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Ethylbenzene

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Introduction

Ethylbenzene is a colorless liquid that smells like gasoline. It evaporates at room temperature and burns easily. Ethylbenzene occurs naturally in coal tar and petroleum. It is also found in many man-made products, including paints, inks, and insecticides. Gasoline contains about 2 percent (by weight) ethylbenzene. It is most commonly found as a vapor in the air. This is because ethylbenzene moves easily into the air from water and soil. Once in the air, other chemicals help break down ethylbenzene into chemicals found in smog. This breakdown happens in about 3 days with the aid of sunlight. In surface water such as rivers and harbors, ethylbenzene breaks down by reacting with other compounds naturally present in the water. In soil, the major way ethylbenzene is broken down is by soil bacteria. It can also move very quickly into groundwater, since it does not readily bind to soil. Near hazardous waste sites, the levels of ethylbenzene in the air, water, and soil could be much higher than in other areas.

Exposure Pathways

There are a variety of ways you may be exposed to this chemical. If you live in a highly populated area or near many factories or heavily traveled highways, you may be exposed to ethylbenzene in the air. Releases of ethylbenzene into these areas occur from burning oil, gas, and coal and from discharges of ethylbenzene from some types of factories. The median level of ethylbenzene in city air is about 0.62 parts of ethylbenzene per billion parts (ppb) of air. The median level in suburban air is about 0.62 ppb. In contrast, the median level of ethylbenzene measured in air in country locations is about 0.01 ppb. Indoor air has a higher median concentration of ethylbenzene (about 1 ppb) than outdoor air. This is because ethylbenzene builds up after you use household products such as cleaning products or paints.

Ethylbenzene was found in only 1 out of 10 of the United States rivers and streams tested in 1982 and 1983. The average level measured was 5.0 ppb. Ethylbenzene gets into water from factory releases, boat fuel, and poor disposal of waste. Background levels in soils have not been reported. Ethylbenzene may get into the soil by gasoline or other fuel spills and poor disposal of industrial and household wastes.

Some people are exposed to ethylbenzene in the workplace. Gas and oil workers may come into contact with ethylbenzene either through the skin or by breathing ethylbenzene vapors. Varnish workers, spray painters and persons involved in gluing operations may also be exposed to high levels of ethylbenzene. Exposure may also occur in factories that use ethylbenzene to produce other chemicals. Families of these workers may be exposed to ethylbenzene through contact with contaminated clothing.

You may be exposed to ethylbenzene if you live near hazardous waste sites containing ethylbenzene or areas where ethylbenzene spills have occurred. Higher than background levels of ethylbenzene were detected in groundwater near a landfill and near an area where a fuel spill had occurred. No specific information on human exposure to ethylbenzene near hazardous waste sites is available.

You may also be exposed to ethylbenzene from the use of many consumer products. Gasoline is a common source of ethylbenzene exposure. Other sources of ethylbenzene exposure come from the use of this chemical as a solvent in pesticides, carpet glues, varnishes and paints, and from the use of tobacco products. Ethylbenzene does not generally build up in food. However, some vegetables may contain very small amounts of it.

Metabolism

When you breathe air containing ethylbenzene vapor, it enters your body rapidly and almost completely through your lungs. Ethylbenzene in food or water can also rapidly and almost completely enter your body through the digestive tract. It may enter through your skin when you come into contact with liquids containing ethylbenzene. Ethylbenzene vapors do not enter through your skin to any large degree. People living in urban areas or in areas near hazardous waste sites may be exposed by breathing air or by drinking water contaminated with ethylbenzene.

Once in your body, ethylbenzene is broken down into other chemicals. Most of it leaves in the urine within 2 days. Small amounts can also leave through the lungs and in feces. Liquid ethylbenzene also enters through your skin and is broken down. Ethylbenzene in high levels is broken down slower in your body than low levels of ethylbenzene. Similarly, ethylbenzene mixed with other solvents is also broken down more slowly than ethylbenzene alone. This slower breakdown may increase the time it takes for ethylbenzene to leave your body.

Health Effects

At certain levels, exposure to ethylbenzene can harm your health. People exposed to low levels of ethylbenzene in the air for short periods of time have complained of eye and throat irritation. Persons exposed to higher levels have shown signs of more severe effects such as decreased movement and dizziness. No studies have reported death in humans following exposure to ethylbenzene. However, evidence from animals suggests that it can cause death at very high concentrations. Whether or not long-term exposure to ethylbenzene affects human health is not known because little information is available. Short-term exposure of laboratory animals to high concentrations of ethylbenzene in air may cause liver and kidney damage, nervous system changes, and blood changes. The link between these health effects and exposure to ethylbenzene is not clear because of conflicting results and weaknesses in many of the studies.

Also, there is no clear evidence that the ability to get pregnant is affected by breathing air, drinking water containing ethylbenzene, or coming into direct contact with ethylbenzene through the skin. Birth defects have occurred in newborn animals whose mothers were exposed by breathing air contaminated with ethylbenzene. The seriousness of these effects seems to increase with higher exposure levels. One long-term study in animals suggests that ethylbenzene may cause tumors. However, this study had many weaknesses and no conclusions could be drawn about possible cancer effects in humans. EPA has determined that ethylbenzene is not classifiable as to human carcinogenicity.

Low levels of ethylbenzene in the air may cause harmful health effects. More serious effects to your health may occur at higher levels. You can smell ethylbenzene in the air at concentrations as low as 2 parts of ethylbenzene per million parts of air by volume (ppm).

There are no reliable data on the effects in humans after eating, drinking, or breathing ethylbenzene or following direct exposure to the skin. For this reason, levels of exposure that may affect your health are estimated from animal studies. Only two reports described the results of eye or skin exposure to ethylbenzene. In these studies, liquid ethylbenzene caused eye damage and skin irritation in rabbits. More animal studies are available that describe the effects of breathing air or drinking water containing ethylbenzene.

Information excerpted from:

Toxicological Profile for Ethylbenzene December 1990 Update

Agency for Toxic Substances and Disease Registry
U.S. Dept. of Health and Human Services

Structural diagram:

National Institutes of Health