Carcinogens 3,4,-benzene pyrene

Outside of carbon monoxide for which the toxicity is already well-known, five types of organic chemical compounds capable of being emitted by vehicles will be the focus of our particular attention these are benzene, 1-3 butadiene, formaldehyde, acetaldehyde and polynuclear aromatic hydrocarbons, PNA, taken as a whole. Among the latter, two, like benzo [a] pyrene, are viewed as carcinogens. Benzene is considered here not as a motor fuel component emitted by evaporation, but because of its presence in exhaust gas (see Figure 5.25). 

Polycyclic aromatic hydrocarbons, which are built of fused benzene rings, include naphthalene, anthracene, and phenanthrene. Some, such as benzo[a]pyrene, are carcinogens. Graphite, a common allotrope of carbon, consists of layers of planar,... 

Many xenobiotic chemicals are not by themselves carcinogenic, but require metabolism to the ultracarcinogens that form DNA adducts. Examples of these include benzene and benzo (a) pyrene, which are metabolized to their hydroquinones, the carcinogenic agents)18 2128 3()l... 

One TPH compound (benzene) has been shown to cause cancer (leukemia) in people. The International Agency for Research on Cancer (IARC) has determined that benzene is carcinogenic to humans (Group 1 classification). Some other TPH compounds or petroleum products, such as benzo(a)pyrene and gasoline, are considered to be probably and possibly carcinogenic to humans (IARC Groups 2A and 2B, respectively) based on cancer studies in people and animals. Most of the other TPH compounds and products are considered not classifiable (Group 3) by IARC. See Chapter 6 for more information on how TPH can affect your body. 

Carcinogenic Effects. Specific petroleum hydrocarbon indicator compounds that have EPA cancer potency factors are assessed these are benzene and benzo(a)pyrene. EPA relative potency factors can be used for benz(a)anthracene, indeno(l,2,3-cd)pyrene, dibenz(a,h)anthracene, chrysene, benzo(b)fluoranthene, and benzo(k)fluoranthene. 

Carcinogenic Effects. Specific petroleum hydrocarbon indicator compounds that have EPA cancer potency factors are assessed (i.e., benzene and benzo(a)pyrene). 

The potential of basic fractions of coal tar creosote to accelerate tumor induction by known carcinogens was evaluated by Sail and Shear (1940). A 1% solution of the basic fraction of creosote oil in benzene was dermally applied to female strain A mice alone or in conjunction with 0.05 or 0.02% benzo[a]pyrene. The basic fraction alone did not induce skin tumors, but when applied in conjunction with either concentration of benzo[a]pyrene, skin tumors appeared more rapidly than when benzo[a]pyrene alone was applied. Maximum tumor induction was seen between 28 and 42 weeks 19 of 20 mice developed tumors. 

Polycyclic aromatic hydrocarbons (PAHs) represent a class of compounds that contain two or more fused benzene rings. They are environmental pollutants and the most ubiquitous, benzo[a]pyrene (B[a]P), has been upgraded by the International Agency for Research on Cancer to a Group 1 or known human carcinogen [1]. PAHs are products of fossil fuel combustion they are a component of fine particulate matter (size 2.5pm) and as a consequence contaminate the air we breathe, the soil and water supply, and enter the food chain [2, 3]. They are also introduced artificially into smoked, cured, and barbecued food [4, 5], Finally, they are present as a complex mixture in tobacco smoke and second-hand smoke, and are suspect causative agents in human lung cancer [6]. 

Benzene dioxide and benzene trioxide are also known [10]. Arene oxides are crucial intermediates in the carcinogenic action of benzo[ z]pyrene and other polycondensed arenes [11]. Oxiranes are found relatively rarely in nature. An example of an oxirane in a natural product is, however, the juvenile hormone of the sphinx moth. 

Lu P-Y, Metcalf RL (1975) Environmental fate and biodegradability of benzene derivatives as studied in a model aquatic ecosystem. Environ Health Perspect 10 269-284 Lu P-Y, Metcalf RL, Plummer N, Mandel D (1977) The environmental fate of three carcinogens benzo(a)pyrene, benzidene, and vinyl chloride evaluated in laboratory model ecosystems. Arch Environ Contam Toxicol 6 129-142... 

Although many aromatic compounds are essential to life, others are hazardous. Many are quite toxic, and several benzenoid compounds, including benzene itself, are carcinogenic. Two other examples are benzo[rz]pyrene and 7-methylbenz[rt]anthracene ... 

HC f lithium hydride, methyUsocyanate, toluene diisocyanate, 2,4,6-trinitrotoluene (TNT), tri-o-cresylphosphate, vinyl chloride... 

PAHs comprise a large group of chemical carcinogens found in the workplace. This group of hydrophobic, non-polar compounds is formed by a pyrolitic process, such as the combustion of organic compounds (lARC 1983). PAHs are made up of two or more benzene rings and are exemplified by the chemical benzo[ a] pyrene (lARC 1983). Workers are exposed to PAHs mainly from inhalation, but also from skin contact (Bofetta 1997)- The highest exposure to PAHs (where PAHs are... 

Benzene itself is quite toxic to humans and can cause severe liver damage toluene, although not harmless. Is much less toxic. How can such different behavior of two very similar compounds be possible To eliminate benzene from the body, the aromatic ring must be oxidized, but intermediates in this oxidation are damaging. However, the methyl side chain of toluene can be oxidized to give benzoic acid, which can be excreted. None of the intermediates in this process causes health problems. Conversely, nitro-substituted PAHs, especially of benzo[a]pyrene, are often about 1 0 times more carcinogenic than their unsubstituted analogues, and studies are currently underway to understand this effect. 

Many polycyclic aromatic hydrocarbons are formed in the combustion of organic compounds and are dispersed into soils and sediments. Some, like benzene itself and pyrene, are carcinogens that are present in cigarette smoke. 

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