Benzene is an aromatic hydrocarbon with the molecular formula C6H6. It is sometimes abbreviated Ph–H. Benzene is both an anthropogenically produced and naturally occurring chemical. It is a component of products derived from coal and petroleum and is found in gasoline and other fuels. Benzene is used in the manufacture of plastics, detergents, pesticides, and other chemicals. It is also a carcinogenic emission produced in the coking process of coal mining.
Benzene and coal
Benzene and coal mining
Benzene in coal mining poses a potential health threat to coal miners and those who live in close proximity to coal mining facilities. Benzene is an emission produced in the coking process of coal mining. Exposure to long term low levels of benzene in the work environment or acute short term exposure can lead to a number of health problems ranging from nausea, insomnia, headache and dizziness to convulsions, coma, cancer, chromosomal aberrations, anemia and even death. There are several types of leukemia that have been linked to benzene exposure, which hinders or disables an individual's bone marrow from properly producing red blood cells, white blood cells and/or platelet cells in the blood.
The standards set by the Occupational Safety and Health Administration (OSHA) require that levels of benzene in coal mining and other workplace environments cannot exceed one part per million for an eight hour day and five parts per million in a fifteen minute period. Employers are required to monitor benzene in coal mining and other industries when levels reach 0.5 parts per million. Exposure to benzene in coal mining at the beginning of the 1900s was as high as one thousand parts per million.
Benzene found near coal seam gas fracking site
In October 2010, farmers near a coal seam gas "fracking" site in Queensland announced that they will have their water supplies tested for toxic benzene and other chemicals after Origin Energy found contaminated water near drilling sites. The discovery of BTEX - a mixture of benzene, toluene, ethylbenzene and xylene - around eight coal seam gas wells near Miles, west of Brisbane, marks the first time a resources company has admitted to contaminating water at a fracking site. Origin detected the chemicals in mid-October and told the Queensland government, which is legislating to ban the use of BTEX chemicals during coal seam gas drilling. Origin has shut down all 17 of its drilling rigs across a 40-kilometre-wide area while an investigation is carried out.
Fracking, or hydraulic fracturing, involves injecting water, sand and chemicals underground to fracture rock formations and force gas to the surface. The controversial process has fuelled protests from landholders in Australia and the United States, where government tests have detected harmful levels of hydrocarbons, including BTEX, in drinking water wells in areas where fracking is used. Origin refused to disclose the mixture of chemicals used in the fracking fluid that it was using on the site. The US company Halliburton supplied the fluids. Origin's manager of oil and gas operations, Paul Zealand, said BTEX was not being used as a fracking fluid, and that the contamination may have come from diesel fuel or lubricants used on machinery at the gas drilling sites. An engineering consultancy, URS, and the government will investigate.
In 2006, a computer investigation by Environmental Working Group (EWG) uncovered results from a Food and Drug Administration (FDA) testing program that contradicted safety assurances about benzene contamination in soft drinks made by a top agency official on March 21, 2006. FDA data showed that 79 percent of diet soda samples tested over a six-year period from 1995 through 2001 were contaminated with benzene at levels above the federal limit for benzene in tap water.
"The FDA test results, buried deep within an obscure FDA food testing program called the Total Diet Study, were posted on EWG's Web site, www.ewg.org, just days after a top FDA official assured the public that there was no threat from the presence of the toxic chemical in soft drinks." 
In drinking water, the Environmental Protection Agency (EPA) has set the maximum contamination level at five parts per billion. The EPA has also set the level of benzene permissible in outdoor air levels at five parts per billion.
Research has shown benzene to be a carcinogen (cancer-causing). With exposures from less than five years to more than 30 years, individuals have developed, and died from, leukemia. Long-term exposure may affect bone marrow and blood production. Short-term exposure to high levels of benzene can cause drowsiness, dizziness, unconsciousness, and death.
- "Benzene" OSHA, accessed October 2010.
- "Benzene in Coal Mining" OL, accessed October 2010.
- Ben Cubby, "Origin stops coal seam gas drilling after chemicals found in water" Sydney Morning Herald, October 21, 2010.
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- "Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use," National Academy of Sciences, 2009