Heptacosane

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 3.9X10+7(SRC), determined from a structure estimation method(2), indicates that heptacosane is expected to be immobile in soil(SRC). Volatilization of heptacosane from moist soil surfaces is expected(SRC) given an estimated Henry's Law constant of 655 atm-cu m/mole(SRC), developed using a fragment constant estimation method(2). However, adsorption to soil is expected to attenuate volatilization(SRC). Heptacosane is not expected to volatilize from dry soil surfaces(SRC) based upon an extrapolated vapor pressure of 2.81X10-7 mm Hg at 25 °C(3). Biodegradation oxygen consumption values of 8.2 and 7.6 ug/mL for analogous tetracosane (C24) and hexatriacontane (C36), respectively, using a soil suspension(4) indicate that biodegradation of heptacosane may be a slow environmental fate process in soil(SRC).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 3.9X10+7(SRC), determined from a structure estimation method(2), indicates that heptacosane 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 655 atm-cu m/mole(SRC), developed using a fragment constant estimation method(2). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 5.7 hours and 7.7 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 more than 2 years if adsorption is considered(4). According to a classification scheme(5), an estimated BCF of 8(SRC), from an estimated log Kow of 13.60(2), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Biodegradation oxygen consumption values of 8.2 and 7.6 ug/mL for analogous tetracosane (C24) and hexatriacontane (C36), respectively, using a soil suspension(6) indicate that biodegradation of heptacosane may be a slow environmental fate process in water(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), heptacosane, which has an extrapolated vapor pressure of 2.81X10-7 mm Hg at 25 °C(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase heptacosane 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 11 hours(SRC), calculated from its rate constant of 3.5X10-11 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(3). Particulate-phase heptacosane will be removed from the atmosphere by wet and dry deposition(SRC). Heptacosane does not contain chromophores that absorb at wavelengths >290 nm(4) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC).

IDENTIFICATION AND USE: Heptacosane is a higher n-alkane containing 27 carbon atoms (C27). HUMAN EXPOSURE AND TOXICITY: There are no data available. ANIMAL STUDIES: A homologous series of n-alkanes ranging from n-C12-n-C31 was found in all samples of liver, heart, kidneys, muscle and adipose bovine tissues.

Heptacosane detections in plants used in food and medicinal applications(1). /Heptacosane/[Table#8379]

n-Heptacosane detections in plants used in food and medicinal applications(1).

Heptacosane was found in several species of wasps, including Dolichovespula maculata and Vespula maculifrons; it was the major hydrocarbon at 14% in Vespula squamosa(1). The compound was found in the cuticular surface lipids of the cockroaches Leucophaea maderae and Blatta orientalis(2). Heptacosane was found in several species of fireflies including Lucidota atra, Photuris lucicrescens and Photuris cinctipennis(3).

Alkanes (C20-C32) were the most abundant trace organic compounds found in particulate matter from vehicle exhaust with emission factors for heptacosane from diesel driven light-duty vehicles of 1.76-35.4 ug/km(1). Heptacosane was detected in the gas and particle phase of tailpipe emissions from non-catalyst equipped gasoline powered motor vehicles at concentrations of 2.4 and 391 ug/km, respectively(2).

Using a structure estimation method based on molecular connectivity indices(1), the Koc of heptacosane can be estimated to be 3.9X10+7(SRC). According to a classification scheme(2), this estimated Koc value suggests that heptacosane is expected to be immobile in soil.

Heptacosane has been detected in various parts of a least 20 varieties of plants(1). Heptacosane was found in several species of wasps including Dolichovespula maculata, Vespula squamosa and Vespula maculifrons(2). Heptacosane was found in the cuticular surface lipids of the cockroaches: Leucophaea maderae and Blatta orientalis(3). Heptacosane was found in several species of fireflies including Lucidota atra, Photuris lucicrescens and Photuris Cinctipennis(4).

URBAN/SUBURBAN: Heptacosane was detected in particulate air samples from Georgia Tech campus, GA at mean concentrations of 1.96 and 1.82 ng/cu m for summer 2005 and winter 2006, respectively(1). A mean heptacosane concentration of approximately 22 ng/cu m was reported in the particulate phase of air samples collected in an urban and industrialized area in Prato, Italy during 2002(2). Heptacosane concentration was 11.9 and 8.5 ng/cu m in particulate phase in the summer and winter, respectively; the concentration was 3.1 and 1.0 ng/cu m in the vapor phase in summer and winter, respectively; samples were collected in an urban area in Nagoya, Japan in 1991(3).

RURAL/REMOTE: Heptacosane was detected in particulate air samples from a rural area of Yorkville, GA at mean concentrations of 0.40 and 1.33 ng/cu m for summer and winter, respectively(1).

SOURCE DOMINATED: Heptacosane was detected at 140-1260 pg/cu m with a mean of 480 pg/cu m in particulate air samples collected near a highway in Raleigh, NC; concentrations in samples collected 275 meters from the highway contained 190-2000 pg/cu m with a mean of 490 pg/cu m(1). Heptacosane was detected in particulate air samples from an interstate highway in Georgia at a mean concentration of 2.69 and 2.56 ng/cu m for summer and winter, respectively(2).

AEROBIC: Oxygen consumption of 8.2 and 7.6 ug/mL over 10 days was reported for straight chain alkanes tetracosane (C24) and hexatriacontane (C36), respectively, using a soil suspension of Hudson-Collamer silt loam soil incubated in the dark at 25 °C(1). By analogy, these test results suggest that biodegradation rates are slow for long chain alkanes such as heptacosane (C27) under these conditions(SRC).

PURE CULTURE: Using 5 different marine bacterial strains and 4 different nitrogen sources, biodegradation of petroleum oil was examined under aerobic conditions at 26 °C for 10 days. Data reported for similar long chain alkanes, hexacosane (C26), octacosane (C28), and triacontane (C30), which were present as components of the petroleum oil, indicate that these compounds were degraded by 4 of 5 bacterial strains with certain nitrogen sources, and consumption ranged from 5 to 96%(1).