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Benzene is a clear, colourless, highly flammable and volatile liquid aromatic hydrocarbon with a gasoline-like odour. It is present in crude oil and is produced as a by-product when we refine crude oils. Benzene is a multipurpose compound, serving its use in a variety of different fields. It primarily acts as a raw material or ‘building blocks’ to produce other industrial chemicals such as phenols and toluene.1 Benzene and its compounds such as cyclohexane are also frequently used as organic solvents in pharmaceutical industries. Ultimately, a wide range of compounds formed from benzene become frequently used consumer goods in almost every industry ranging from household plastics to medicinal drugs to materials such as nylon used in the clothing industry (Jenny C. Heumann, 2019).1 Most of the final products are formed as a result of a sequence of reactions with various compounds, however, the origins can be traced back to benzene, highlighting its importance in modern society.1
Benzene was first discovered by the English scientist, Michael Faraday in the year 1825. Interest in benzene rapidly rose as scientist’s struggled to explain its unique and mind-boggling properties (F. A. Carey, 2019).2 However, it wasn’t until 1866, that the German chemist August Kekule von Stradonitz finally theorised and proved the shape of the unique structure of benzene, paving the way for mass adoption of benzene throughout the chemical industry. He proposed benzene to be composed of a cyclic arrangement of six carbon atoms with alternating single and double bonds. The image to the right of this paragraph represents this structure.3 This theory was later modified to one in which the double bonds of the compound rapidly shifted, effectively producing two equivalent structures for the same compound (F. A. Carey, 2019).2
Benzene can be found in consumer goods like gasoline, adhesives, paint, tobacco smoke and water that have been contaminated. Due to its highly volatile nature, benzene poisoning usually occurs due to inhalation (WHO, 2010).5 The short term effects of benzene exposure depend upon the type of poisoning. If it is inhaled, symptoms like drowsiness, dizziness, rapid heart rate, confusion, weakness and unconsciousness may be experienced. On the other hand if it is ingested it could cause discomfort in the abdomen alongside vomiting, convulsions and pain (Mickey P. Landry, Frank J. Swarr, 2018).4 High levels of exposure through inhalation can also significantly damage the lungs resulting in fluid accumulation and bleeding. In addition, if highly concentrated benzene vapour or liquid spills on skin then it can cause second degree burns. Furthermore, women may experience irregular menstrual cycles and have their fertility levels affected (Mickey P. Landry, Frank J. Swarr, 2018).4
The biggest issue with benzene, however, correlates to its properties as a carcinogenic (Cancer-causing) substance. According to the International Agency for Research on Cancer (IARC), Benzene lies alongside cigarettes and Asbestos as one of the most highly carcinogenic substances present in our everyday lives. Its link to leukaemia and other forms of cancer is undeniable based on evidence from experiments and tests conducted on lab animals (Mickey P. Landry, Frank J. Swarr).4 Upon entering the human body, benzene interferes with several metabolic reactions and biological pathways taking place in the liver to bone marrow. This leads to the production of two molecules, t, t-muconaldehyde and 1, 2, 4-benzenetriol which have been associated with higher levels of chromosomal changes and gene mutation commonly observed in acute myeloid leukaemia (Cliona M. McHale, Luoping Zhang and Martyn T. Smith, 2012).6
Being a carcinogenic substance and having other adverse negative consequences to health and the environment, handling benzene must be done with utmost care. The U.S. Occupational Safety and Health Administration (OSHA) regulate benzene exposure on an industrial scale and have enforced rules to decrease benzene exposure for the past 40 years. An example of this is their 1 part per million benzene regulation for the average workday in an industrial environment. Companies are required to uphold OSHA regulations and enable workers to handle benzene in a safe and controlled environment (Jenny C. Heumann, 2007).7 Additionally, the increased use of catalytic converters in modern vehicles has also helped reduce benzene emissions as an unburnt hydrocarbon.
Smoking and passive smoking are also large contributors to benzene exposure. In the United States, the cumulative effect of smoking accounts for nearly half of all exposure to benzene from any source especially in enclosed settings where the benzene concentration is left to accumulate (B. A. Pallinger, 2005).8 However, as a result of stricter policies on public smoking over the last decade, this cause of benzene exposure is predicted to be less impactful in the coming years.
While chemists and researchers are hard at work around the world searching for a safer alternative to benzene, momentarily we have no choice but to bear with the risk that accompanies the use of benzene in the industry. However, due to the implementation of stricter safety regulations and many other advances in technology, the risk of working with benzene is now far lower than it ever was and it will only become safer as newer and equally practical organic molecules are discovered.
Written by Abhinav Senthil, Kritin Mukundan, Manav Vedant Kasi and Adrian Nomi
Bibliography
1 C. Heumann, Jenny (2019, June 15). What Is Benzene?: Chemical Safety Facts. Retrieved from https://www.chemicalsafetyfacts.org/benzene/
2 Carey, F. A. (2019, July 26). Benzene. Retrieved from https://www.britannica.com/science/benzene
3 Structure of Benzene. Retrieved from http://chemistry2.csudh.edu/rpendarvis/BenzStr.html
4 (2018, May 31). Signs of Benzene Exposure. Retrieved from https://www.landryswarr.com/signs-of-benzene-exposure/
5 W. H. O. (2010). Preventing disease through healthy environments. Retrieved from https://www.who.int/ipcs/features/benzene.pdf
6 Current understanding of the mechanism of benzene-induced leukaemia in humans, By Cliona M.McHale, Luoping Zhang, and Martyn T. Smith, 2012, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3271273/
7 Heumann, J. (2007, August). Toxic Substances Portal - Benzene. Retrieved from https://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=38&tid=14
8 Pallinger, B. A. (2005, December 14). Reducing Occupational Exposure to Benzene in Workers and Their Offspring. Retrieved from https://www.apha.org/policies-and-advocacy/public-health-policy-statements/policy-database/2014/07/09/14/47/reducing-occupational-exposure-to-benzene-in-workers-and-their-offspring
9 Bünger, J. (2002, January). Emissions of benzene with and without catalytic converters. Retrieved from https://www.researchgate.net/figure/Emissions-of-benzene-with-and-without-catalytic-converter-for-different-blends-Farymann_fig4_226905543
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