Benzene

what is a hydrocarbon derivative

What is benzene?

Benzene is the name of an aromatic hydrocarbon, C6 H6 .

In liquid form, benzene is clear, colorless and flammable. At room temperature, liquid benzene evaporates easily into the air, and can dissolve in water. In the environment, benzene may be present in air, water, and soil. It is also a naturally occurring product of decomposition in some foods.

Where does benzene come from?

Benzene comes mainly from petroleum. It has been used in, or used to manufacture, a wide variety of chemical products, including DDT (dichloro-diphenyl- trichloroethane), detergents, insecticides and motor fuels. Used as a substitute for lead, benzene now makes up 1 to 2 percent of every gallon of gasoline and it is released as a by-product of fuel combustion.

Benzene is also produced in the burning of tobacco, and is one of the nearly 4,000 chemicals found in tobacco smoke. The once widespread use of benzene as a solvent in paints, adhesives, and paint removers has decreased in recent years.

What are the health effects of benzene?

Half of the benzene a person inhales is then exhaled. The rest is temporarily stored in the body’s bone marrow and fat. The liver and bone marrow break benzene down into metabolites (the products of physical or chemical processes in the body). Some of these metabolites, such as hydroquinone, are more toxic than benzene. The metabolites are then eliminated from the body after about two days.

  • Benzene is a carcinogen. While many chemicals are suspected to be cancer-causing, benzene is one of the few substances that have been identified by the U.S. Environmental Protection Agency as a “known human carcinogen.” The International Agency for Cancer Research has also determined that benzene is carcinogenic to humans.
  • Occupational studies of workers exposed to benzene have shown that long-term exposure to high levels has caused acute myeloid leukemia. In laboratory studies with rats and mice, benzene has been shown to cause leukemia and other types of cancer.
  • Benzene can cause neurological damage and can harm the immune system. Long-term exposure to benzene fumes can cause nerve damage. Short-term exposure to high levels of benzene, and to other related aromatic hydrocarbons such as toluene and xylene, can cause dizziness, nausea, headaches and unconsciousness. Excessive exposure to benzene can harm the immune system.
  • Sensitive Populations—As with most chemicals, benzene poses a potentially greater hazard to young children and pregnant women. Studies indicate that alcohol consumption increases the toxicity of benzene.

How might I be exposed to benzene in Vermont?

  • Outdoor Air - Vermont has lower levels of benzene in outdoor air than is found in many of the more industrial or densely populated areas of the United States. Most of the outdoor levels of benzene in Vermont result from automobile traffic. The more traffic in a given town, the higher the benzene levels in the air. The air around fuel pumps at gasoline stations may have higher levels of benzene, although vapor recovery systems recently installed by many gas stations

    have greatly reduced this source of exposure.

Benzene vapors may be elevated in the area around bulk fuel terminals and fuel delivery tank trucks. Another source of exposure is older outboard motors on boats, which tend to release unburned gasoline into lakes and streams. The benzene in these emissions is highly volatile and readily evaporates into the air.
  • Indoor Air - Exchange of air between indoors and out means that indoor air levels of benzene can be as high as the outdoor levels in any given area. There are circumstances under which indoor air levels may be substantially higher. This is possible, for example, in buildings with an attached garage containing cans of fuel products. Any unvented combustion that takes place in a home - using a kerosene heater or a gas-cooking stove, for example - will release additional benzene into the air.

    Placing benzene-saturated clothes in a washing machine without first thoroughly airing them out will also release benzene into the indoor air. If clothes become saturated with gasoline or other fuel oils containing benzene, they should be hung outside to evaporate the benzene before machine-washing.

    The largest contributor of benzene to indoor air is cigarette smoke. In a national survey of household air quality, homes of non-smokers had average benzene levels of 2.2 ppb and homes of smokers had average levels of 3.3 ppb. The benzene levels in bars that permit smoking have been measured at between 8 and 13 ppb. People who smoke absorb 10 times as much benzene in a day as do non-smokers.

    For information on other indoor air exposure problems, see our fact sheets on Volatile Organic Compounds and Air Quality in Homes .

  • Skin - If fuels are spilled on the skin, some of the benzene can penetrate the skin and be absorbed into the body.
  • Water - Wells may become contaminated with benzene as a result of gasoline spills. Benzene in water remains very volatile, and it will quickly find its way into the air of the affected homes. The highest exposure will be during a shower; the hotter the water, the more the benzene will evaporate into the air. For more information, see our fact sheet on Volatile Organic Compounds in Drinking Water .
  • Food - Benzene is found in small amounts in fruits, vegetables, meats and dairy products. (It has not been found in cow or breast milk). However, exposure to benzene as a result of eating is minimal.
  • There are no medical tests to determine long-term exposure to low levels of benzene.

    There are no generally useful tests for determining the extent of an individual’s benzene exposure. The benzene disappears quickly in the body, and the very high levels of resulting metabolites will not be detected unless the initial exposure was implausibly high.

    Currently there are no tests that are useful in determining long-term, low-level exposure to benzene. People who work in specific occupations that cause them to be exposed to benzene can be monitored by urine testing.

    Source: healthvermont.gov

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