n-Pentane

CAS RN: 109-66-0

Exposure Summary

n-Pentane's production and use as a general laboratory solvent, a solvent for polymerization reactions, and as a raw material in the synthesis of olefins and other industrial chemicals may result in its release to the environment through various waste streams. n-Pentane is also a component of natural gas and crude oil. The vast majority of n-pentane is released to the environment through the manufacture, use, and disposal of many products associated with the petroleum industry and the combustion of gasoline. If released to air, a vapor pressure of 514 mm Hg at 25 deg C indicates n-pentane will exist solely as a vapor in the ambient atmosphere. Vapor-phase n-pentane will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 3 days. n-Pentane does not contain chromophores that absorb at wavelengths >290 nm and, therefore, is not expected to be susceptible to direct photolysis by sunlight. If released to soil, n-pentane is expected to have high mobility based upon an estimated Koc of 72. Volatilization from moist soil surfaces is expected to be an important fate process based upon a Henry's Law constant of 1.25 atm-cu m/mole. n-Pentane may volatilize from dry soil surfaces based upon its vapor pressure. Screening studies suggest that n-pentane will undergo biodegradation in soil and water surfaces, but volatilization is expected to be the predominant fate process in the environment. If released into water, n-pentane is not expected to adsorb to suspended solids and sediment based upon the estimated Koc. Volatilization from water surfaces is expected to be an important fate process based upon this compound's Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 2.5 hrs and 3.4 days, respectively. An estimated BCF of 80 suggests the potential for bioconcentration in aquatic organisms is moderate. Hydrolysis is not expected to be an important environmental fate process since this compound lacks functional groups that hydrolyze under environmental conditions. Occupational exposure to n-pentane may occur through inhalation and dermal contact with this compound at workplaces where n-pentane is produced or used. Monitoring data indicate that the general population may be exposed to n-pentane via inhalation of ambient air, particularly at urban areas with heavy vehicular traffic or gasoline filling stations. (SRC)
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