MOLECULE

Benzene

Benzene is a colorless, highly flammable liquid with a characteristic sweet smell. It is partially responsible for the characteristic aroma around gasoline stations. Benzene is used primarily as a precursor to the manufacture of chemicals with more complex structure, such as ethylbenzene and cumene. Benzene has a high-octane number and as a result benzene along with various aromatic derivatives like toluene and xylene typically comprise up to 25% of gasoline. Exposure to gasoline or to plant combustion products is the most frequent reason for benzene to be detected in living organisms. Outdoor air frequently contains low levels of benzene from car service stations, wood smoke, tobacco smoke, the transfer of gasoline, exhaust from motor vehicles, and industrial emissions. Low levels of benzene appear to exist and to be produced naturally in all living organisms, ranging from bacteria to plants to humans. Benzene can be produced naturally through spontaneous reactions in cells, in biofluids and in fruits or juices. In particular, benzoic acid and ascorbic acid (Vitamin C) in the presence of iron or copper ions can interact to produce benzene (PMID: 26904662). Benzene has been found in a number of processed foods and plants, with the highest concentration being in safflowers. Benzene has also been detected, but not quantified in other plant foods, such as common beans, guava, and lovages. Benzene is a known degradation or combustion product arising from smoking, vaping or dabbing tobacco, cannabis or cannabis oils (PMID: 28983528). About 50% of an individual's exposure to benzene results from smoking tobacco (or other plant products) or from exposure to tobacco smoke (PMID: 9463546). Smoking 40 cigarettes per day leads to the intake of about 3 milligrams (mg) of benzene (PMID: 29266361). This amount is about 10 times the average daily intake of benzene by nonsmokers. Typically, benzene is produced by burning wood, tobacco or cannabis at temperatures above 200 oC. It primarily arises from the degradation of high-abundance terpenes including myrcene, limonene and linalool (PMID: 28983528). These terpenes, when heated, initially break down into isoprene which then recombines or oxidizes to produce a variety of volatile combustion/degradation products including: methacrolein; methyl vinyl ketone; hydroxyacetone; 3-methylfuran; 2-methylnapthalene; 1,3-butadiene; 1-methylcyclohexa-1,4-diene; and benzene (PMID: 28983528). Benzene is frequently elevated in the breath of tobacco and cannabis smokers. Benzene is a known human carcinogen and is classified by IARC (International Agency for Research on Cancer) as a class I (most serious) carcinogen. Benzene is also a notorious cause of bone marrow failure. Substantial quantities of epidemiologic, clinical, and laboratory data link benzene to aplastic anemia, acute leukemia, bone marrow abnormalities and cardiovascular disease (PMID: 20070208; PMID: 24932584). Human exposure to benzene is a global health problem. Benzene targets the liver, kidney, lung, heart and brain and can cause DNA strand breaks and chromosomal damage.