2-Xylene

CAS RN: 95-47-6

Exposure Summary

2-Xylene's production and use in the manufacture of chemicals and in gasoline blending may result in its release to the environment through various waste streams. 2-Xylene may be released to the environment through emissions from various fuel industries and through evaporative emissions from fuels such as gasoline. It is emitted to air from burning wood and in motor vehicle exhaust. 2-Xylene occurs naturally in petroleum and coal tar, is released during forest fires and occurs in various plants. If released to air, a vapor pressure of 6.65 mm Hg at 25 deg C indicates 2-xylene will exist solely as a vapor in the atmosphere. Vapor-phase 2-xylene will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals and nitrate radicals; the half-lives for these reaction in air is estimated to be 1.2 and 85 days respectively. 2-Xylene has been detected in rainwater and snow and, therefore, it may be removed from the air by wet deposition. 2-Xylene does not absorb at wavelengths >290 nm and, therefore, is not expected to be susceptible to direct photolysis by sunlight. If released to soil, 2-xylene is expected to have very high to moderate mobility in soil based upon Koc values ranging from 24-251. Volatilization from moist soil surfaces is expected to be an important fate process based upon a Henry's Law constant of 5.18X10-3 atm-cu m/mole. 2-Xylene is expected to volatilize from dry soil surfaces based upon its vapor pressure. 2-Xylene biodegrades in soil under both aerobic and anaerobic conditions. Biodegradation is an important process in subsurface soils and groundwater where volatilization is hindered. Utilizing a standard test (manometric respirometry), 90-94% of the theoretical biodegradation was reached in 4 weeks indicating 2-xylene can be readily biodegradable. However, under anaerobic conditions, a long lag period may be required before degradation commences. If released into water, 2-xylene is not expected to adsorb to suspended solids and sediment based upon the Koc values. 2-Xylene is expected to biodegrade in water under aerobic conditions based on reported half-lives ranging from days to weeks. 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 3.2 hours and 4.1 days, respectively. A BCF of 14 in goldfish indicates that bioconcentration in aquatic organisms is low. 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 2-xylene may occur through inhalation and dermal contact with this compound at workplaces where 2-xylene is produced or used. Monitoring data indicate that the general population may be exposed to 2-xylene via inhalation of ambient air, ingestion of food and drinking water, and dermal contact with consumer products containing 2-xylene. Contact with xylene occurs from a variety of consumer products, including gasoline, paint, varnish, shellac, rust preventives, and cigarette smoke. (SRC)
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