Biomonitoring Summaries are intended to provide a brief general overview about the chemical or chemical group, including usage, environmental pathways, sources of exposure, toxicology, health effects, and human exposure information.Source: Centers for Disease Control and Prevention
CAS No. 71-43-2
Benzene is a volatile chemical that is produced commercially from coal and petroleum sources. It is among the most abundantly produced chemicals in the U.S. and is used extensively as an industrial solvent, in the synthesis of numerous chemicals, and as an additive in unleaded gasoline (ATSDR, 2007).
Human exposure occurs primarily by inhaling benzene in ambient air (Hattemer-Frey et al., 1990; Wallace, 1996). Sources of benzene in the air may result from either natural (e.g., forest fires) or industrial sources. Among industrial sources, automobile emissions and vapor around gasoline filling stations contribute to benzene in air (ATSDR, 2007). Tobacco smoke contributes to benzene in indoor air (Duarte-Davidson, et al., 2001), and tobacco smoke is estimated to account for about half of the total estimated exposure to benzene (ATSDR, 2007). Indoor sources for benzene, which include the offgassing of building materials, account for a significant portion of a non-smoker's benzene exposure (Wallace, 1996; Wallace et al., 1987). The consumption of food, drinking water, and beverages are considered negligible sources of exposure unless benzene contamination has occurred, such as from leaking underground fuel storage tanks (ATSDR, 2007; Wallace, 1996). In recent years, less than five percent of domestic wells used for drinking water in the U.S. have been found to contain detectable amounts of benzene (Rowe et al., 2007). Workplace exposure to benzene may result from production, use, or transportation of petroleum products.
Benzene is well absorbed after inhalational, oral, or dermal exposure. In the blood, benzene is distributed rapidly throughout the body, especially into the brain and fatty tissues, and can cross the placenta. Benzene is metabolized in the liver, and some metabolites may be distributed to the bone marrow, where additional metabolism may result in toxic effects on hematopoietic cells (ATSDR, 2007; Ross, 2000). The primary benzene metabolites are phenol, catechol, hydroquinone, 1,2,4-benzenetriol, and to a lesser extent, trans, trans-muconic acid, which are eliminated in urine as glucuronide and sulfate conjugates (Ross, 2000). Urinary S-phenylmercapturic and t,t-muconic acids are used for monitoring workplace exposure. A very small amount of unchanged benzene is eliminated in the breath.
Accidental and intentional exposures to high concentrations of benzene vapor can lead rapidly to euphoria, central nervous system depression, cardiac arrhythmias, followed by unconsciousness and death (ATSDR, 2007). Workers have developed skin irritation following repeated dermal exposure and mucous membrane irritation following repeated vapor inhalation (ATSDR, 2007). Epidemiologic studies of workers in industries involving benzene have found that benzene exposure can cause bone marrow suppression and increases the risk of various leukemias (Savitz and Andrews, 1997). Supportive evidence for benzene carcinogenicity comes from animal studies and from in vitro studies demonstrating the clastogenic properties of benzene on blood forming cells (NTP, 1986; Ross, 2000). The background exposure levels for the general population have been estimated to be much lower than the estimated lowest effect level for benzene at which leukemia risk is increased (Duarte-Davidson, et al., 2001).
Workplace standards and guidelines for benzene have been established by OSHA and ACGIH, respectively. The U.S. EPA has established environmental and drinking water standards for benzene, and the FDA has established a bottled water standard. Benzene is classified as a known human carcinogen by IARC and by NTP. Information about external exposure (ie., environmental levels) and health effects is available from ATSDR at: http://www.atsdr.cdc.gov/toxprofiles/.
Levels of blood benzene reflect recent exposure. The median level of blood benzene observed in the NHANES 2003–2004 subsample appear slightly lower than the median level in a nonrepresentative subsample of adults in NHANES III (1988–1994) (Ashley et al., 1994), as well for other previous studies of the U.S. general population (Bonanno et al., 2001; Buckley et al., 1997; Sexton et al., 2005 and 2006; Lin et al., 2008), and studies from other countries (Brugnone et al., 1994; Navasumrit et al., 2005).
Smoking, residing, or working in urban areas and exposure to gasoline and petroleum products can result in blood benzene levels that are higher than those in the nonsmoking general population (Ashley et al., 1995; Carrer et al., 2000; Backer et al., 1997). The amount and duration of cigarette smoking increases the likelihood of higher blood benzene levels (Bonanno et al., 2001; Churchill et al., 2001; Lin et al., 2008). Workers exposed to gasoline fumes, such as garage mechanics, drivers, and street vendors, and workers exposed to solvent fumes have been found to have blood benzene levels as much as tenfold higher than levels in the general population (Brugnone, et al., 1994 and 1999; Moolenaar et al., 1997; Perbellini et al., 2002; Romieu et al., 1999).
Finding a measurable amount of benzene in blood does not mean that the level of benzene causes an adverse health effect. Biomonitoring studies of blood benzene can provide physicians and public health officials with reference values so that they can determine whether or not people have been exposed to higher levels of benzene than levels found in the general population. Biomonitoring data can also help scientists plan and conduct research on exposure and health effects.
Benzene belongs to a class of chemicals called volatile organic compounds, so called because they evaporate in the air. Benzene is made from coal and petroleum sources and is present in gasoline. As one of the most commonly-made chemicals in the United States, benzene is often used to make many other chemicals. Benzene is also present in cigarette smoke.
How People Are Exposed to Benzene
People are exposed to benzene by breathing it in the air. Benzene gets into the air from forest fires, car emissions, gasoline vapors, and tobacco smoke. People who work with petroleum products, including gasoline, are exposed to benzene by touching or breathing in the chemical.
Benzene also can be absorbed into the body by eating food or drinking water or other beverages contaminated with benzene. These exposures are less common than breathing in the chemical.
How Benzene Affects People's Health
Breathing in unusually high doses of benzene can cause difficulty in thinking, changes in heart function, unconsciousness, or death. In smaller amounts over longer periods of time, benzene can also decrease the formation of blood cells. Benzene is considered to be a cancer-causing chemical.
Levels of Benzene in the U.S. Population
In the Fourth National Report on Human Exposure to Environmental Chemicals (Fourth Report), CDC scientists measured benzene in the blood of 1,345 participants aged twenty years and older who took part in the National Health and Nutrition Examination Survey (NHANES) during 2003–2004. The prior survey period of 2001–2002 is also included in the Fourth Report. By measuring benzene in blood, scientists can estimate the amount of benzene that has entered people's bodies.
- CDC researchers found benzene present in the blood of the majority of participants.
- Prior research has shown that people who smoke have more benzene in their blood.
Finding a measurable amount of benzene in the blood does not mean that levels of benzene cause an adverse health effect. Biomonitoring studies on levels of benzene provide physicians and public health officials with reference values so that they can determine whether people have been exposed to higher levels of benzene than are found in the general population. Biomonitoring data can also help health scientists plan and conduct research on exposure and health effects.
For More Information
- Agency for Toxic Substances and Disease Registry
Toxicological profile for benzene update
- Environmental Protection Agency
Consumer fact sheet on Benzene
What are the effects of Benzene exposure from the living within the heavy industry called; 'oil and gas?' Does anyone truly know? Why not? Would it make sense for communities in Colorado to start their own biomonitoring? All citizens must get this test done and keep the information as a baseline when future development occurs, you'll have a greater chance demonstrating the causal link of affects to your health from oil and gas development and fugitive emissions.
I think that in Weld County, Colorado, the results from biomonitoring would be shocking. I will personally get the blood, urine summary done and publish the results when it is complete. I've lived far too long in Weld County and its time for me to go! I believe the oil and gas industry should not operate with federal and state exemptions that harm the environment or humans. Somehow, the 'cost factor' was sadly overlooked. We are all victims of the industry's greed.