experience notable discomfort, irritation, or certain asymptomatic, non-sensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure.

AEGL-2 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape.

AEGL-3 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience life-threatening health effects or death.


Airborne concentrations below the AEGL-1 represent exposure levels that could produce mild and progressively increasing but transient and nondisabling odor, taste, and sensory irritation or certain asymptomatic, non-sensory effects. With increasing airborne concentrations above each AEGL, there is a progressive increase in the likelihood of occurrence and the severity of effects described for each corresponding AEGL. Although the AEGL values represent threshold levels for the general public, including susceptible subpopulations, such as infants, children, the elderly, persons with asthma, and those with other illnesses, it is recognized that individuals, subject to idiosyncratic responses, could experience the effects described at concentrations below the corresponding AEGL.

SUMMARY

1,2-Dichloroethene is a flammable, colorless liquid existing in both cis-and trans- forms and as a mixture of these two isomers. It is one of a number of two carbon chlorocarbons produced in a reaction mixture resulting from processes involved in the chlorination of ethylene to produce chlorinated monomers and solvents. The trans-isomer is commercially isolated by distillation and sold as a highly purified product that is used in precision cleaning of electronic equipment. The compound is a narcotic. Data on narcosis in humans, cats, rats, and mice, and systemic effects in cats, rats, and mice were available for development of AEGLs. The data were considered adequate for derivation of the three AEGL classifications.

The AEGL-1 was based on human exposure to 825 ppm trans-1,2-dichloroethene for 5 min (Lehmann and Schmidt-Kehl 1936). This concentration is a no-effect-level for eye irritation. This value was divided by an uncertainty factor of 3 to protect sensitive individuals and is considered sufficient because using the default value of 10 for intraspecies variability would generate AEGL-1 values which are not supported by the total data set. (Using the full uncertainty factor of 10, yields an AEGL-1 value of 83 ppm; no effects were noted in humans exposed to 275 ppm). This uncertainty factor of 3 was applied for AEGL-1 values for both the cis- and trans-isomers. Since data suggest that the cis- isomer is approximately twice as toxic as the trans-isomer with regard to narcosis and



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