Naphthalene

CAS RN: 91-20-3

Exposure Summary

Naphthalene's production and use in the manufacture of phthalic anhydride, which is used as an intermediate in the production of phthalate plasticizers, resins, dyes, pharmaceuticals, insect repellents, and other materials may result in its release to the environment through various waste streams. Naphthalene was found in various species marine algae and in cork samples from camphor trees, us found in oak, ash and hazel leaves, and has been detected in needles from Pinus pinea and needles from Pinus pinaster. Naphthalene has been detected in plants such as catnip, saffron, and clove. Naphthalene is also a component of crude oil. The largest releases of naphthalene result from the combustion of wood and fossil fuels or the production of coal tar. If released to air, a vapor pressure of 0.085 mm Hg at 25 deg C indicates naphthalene will exist solely as a vapor in the atmosphere. Vapor-phase naphthalene will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals and with nitrate radicals; the half-lives for these reactions in air are estimated to be 14-16 and 60 hours, respectively. If released to soil, naphthalene is expected to have high to no mobility based upon Koc values of 112 to 9,333, depending on the nature of the soil. Volatilization from moist soil surfaces is expected to be an important fate process based upon a Henry's Law constant of 4.4X10-4 atm-cu m/mole. The estimated volatilization half-life for naphthalene from soil is 1.1 days, and 14 days when incorporated at a depth of 1 cm and 10 cm, respectively. Naphthalene is not expected to volatilize from dry soil surfaces based upon its vapor pressure. In soils previously exposed to naphthalene or other PAHs, half-lives of 2-18 days have been reported, due to biodegradation. If released into water, naphthalene is expected to adsorb to suspended solids and sediment based upon the Koc values. Naphthalene has been shown to biodegrade in water with half-lives ranging from about 0.8 to 43 days. 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 6 hours and 5 days, respectively. BCF values of 36.5-714 suggest bioconcentration in aquatic organisms is moderate to high. Hydrolysis is not expected to be an important environmental fate process since this compound lacks functional groups that hydrolyze under environmental conditions (pH 5 to 9). Photolysis in sunlit surface waters may be an important fate process based upon an aqueous photolysis half-life of 71 hours. Occupational exposure to naphthalene may occur through inhalation and dermal contact with this compound at workplaces where naphthalene is produced or used. The most likely pathway by which the general public is exposed to naphthalene is by inhalation due to the release of this substance from combustion fuels, moth repellents, and cigarette smoke. Monitoring data also indicate that the general population may be exposed to naphthalene via ingestion of food and drinking water, although these pathways are considered minor when compared to inhalation. (SRC)
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