Carcinogenicity

Furan is reasonably anticipated to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in experimental animals.

Properties

Furan is a cyclic dienic ether that is a clear, colorless liquid with an ethereal odor (Akron 2009; HSDB 2009). It can turn brown upon standing (HSDB 2009). Furan is slightly soluble in water and is soluble at greater than 10% in acetone, benzene, ether, and ethanol. It is extremely flammable and may form explosive peroxides in the absence of inhibitors (Akron 2009). Physical and chemical properties of furan are listed in Table 1.

Table 1

Properties of Furan.

Use

Furan is used primarily as an intermediate in the synthesis and production of tetrahydrofuran, pyrrole, and thiophene. Hydrogenation of furan over a nickel catalyst produces high yields of tetrahydrofuran and is a source of commercial tetrahydrofuran (IARC 1995; NTP 1993). Furan is also used in the formation of lacquers, as a solvent for resins, and in the production of agricultural chemicals, stabilizers, and pharmaceuticals (HSDB 2009; IARC 1995).

Production

Commercial production of furan involves decarbonylation of furfural over a palladium-charcoal catalyst. The commercial product is at least 99% pure (IARC 1995). U.S. production of furan was between 10 and 50 million pounds from 1986 to 1998 (EPA 2004), but combined production and imports had fallen to between 1 million and 10 million pounds by 2014 (EPA 2016). In 1986, U.S. imports of furan resins totaled about 9.7 million pounds (HSDB 2009). No information on U.S. imports and exports of furan was found. In 2009, furan was available from 20 suppliers worldwide, including 11 U.S. suppliers (ChemSources 2009).

Exposure

Evidence that the U.S. general population is exposed to furan comes from findings of furan in human blood and exhaled breath. The 2013–2014 National Health and Nutrition Examination Survey (NHANES) found that the 95th-percentile concentration of furan in whole blood was 0.091 ng/mL, based on a sample of 3,203 individuals of all ages, both genders, and all race and ethnicity groups (CDC 2018a). People are exposed to furan primarily through ingestion of food, inhalation of contaminated air, and tobacco smoking. The pattern of commercial use suggests that minimal exposure to the general population would be expected through contact with products contaminated with furan (NTP 1993). However, furan can be formed in foods during processing.

Furan was measured by the U.S. Food and Drug Administration in various foods and beverages, including infant formulas, baby foods, soups and sauces, fruits and vegetables, bread, and meat products. The maximum concentration found was 125 ppb (μg/kg) in canned soup (FDA 2005). A second study confirmed that heat-treated foods, such as canned and jarred foods, contained measurable quantities of furan (up to 240 μg/kg in canned chili) (Becalski et al. 2005). Furan was measured in fruit juice at concentrations near 1 μg/kg (Goldmann et al. 2005). In several brands of brewed coffee, the highest furan concentration found was 84.2 ppb (FDA 2005; Ho et al. 2005). Furan was also identified as a component of coffee aroma that has antioxidant activity (Fuster et al. 2000). Furan was also detected at a concentration of 110 μg/kg in jarred baby food containing cooked vegetables (Goldmann et al. 2005). However, furan concentrations decreased after the jar was opened and the contents were heated. When food is heated in a container, furan concentrations increase if the container remains closed, but not if it is open (Hasnip et al. 2006). Furan does not appear to be transferred from the packaging or gasket of the can or jar. Furan is formed from ascorbic acid, fructose, sucrose, and glucose when foods are heated or irradiated (Fan 2005). Furan production increases greatly with decreasing pH of the medium; 1,600 times as much furan is formed at pH 3 as is formed at pH 8.

Furan is found at higher levels in the blood and exhaled breath of smokers than in the general population. The 2013–2014 NHANES found that in a sample of 951 cigarette smokers of all ages and both genders, the 95th-percentile concentration in whole blood was 0.172 ng/mL (CDC 2018b). In one study in Texas, furan was detected in the exhaled breath of two of three male smokers and four of five male nonsmokers (HSDB 2009). Smokers exhaled between 0.25 and 98 μg of furan per hour, and nonsmokers exhaled between 0.33 and 28 μg/h. In a study in Chicago, 15 of 387 breath samples collected from 54 male and female nonsmokers had detectable levels of furan, with a mean concentration of 0.55 ng/L. Furan was also detected in the indoor air of homes in the Chicago, Illinois, and Washington, D.C., metropolitan areas (NTP 1999). Furan also occurs naturally in pine rosin and in volatile emissions from sorb trees (HSDB 2009).

The primary route of occupational exposure to furan is inhalation. The industrial processes in which furan is used are conducted in closed systems, and its volatility requires that furan be handled in closed containers; therefore, occupational exposure is limited (NTP 1993). The National Occupational Hazard Survey (conducted from 1972 to 1974) estimated that 244 workers potentially were exposed to furan (NIOSH 1976). The National Occupational Exposure Survey (conducted from 1981 to 1983) estimated that 35 workers (mostly in the Business Services industry), including 7 women, potentially were exposed to furan (NIOSH 1990).

Regulations

Guidelines

References

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