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, 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 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

Furan is a colorless, highly flammable liquid with a strong, ethereal odor. It is used primarily as an industrial intermediate. Occupational exposure to furan is limited because it is handled in closed containers and is used in a closed system in industrial processes. The general public is typically exposed to furan on a daily basis. The chemical has been detected in cooked foods, the gas-phase component of cigarette smoke, wood smoke, exhaust gas from diesel and gasoline engines, and oils obtained by distilling rosin-containing pine wood. If furan is released, it is predicted to exist almost entirely in the vapor phase in the atmosphere because of its relatively high vapor pressure.

Quantitative toxicology data on effects after inhalation exposure to furan were limited to one study in rats. Oral administration of furan resulted in hepatocarcinogenicity and toxicity, and a number of studies determined that a reactive metabolite was responsible for most of the hepatic effects furan induced. In particular, metabolism studies indicate that furan is bioactivated in the liver to a reactive metabolite, cis-2-butene-1,4-dial, by cytochrome P-450 2E1. On the basis of a chronic oral carcinogenicity study in which clear evidence of carcinogenicity was noted in male and female rats and mice, the National Toxicology Program (NTP) classifies furan as “reasonably anticipated to be a human carcinogen” and the International Agency for Research on Cancer (IARC) lists furan as a Group 2B carcinogen (possibly carcinogenic to humans). The U.S. En-



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