Once benzene enters the digestive system, it is metabolized, and certain metabolites can be measured in the urine.
Another process, called toluene disproportionation, may be used when the goal is to produce aromatics called xylenes (there are three types of xylenes) along with benzene.
In 1987, OSHA estimated that about 237,000 workers in the United States were potentially exposed to benzene, and it is not known if this number has substantially changed since then.
EPA requires that spills or accidental releases into the environment of 10 pounds (4.5 kg) or more of benzene should be reported to the agency.
Animal studies have shown low birth weights, delayed bone formation, and bone marrow damage when pregnant animals breathed benzene.
During the reaction, some toluene molecules lose their methyl groups to produce benzene molecules (as above), while other toluene molecules gain methyl groups to produce xylene molecules (each of which has two methyl groups).
In 1845, Charles Mansfield, working under August Wilhelm von Hofmann, isolated benzene from coal tar.
Industries that involve the use of benzene include rubber manufacturers, oil refineries, chemical plants, shoe manufacturers, and gasoline-related industries.
Workers in various industries that make or use benzene may be at risk of exposure to high levels of this carcinogenic chemical.
The industrial production of benzene relies on three major chemical processes: catalytic reforming, toluene hydrodealkylation, and steam cracking.
Water and soil contamination are important pathways for the transmission of benzene.
Benzene can participate in several types of reactions, some of which are given below.
The latter may be blended with other hydrocarbons as a gasoline additive, or distilled to separate it into its components, including benzene.
European petrol (gasoline) specifications now contain the same one percent limit on benzene content.
In 2005, after an explosion at the China National Petroleum Corporation (CNPC) factory in Jilin, China, benzene leaked into the Songhua River.
Up until World War II, benzene was produced mainly as a byproduct of coke production in the steel industry.
The cyclic nature of benzene was finally confirmed by the crystallographer Kathleen Lonsdale.
Using the technique known as X-ray diffraction, researchers discovered that all the carbon-carbon (C-C) bonds in benzene have the same length (140 picometers (pm)).
Benzene (also known as benzol or -annulene) is a colorless, flammable, sweet-smelling liquid.
Benzene has been the subject of studies by many famous scientists, including Michael Faraday and Linus Pauling.
The linking of two benzene rings gives biphenyl (C6H5-C6H5).
Today, most benzene comes from the petrochemical industry, with only a small fraction being produced from coal.
Eating or drinking foods containing high levels of benzene can cause vomiting, stomach irritation, dizziness, sleepiness, convulsions, rapid heart rate, and death.
The U.S. Environmental Protection Agency (EPA) has set the maximum permissible level of benzene in drinking water at 0.005 milligrams per liter (0.005 mg/L).
Another test measures benzene in the blood; but because benzene disappears rapidly from the blood, measurements are accurate only for recent exposures.
Today, benzene is mainly used as an intermediate to make a variety of other chemicals.
In 1903, Lugwig Roselius popularized the use of benzene to decaffeinate coffee.
Trace amounts of benzene may result whenever carbon-rich materials undergo incomplete combustion.
Scientists who were familiar with the chemical formula of benzene (C6H6) were mystified about its molecular structure.
Benzene damages the bone marrow and can cause a decrease in the production of red blood cells, leading to anemia.
The U.S. Department of Health and Human Services (DHHS) classifies benzene as a human carcinogen.
The aromatic products are extracted from the reaction mixture with any of a number of solvents, such as diethylene glycol or sulfolane, and benzene is separated from the other aromatics by distillation.
Long-term exposure to high levels of benzene in the air can cause leukemia, a potentially fatal cancer of the blood-forming organs.
The major effect of benzene from chronic (long-term) exposure is on the blood.
Friedrich August Kekulй von Stradonitz is usually credited with being the first to deduce the ring structure of benzene, in 1865.
Consequently, before the 1950s, gasoline often contained several percent benzene.