Ethylene

CAS RN:74-85-1

Exposure Summary

Ethylene's production and use as a chemical intermediate and precursor in industrial organic synthesis, in the welding and cutting of metals, as a refrigerant may result in its release to the environment through various waste streams. Its use as a plant growth regulator will result in its direct release to the environment. Ethylene is a natural product emitted by plants. If released to air, a vapor pressure of 5.21X10+4 mm Hg at 25 deg C indicates ethylene will exist solely as a gas in the atmosphere. Gas-phase ethylene 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 2 days. Ethylene absorbs UV at wavelength 175.2 nm and, therefore, is not expected to be susceptible to direct photolysis by sunlight. If released to soil, ethylene is expected to have very high mobility based upon an estimated Koc of 13. Volatilization from moist soil surfaces is expected to be an important fate process based upon a Henry's Law constant of 0.228 atm-cu m/mole. Ethylene may volatilize from dry soil surfaces based upon its vapor pressure. Biodegradation data in soil or water were not available. However, ethylene was biodegraded to ethylene oxide using acclimated cell free extracts. If released into water, ethylene 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 estimated Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 2 hrs and 2 days, respectively. An estimated BCF of 2.6 suggests the potential for 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 (pH 5 to 9). Occupational exposure to ethylene may occur through inhalation and dermal contact with this compound at workplaces where ethylene is produced or used. Monitoring data indicate that the general population may be exposed to ethylene via inhalation of ambient air and smoking cigarettes. (SRC)
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