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 concentrations that could produce mild and progressively increasing but transient and nondisabling odor, taste, and sensory irritation or certain asymptomatic, nonsensory 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 concentrations 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

Chlorobenzene is a flammable liquid with a high vapor pressure and a water solubility of 50 milligrams per liter (mg/L) at 20°C. It is used as a solvent and in the production of nitrochlorobenzene and intermediates for the synthesis of dyestuffs, pharmaceuticals, and products for the rubber and plastic industries. Chlorobenzene has an aromatic, almond-like odor. The odor threshold is 0.050 mg/L in water and is 0.2-1.8 ppm in air, although a value of 62 ppm has also been reported for air.

The toxicity database on chlorobenzene is poor. Information often had to be obtained from descriptions in reviews and summaries, and some older literature could not be obtained (e.g., Rozenbaum et al. [1947]). Human data include to two kinetic studies with volunteers. Animal data included studies on teratogenicity, reproductive toxicity, and mortality. A few studies with experimental animals addressing central nervous system (CNS) depression were reviewed, but were difficult to interpret.

AEGL-1 values are based on kinetic studies with volunteers. Effects in subjects exposed to chlorobenzene at 60 ppm for 7 h (with a 1-h break after 3 h) are indicative of slight CNS depression (drowsiness, heavy head, and headache) and local irritation (Ogata et al. 1991), and are considered evidence of discomfort. These effects were not observed is subjects exposed at 10 ppm for 8 h



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