhR agonists (e.g., benzo[a]pyrene and indeno[1,2,3-cd]pyrene). Addition of a CYP1A inhibitor, fluoranthene, increased toxicity in all active porewater fractions, suggesting synergism between several contaminants present in porewaters. The results indicate that the observed acute toxicity associated with Elizabeth River porewater results from high concentrations of AhR agonistic PAHs and mixture effects related to interactions between compounds co-occurring at the Elizabeth River site. However, even after extensive fractionation and chemical characterization, it remains plausible that some active compounds in Elizabeth River porewater remain unidentified.

See Effects of long-term or repeated exposure.

Redness. Pain.

Benzo(a)fluorene has been identified in gasoline engine exhaust at concentrations of 82-136 ug/L fuel(1). Gaseous emissions from gasoline-powered chain saws had benzo(a)fluorene concentrations ranging from 2.6-16 ug/cu m(2). Two turbine engine exhaust had benzo(a)fluorene levels of 3.31 and 16.19 ng/cu m(3). Benzo(a)fluorene was qualitatively identified in effluents from biomass gasifiers(4).

URBAN/SUBURBAN: Year-round ambient air sampling conducted in Japan in 1977-1978 detected benzo(a)fluorene + benzo(b)fluorene concentrations of 2.40-15.7 ng/cu m in the vapor-phase and 0.15-4.28 ng/cu m in the particulate-phase(1). Air samples collected in Antwerp, Belgium in 1974-1975 contained benzofluorene concentrations of 1.60 ng/cu m in the summer and 19.69 ng/cu m in the winter(2). Air sample collected over an urban area of the Northern Chesapeake Bay in June 1996 contained a benzofluorene concentration of about 0.4-0.5 ng/cu m(3). Benzo(a)fluorene was detected in Chicago, IL urban air samples collected in 1994-1995 (concentration not reported)(4).

INDOOR AIR: Analysis of wood-heated sauna air identified benzo(a)fluorene in both the vapor and particulate phases with concentrations ranging from 0.2-34 ug/cu m(1).

RURAL/REMOTE: Air samples collected in Botrange, Belgium in 1974-1975 contained benzofluorene concentrations of 0.82 ng/cu m in the summer and 2.36 ng/cu m in the winter(1). Samples of sea air collected near Ostend, Belgium in 1974-1975 contained benzofluorene concentrations of 10.21 ng/cu m in the winter(1).

SOURCE DOMINATED: Inhalable air particulate matter collected in Bahrain during July-Aug 1991 during the burning of oil fields in Kuwait contained benzo(a)fluorene concentrations of <0.05 ng/cu m(1).

/OTHER TOXICITY INFORMATION/ Benzo(a)fluorene is present as a minor component of the total content of polynuclear aromatic compounds in the environment. Human exposure to benzo(a)fluorene occurs primarily through the smoking of tobacco, inhalation of polluted air and by ingestion of food and water contaminated with combustion products.