predicted that the general population, including susceptible individuals, could experience notable discomfort, irritation, or certain asymptomatic, nonsensory 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 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 AEGLs represent threshold levels for the general public, including sensitive subpopulations, it is recognized that certain individuals, subject to idiosyncratic responses, could experience the effects described at concentrations below the corresponding AEGL.

SUMMARY

Acetone cyanohydrin is a colorless to yellowish liquid with a characteristic bitter almond odor due to the presence of free hydrogen cyanide (HCN). The major use of acetone cyanohydrin is in the production of ̣methacrylic acid and its esters; the latter are used for the production of plexiglass. Further uses of acetone cyanohydrin are in the production of acrylic esters, polyacrylic plastics. and synthetic resins, as well as in the manufacture of insecticides, pharmaceuticals, fragrances, and perfumes. Acetone cyanohydrin decomposes spontaneously in the presence of water to acetone and HCN.

Fatalities and life-threatening occupational intoxication have been described after accidental inhalation, skin contact, and ingestion. Initial symptoms after mild exposure to acetone cyanohydrin range from cardiac palpitation, headache, weakness, dizziness, nausea, and vomiting to nose, eye, throat, and skin irritation. Acetone cyanohydrin behaves as its molar equivalent in cyanide both in vitro and in vivo. All the pharmacologic actions of cyanide result from cyanide’s reversible complex with the ferric (+3) state of mitochondrial cytochrome c oxidase also known as ferrocytochrome c oxygen oxidoreductase. Cessation of electron transport across the inner mitochondrial membrane results in inhibition of oxygen utilization and causes hypoxia and cellular destruction.

Four studies exposed rats repeatedly to acetone cyanohydrin at about 10, 30, and 60 ppm for 6 h/day (d), 5 d/week (wk) for a total of 4 weeks (Monsanto



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