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 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.
Vinyl chloride (VC) is a colorless, flammable gas with a slightly sweet odor. It is heavier than air and accumulates at the bottom of rooms and tanks. Worldwide production of VC is approximately 27,000,000 tons. Most VC is polymerized to polyvinyl chloride. Combustion of VC in air produces carbon dioxide and hydrogen chloride. Odor thresholds of VC range from 10 to 25,000 ppm. Validated studies that provide quantitative data on odor recognition and detection are not available; therefore, a level of odor awareness (LOA) could not be derived.
VC is an anesthetic compound. After a 5-min exposure to VC at 16,000 ppm, volunteers experienced dizziness, lightheadedness, nausea, and visual and auditory dulling (Lester et al. 1963). Mild headache and some dryness of the eyes and nose were the only complaints of volunteers exposed at 491 ppm for several hours (Baretta et al. 1969). No data on the developmental or reproductive toxicity of VC in humans after acute exposure are available. Chromosomal aberrations in human lymphocytes were associated with accidental exposure to VC. After chronic occupational exposure, VC is a known human carcinogen that induces liver angiosarcoma, possibly hepatocellular carcinoma, and brain tumors. Evidence of tumors at other sites is contradictory. Two epidemiologic studies (Mundt et al. 2000; Ward et al. 2001) found no increase in standardized mortality ratios (SMRs) after 5 years of occupational exposure to VC, whereas a third study suggested an increase after 1-5 years of exposure (Boffetta et al. 2003).