Ethylbenzene
CASRN 100-41-4 (endorsed 2013)
Guideline
Based on aesthetic considerations (taste and odour), the concentration of ethylbenzene in drinking water should not exceed 0.003 mg/L.
Based on health considerations the concentration of ethylbenzene in drinking water should not exceed 0.3 mg/L.
General description
Ethylbenzene is a clear colourless liquid, which occurs naturally as a component of crude oil. It constitutes approximately 1-2% of unleaded gasoline by volume.
Ethylbenzene is produced commercially by the alkylation of benzene with ethylene, and by fractionation of petroleum. It is a major component of commercial xylene and is used commercially in paints, insecticides, blends of petrol, and in the production of styrene. It can also be found as a constituent of asphalt and naphtha.
Ethylbenzene has a taste and odour threshold of 0.003 mg/L.
Typical values in Australian drinking water
Ethylbenzene has only rarely been identified in Australian drinking waters. Natural concentrations in most water sources are usually very low. Ethylbenzene can occur naturally in groundwater as a result of proximity to, or contact with, coal seams, petroleum and gas deposits, and shales. It may be mobilised by extraction activities (Lesage et al., 1997; Leusch and Bartkow, 2011; Volk et al, 2011). However, contamination can occur, usually via exposure to petrochemicals in surface waters or groundwater. Known sources of groundwater contamination include leakage from sub-surface fuel storage tanks (do Rego & Netto, 2007). Emissions of fuel components from boating use is a known source of contamination of multiple-use lakes and reservoirs (Schmidt et al., 2004). Ethylbenzene is generally not detected in groundwater (<0.001 mg/L), but concentrations in contaminated groundwater in the USA were as high as 2 mg/L (IPCS, 1996). Ethylbenzene has been reported at up to 0.000 2 mg/L in municipal drinking water in Croatia (Karaconji et al., 2006), up to 0.011 mg/L in municipal drinking water in Taiwan (Kuo et al., 1997) and is occasionally detected in drinking waters in the USA (Williams et al., 2004) at concentrations up to 0.002 mg/L (ATSDR, 2010). Concentrations in Canadian drinking water ranged from <0.001 - 0.01 mg/L (IPCS, 1996).
Treatment of drinking water
Volatile organic chemicals such as ethylbenzene are most commonly treated in drinking water by aeration stripping and/or adsorption to granular activated carbon (GAC). A conventional biologically active sand filter has been shown to be highly effective for the removal of ethylbenzene from contaminated water, under suitable conditions (Arvin et al., 2004). Effective bioremediation of highly contaminated groundwaters has also been demonstrated (Sedran et al., 2004; Zein et al., 2006).
Measurement
A purge and trap gas chromatographic procedure can be used for the analysis of ethylbenzene (APHA, AWWA & WEF, 2012). An inert gas is bubbled through the sample and ethylbenzene is trapped on an adsorbent. The adsorbent is then heated and ethylbenzene analysed using gas chromatography with mass spectrometric (GC-MS) detection (Method 6200 B) or photoionisation (PI) detection (Method 6200 C) (APHA, AWWA & WEF, 2012). The method detection limit is 32 ng/L for GC-MS and 28 ng/L for GC-PI (APHA, AWWA & WEF, 2012).
Health considerations
Ethylbenzene is readily absorbed from the human gastrointestinal tract. It can be stored in fat and is metabolised to mandelic and phenylglyoxalic acids and excreted in the urine. It can cross the placenta.
No data are available on the health effects in humans after oral exposure, and inhalation data are limited to short term studies.
A 6 month gavage study using rats reported enlargement of the liver and kidney at high doses (400 mg/kg body weight per day) (Wolf et al., 1956). Mellert et al. (2007) also reported liver and kidney related impacts in addition to hepatocyte hypertrophy from 4 and 13 week gavage studies using rats at doses above 75 mg/kg bw/day. No longer-term studies are available.
Studies on the mutagenic activity of ethylbenzene to bacteria, insects and mammalian cells have reported negative results.
Ethylbenzene is classified as Group 2B (possibly carcinogenic to humans) by the International Agency for Research on Cancer (IARC, 2000).
Derivation of guideline
The USEPA (2009) has set a drinking water guideline of 0.7 mg/L for ethylbenzene, while the WHO (2011) proposes a guideline of 0.3 mg/L.
The health-based guideline value for ethylbenzene in drinking water was determined as follows:
Where:
75 mg/kg body weight per day is the no effect level based on a 4 and 13 week gavage study using rats (Mellert et al. 2007).
70 kg is the average weight of an adult
0.1 is the proportion of total daily intake attributable to the consumption of water
2 L/day is the average amount of water consumed by an adult
1000 is the safety factor in using the results of an animal study as a basis for human exposure (10 for interspecies variations, 10 for intraspecies variations and 10 for the limited data and short duration of the study)
This health-based value exceeds the taste and odour threshold of 0.003 mg/L for ethylbenzene in water.
The WHO drinking water guideline value is the same (0.3 mg/L) but is based on a no effect level of 136 mg/kg bw/d for hepatoxicity and nephrotoxicity in a limited 6-month study with rats (WHO, 2011).
References
American Public Health Association (APHA), American Water Works Association (AWWA) and Water Environment Federation (WEF) (2012). Standard Methods for the Examination of Water and Wastewater, 22nd Edition. Eds. Rice EW, Baird RB, Eaton AD and Clesceri LS.
Arvin, E., Engelsen, P. and Sebber, U. (2004) Biodegradation of gasoline compounds (BTEX) in a water works sand filter. Water Science & Technology: Water Supply, 4(5-6), 29-33.
ATSDR (2010). Toxicological profile for ethylbenzene.US Department of Health and Human Services, Agency for Toxic Substances and Disease Registry, USA.
do Rego, E. C. P. and Netto, A. D. P. (2007) PAHs and BTEX in groundwater of gasoline stations from Rio de Janeiro City, Brazil. B. Environ. Contam. Tox., 79(6), 660-664.
IARC (International Agency for Research on Cancer) (2000) IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, volume 77: Some industrial chemicals. Lyon, France.
IPCS (1996). Environmental Health Criteria 186: Ethylbenzene. International Programme on Chemical Safety, World Health Organization, Geneva, Switzerland.
Karaconji, B., Skender, L. and Karacic, V. (2006) Benzene, toluene, ethylbenzene, and isomeric xylenes in various water samples in Croatia. B. Environ. Contam. Tox., 76(3), 458-462.
Kuo, H. W., Chiang, T. F., Lo, L. I., Lai, J. S., Chan, C. C. and Wang, J. D. (1997) VOC concentration in Taiwan’s household drinking water. Sci. Total Environ., 208(1-2), 41-47.
Lesage, S., Hao, X., and Kent, S. (1997) Distinguishing Natural Hydrocarbons from Anthropogenic Contamination in Ground Water. Groundwater, 35(1), 149-160
Mellert W., Deckhardt K., Kaufmann W and van Ranvenzwaay B. (2007) Ethylbenzene: 4- and 13-week rat oral toxicity. Arch Toxicology 81: 361-370
Schmidt, T. C., Haderlein, S. B., Pfister, R. and Forster, R. (2004) Occurrence and fate modeling of MTBE and BTEX compounds in a Swiss Lake used as drinking water supply. Water Res., 38(6), 1520-1529.
Sedran, M. A., Pruden, A., Wilson, G. J., Suidan, M. T. and Venosa, A. D. (2004) Biodegradation of methyl tert-butyl ether and BTEX at varying hydraulic retention times. Water Environ. Res., 76(1), 47-55.
USEPA (2009) National Primary Drinking Water Regulations. United States Environmental Protection Agency, Washington, DC, USA.
Volk, H., Pinetown, C., Johnston,W. (2011) A desktop study of the occurrence of total petroleum hydrocarbon (TPH) and partially water-soluble organic compounds in Permian coals and associated coal seam groundwater. CSIRO Petroleum and Geothermal Research Portfolio Report EP-13-09-11-11 2011 (Bentley, WA, Australia).
WHO (2011) Guidelines for Drinking Water Quality, 4th Edition. World Health Organisation, Geneva, Switzerland.
Wolf, M. A., Rowe, V. K., McCollister, D. D., Hollingsworth, R. L. and Oyen, F. (1956) Toxicology studies of certain alkylated benzenes and benzene: experiments on laboratory animals. AMA Archives of Industrial Health, 14, 387–398.
Zein, M. M., Suidan, M. T. and Venosa, A. D. (2006) Bioremediation of groundwater contaminated with gasoline hydrocarbons and oxygenates using a membrane-based reactor. Environ. Sci. Technol., 40(6), 1997-2003.
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