CAS No. 100-41-4
Ethylbenzene is a flammable hydrocarbon found in crude oil. It is a high production chemical used largely to synthesize styrene and also as a solvent and an additive to automobile and aviation fuels. Automobile emission contributes a significant amount of ethylbenzene to outdoor air. Indoor sources of ethylbenzene include carpet adhesives and tobacco smoke. Ethylbenzene is ubiquitous in ambient air, with higher concentrations in areas with greater vehicular traffic. It undergoes biodegradation or photooxidation in air, water, and soil, and it does not bioaccumulate in aquatic food chains (ATSDR, 2007). Producing and using petroleum products are potential sources of workplace exposure to ethylbenzene.
The general population may be exposed to ethylbenzene through inhalation, particularly from motor vehicle emissions, self-service gasoline pump vapors, and cigarette smoke. Drinking water is contaminated rarely by leaking underground storage tanks containing petroleum products. Ethylbenzene is well absorbed by inhalation, oral, or dermal exposure routes. After absorption, ethylbenzene is metabolized rapidly by the liver. Mandelic and phenylglyoxylic acids are the predominant urinary metabolites and have been used to monitor workplace exposure (Knecht et al., 2000).
Human health effects from ethylbenzene at low environmental doses or at biomonitored levels from low environmental exposures are unknown. Ethylbenzene can cause respiratory tract and eye irritation and dizziness at air concentrations that exceed workplace standards (Cometto-Muniz and Cain, 1995). Much higher levels occurring with accidental exposures can produce central nervous system depression. Laboratory animals exposed to ethylbenzene for several weeks to months at air concentrations several times higher than occupational standards have shown respiratory irritation, increased liver weight, liver microsomal enzyme induction, and increased leukocyte counts (ATSDR, 2010). Chronic animal exposure studies have also demonstrated renal tubular, alveolar, and hepatic tumors with some evidence of gender-specific susceptibility (NTP, 1999).
The IARC classified ethylbenzene as a possible human carcinogen. OSHA and ACGIH established workplace standards and guidelines, respectively, for ethylbenzene. The U.S. EPA established environmental and drinking water standards for ethylbenzene. Information about external exposure (i.e., environmental levels) and health effects is available from ATSDR at http://www.atsdr.cdc.gov/toxprofiles/index.asp.
Levels of ethylbenzene in blood reflect recent exposure. In a nonrepresentative subsample of adults in the National Health and Nutrition Examination Survey (NHANES) III (1988-1994), the median ethylbenzene level in blood was 0.060 µg/L (Ashley et al., 1994), which is similar to the geometric mean value reported for nonsmokers in the NHANES 1999-2000 subsample (Lin et al., 2008). The geometric mean in participants 20 years and older in the NHANES 2001-2002, 2003-2004, and 2005-2006 subsamples appear similar or slightly below these previously reported values, though differences in methodology and sampled populations may account for slight differences in levels. Also, approximately similar levels were observed in sample of southwestern U.S. residents (Buckley et al., 1997), but such levels were about two to three times higher than levels reported among low-income children in a Midwestern U.S. city (Sexton et al., 2005, 2006).
Smoking cigarettes increases blood ethylbenzene levels, but environmental tobacco smoke exposure appears not to increase blood ethylbenzene (Lin et al., 2008; Perbellini et al., 2002). Residents in high density urban areas and commuters may have ethylbenzene levels up to two times higher than the nonsmoking general population (Lemire et al., 2004). Street vendors and workers exposed to gasoline fumes can have blood ethylbenzene levels up to ten times higher than levels found in the general population (Mannino et al., 1995; Romieu et al., 1999). Workers in the petroleum industry and those with solvent exposure can have blood ethylbenzene levels that are several hundred times higher than those in the general population (Angerer and Wulf, 1985; Kawai et al., 1992).
Finding a measurable amount of ethylbenzene in the blood does not imply that the level of ethylbenzene causes an adverse health effect. Biomonitoring studies of ethylbenzene in blood can provide physicians and public health officials with reference values so that they can determine whether people have been exposed to higher levels of ethylbenzene than are found in the general population. Biomonitoring data can also help scientists plan and conduct research on exposure and health effects.
Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological profile for ethylbenzene, November 2010 [online]. Available at URL: http://www.atsdr.cdc.gov/toxprofiles/tp.asp?id=383&tid=66. 8/3/12
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