Chlorine

CAS RN: 7782-50-5

Exposure Summary

Chlorine's production and use in the manufacture of chemicals, as an oxidizing and bleaching agent, and as a water disinfectant may result in its release to the environment through various waste streams. Scientists have proposed that minute quantities of chlorine are generated naturally during the photolysis of seawater aerosols. Volcanic gases can contain free chlorine gas. If released to air, a vapor pressure of 5850 mm Hg at 25 deg C indicates chlorine will exist solely as a gas in the atmosphere. Gas-phase chlorine is removed from air primarily by direct photolysis with an estimated half-life of 1-4 hours, depending on the time of the day. Chlorine is also expected to react with cloud particulates and rain drops that it comes into contact with in the atmosphere, forming hydrochloric and hypochlorous acids. These acids can then be washed out of the atmosphere by precipitation. If released to soil in a spill situation as a liquid, chlorine will react with both organic and inorganic matter in the soil and much of the chlorine is expected to volatilize immediately. Chlorine is expected to dissolve and disproportionate in the water of moist soils to form chloride and hypochlorite. Chlorine is toxic to microbial communities; therefore, biodegradation is not considered to be a relevant fate process in soil and water. If released into water, chlorine gas dissolves and then undergoes a disproportionation within seconds at environmental pH to form hydrochloric and hypochlorous acid. Under acidic conditions (pH <4.5), the formation of molecular chlorine is possible. Volatilization of molecular chlorine from water surfaces is expected to be an important fate process based upon a Henry's Law constant of 0.0104 atm-cu m/mole. Chlorine is not expected to bioaccumulate or bioconcentrate in plants or animals since it reacts with the moist tissues of living systems. In water chlorine/hypochlorite undergoes direct photolysis with an estimated half-life of 1-4 hours, depending on the time of the day. Occupational exposure to chlorine may occur through inhalation and dermal contact with this compound at workplaces where chlorine is produced or used. The general population may be exposed to chlorine via inhalation and dermal contact as a result of an accident involving chlorine that occurs nearby, such as a liquid chlorine spill, a leak from a chlorine tank, or a leak from a facility that produces or uses chlorine. Individuals may be exposed to chlorine upon mixing a cleaning product that contains an acid with a solution containing sodium hypochlorite (bleach). The misuse of swimming pool chemicals may also potentially expose the general population to chlorine. The general public is not exposed to molecular chlorine in drinking water as a result of water sanitation practices, even though chlorine gas may be used in these processes. Because chlorine is so reactive in water and air, it is not normally detected in the environment except for very low levels in the air above seawater. (SRC)
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