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 can 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 levels for the general public, including sensitive subpopulations, such as infants, children, the elderly, persons with asthma, and those with other illnesses, it is recognized that certain individuals, subject to unique or idiosyncratic responses, could experience the effects described at concentrations below the corresponding AEGL.
Nickel carbonyl, formed by the reaction of carbon monoxide with metallic nickel, is used in nickel refining, in the synthesis of acrylic and methacrylic esters, and for other organic synthesis. In air, nickel carbonyl rapidly decomposes to metallic nickel and carbon monoxide with a 50% decomposition at room temperature and total decomposition at 150-200 C. Its decomposition is inversely proportional to the concentration of carbon monoxide; in the absence of carbon monoxide, decomposition may occur in approximately 1 min. Thus, potential exposure to the parent nickel carbonyl is limited by its rapid conversion to airborne metallic nickel.
Human data are limited to case reports, primarily of nickel workers, that affirm the extreme toxicity of the compound. Definitive exposure terms are lacking in these reports. Available information suggests that there are very limited or no warning properties associated with exposure to nickel carbonyl. Significant signs and symptoms of toxicity are known to occur in the absence of recognizable odor. Human case studies have shown that a latency period often occurs between initial signs of toxicity and subsequent serious effects that may progress to death. The primary target of nickel carbonyl-induced acute toxicity appears to be the lungs, although extra pulmonary involvement also has been reported. The specific mechanism of toxicity is unclear but appears to involve damage to pulmonary tissue.
Animal data are limited to lethality and developmental toxicity. Lethality values (LC50) are available for rats, mice, cats, and rabbits. Thirty-minute LC50