Sarin

CAS RN: 107-44-8

Exposure Summary

Sarin's production may result in its release to the environment through various waste streams; its use as a chemical warfare agent and nerve gas will result in its direct release to the environment. If released to air, a vapor pressure of 2.86 mm Hg at 25 deg C indicates sarin will exist solely as a vapor in the atmosphere. Vapor-phase sarin 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 9.6 hours. The UV absorption spectrum of sarin in cyclohexane solution does not exhibit any absorption above 290 nm; therefore, sarin is not expected to degrade through direct photolysis in the environment. If released to soil, sarin is expected to have very high mobility based upon an estimated Koc of 16. The importance of leaching in moist soil will be attenuated due to sarin's ability to hydrolyze in water. Laboratory and field studies have demonstrated that sarin evaporates rapidly from non-absorbing surfaces, even at extremely cold temperatures. Two soil persistence studies conducted by the US Army found that 90% or more of sarin added to soil will be lost in the first five days. Biodegradation data for sarin were not available. If released into water, sarin is not expected to adsorb to suspended solids and sediment based upon the estimated Koc. Hydrolysis will be the major fate process in water. Sarin will degrade through aqueous hydrolysis which is pH and temperature dependent to HF and isopropyl methylphosphonic acid. The fastest rates of hydrolysis occur below pH 4 and above 6.5. In distilled water at 25 deg C, the hydrolysis half-lives range from 75 hr at pH 7 to 0.8 hr at pH 9. The hydrolysis rate increases in seawater due to the catalytic effect of ions; the seawater hydrolysis half-life at pH 7.6 and 25 deg C is about 1 hr. Volatilization from water surfaces occurs slowly. Estimated volatilization half-lives for a model river and model lake are 76 and 555 days, respectively. An estimated BCF of 3 suggests the potential for bioconcentration in aquatic organisms is low. Occupational exposure to sarin may occur through inhalation and dermal contact with this compound at workplaces where sarin is produced or used in demilitarization operations(SRC). Exposure to sarin occurs through vapor contact which is readily absorbable through not only the lungs and eyes but also the skin and intestinal tract. The general population will not be exposed to sarin unless it is used as a weapon; exposure to sarin, if used as a weapon, will be via inhalation of ambient air and dermal contact. (SRC)
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