Carcinogens benzene

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). 

The press centre on the Website of British Petroleum pic (BP) is a good source of information, at http //www.bpamoco.com/centres/press/index.asp. For example, the page http //www.bpevo.com/bpevo main/asp/evo glo 0003.asp lists the terms used by most petrol companies, and http //www.bp.com/location rep/uk/bus operating/ manu ops.asp cites the amounts of the known carcinogen, benzene, found naturally in petrol. 

Decomposition and aromatization of ethanol on Fe-ZSM-5 [68] or M02C/ZSM type catalysts [69, 70]. This reaction, however, produces mainly aromatics there are continuous more stringent regulations on the use of aromatics in fuels due to their carcinogenicity (benzene) and toxicity. 

As discussed in detail in Chapters 6 and 16, organic compounds play a key role in the formation of ozone, particles, and other species of interest. While some of the individual species are of concern from the point of view of health effects (e.g., the carcinogens benzene and 1,3-butadiene), for most VOC it is because of their... 

Very little is known about the influence of the use of other solvents on the yield, although it is expected that other aprotic solvents would be as efficient as benzene. Toluene and CH2CI2 are interesting alternatives to the use of carcinogenic benzene, which have been proved to be efficient in this oxidation. e It can be advisable to cool the reaction flask on an ice-water bath during the initial mixture of components on multigram scale oxidations when exotherms can be expected. As the DMSO freezes at 18°C, operations at low temperature must be done in the presence of a co-solvent, like benzene. f Normally, it takes between 1 h and 1 day. 

This fluorine-containing, oxidation-resistant alcohol is best oxidized by the Pfitzner-Moffatt reaction, using dichloroacetic acid as catalyst. Observe the use of toluene, instead of carcinogenic benzene, as solvent. A Swern oxidation was not reproducible, and caused substantial epimerization of the isobutyl side chain. Collins oxidation was successful, but ... 

Lawesson s reagent was used for the first preparation of carotenoid thiones [76] from canthaxanthin, rhodoxanthin and echinenone (carcinogenic benzene could very probably have been replaced as solvent by toluene, xylene or THF ). 

In contrast, the most common industrial halo-genated solvents such as methylene chloride, chloroform, perchloroethylene, and carbon tetrachloride have long been identified as suspected human carcinogens. Benzene and other aromatic hydrocarbons have also been associated with the causation or promotion of cancer in humans and animals. All of these substances are widely used because of their excellent solvent properties in a wide range of applications. Nevertheless, regulations have been issued in the United States, for example (under the Clean Air Act) to control many of these chemicals... 

Carcinogenic) Benzene, like most hydrocarbons is very easy to dry. No preliminary drying is required and several reagents will reduce the water content to < Ippm. Alumina, calcium hydride, and 4A sieves (all 3% w/v for 6h) are the most convenient drying agents and the benzene is then distilled and stored over 4A sievesi( ). Alternatively benzene may be dried over calcium hydride in a continuous still. Toluene may be dried in the same way. 

Toluene is widely used in industry as a replacement for the carcinogenic benzene, but toluene also exhibits considerable toxicity. In vivo, toluene is oxidized the main metabolite in man is benzoic acid, which is then conjugated with glycine and excreted in urine as hippuric... 

Using the equation provided in the problem statement, the action level for the carcinogen benzene for an 80-kg person with a life expectancy of 70 years and an exposure duration of 15 years is... 

An important industrial application of CD is the alkylation of benzene with ethylene or propylene to produce ethylbenzene or cumene, respectively, using acidic ion-exchange resins such as Amberlyst or zeolites operating at 130-5065 kPa and 80-500°C. Cumene is a chemical intermediate for the production of phenol, acetone, and alpha-methyl styrene, which are used to produce resins and solvents. Ethylbenzene is an intermediate for styrene, an important monomer for polymers. Alkylation of benzene could also be used to reduce the carcinogenic benzene content of gasoline. 

A maximum of 1% of the carcinogen benzene (a 50%i reduction) and a maximum of 25 /o for aromatic hydrocarbons (compared with 40% previously). 

EPDH (ethylene-propylene-diene) Use of halogen-based flame retardants in special products as well as possible exposure to neurotoxic n-hexane and carcinogenic benzene at production and processing. PS ... 

Many surfactants are made from petroleum with hazardous reagents. Sulfur trioxide was used with the carcinogen benzene to make the alkylbenzenesulfonates described earlier. The carcinogen ethylene oxide is used to make many nonionic surfactants from phenols and long-chain alcohols. A common surfactant, sodium dodecyl sulfate, is made from an alcohol derived from coconut oil by reduction followed by treatment with sulfur trioxide. Long-chain tertiary amines derived from natural fats and oils are quat-ernized with methyl chloride. Perhaps this can be done with... 

The carcinogen benzene (derived from petroleum) is the starting point for many important industrial chemicals. The syntheses often involve stringent conditions and may pro-... 

The health effects of exposure to liquid benzene or benzene fumes depends on the amount of benzene taken into the body. The most common symptoms of benzene exposure include irritation of the mucous membranes, convulsions, depression, and restlessness. At greater doses, a person may experience respiratory failure, followed by death. Even at low concentrations, benzene can cause longterm effects for people who are regularly in contact with the compound. The most important of these effects are carcinogenic. Benzene is known to cause damage to bone marrow, resulting in a form of cancer of the blood known as leukemia. 

Avoid HCB and BHC because of suspected carcinogenicity. (Benzene hexachloride is more correctly termed hexachlorocyclohexane.)... 

Most of the alkane, alkene, and alkyne hydrocarbon compounds are considered to be flammable as their major hazard, and the toxicity is considered as moderate to low. The vapors are more likely to be asphyxiant than toxic. TLVs range from 50 ppm for hexane to 300 ppm for octane. Decane is listed as having a narcotic effect. Many of these hydrocarbons are found in mixtures, and it will be necessary to look at the Material Safety Data Sheets (MSDS) to obtain toxicity information on particular mixtures. Benzene, toluene, and xylene are aromatic hydrocarbons. They are considered highly toxic and human carcinogens. Benzene has a TLV of 0.1 ppm in air, according to the NIOSH Guide 1997 Addition, and an STEL of 1 ppm. The OSHA STEL is 5 ppm and a PEL of 1 ppm. Toluene is toxic by ingestion, inhalation, and skin absorption. The TLV for toluene is 100 ppm in air. Xylenes are toxic by... 

While the number of particles is important as they are related to health effects, so too is the size, shape, material properties and chemical composition. Chemicals absorbed or adsorbed into the particles may also have different toxicological effects. In addition to carbon particles and polycyclic aromatic hydrocarbons (PAHs), indoor air can accumulate environmental tobacco smoke as well as chemicals such as biocides, formaldehyde, and volatile organic compounds (VOCs) classified by the International Agency for Research on Cancer (lARC) as carcinogenic (benzene, 1,3-butadiene) (lARC 1995). Since children are the most affected by chronic household exposure, they may be at higher risk of cancer. It was demonstrated a relative increase in leukaemia and lymphoma caused by indoor VOCs as well as by the... 

Four billion pounds of adipic acid are produced each year using petroleum-based feedstocks, carcinogenic benzene as starting material, and extreme reaction conditions. Nitrous oxide, which plays a role in ozone layer depletion, is emitted as a byproduct. As an alternative to the currently employed synthetic methcdology, a two-step synthesis of adipic acid from D-glucose has been developed which eliminates each of these problems. A microbial catalyst was created which possesses a novel biosynthetic pathway that synthesizes cis, cis-muconic acid from D-glucose. This pathway does not occur in nature but has been created in a strain of Escherichia colL Cis, cw-muconic acid is exported to the culture supernatant, where it is hydrogenated under mild conditions to yield adipic acid. 

In addition to direct toxic effects of substances, whether to hnmans or more generally in the environment, other environmental effects may also need to be taken into account. Natural gas, for example, is toxic only to the extent that it carries traces of substances such as the carcinogen benzene. However, if released nnderground, it can lead to the displacement of oxygen, with adverse effects on roots and soil microorganisms. Accompanying changes in soil conditions such as pH and redox potentials can also lead to the mobilization of heavy metals. 

With regard to carcinogenicity, benzene has long been recognized as carcinogen in man. It is the reason why its use is strictly limited and not recommended (ICH class I/speci-fications 2 ppm). Carbon tetrachloride and 1,2-dichloroethane have been demonstrated to be carcinogenic in animals and potentially carcinogenic in man. 

To be carcinogenic, benzene must first be metabolized in the liver, mainly via cytochrome P4502E1. The major product is phenol (19), which is either conjugated—primarily to phenyl sulfate in humans—or further hydroxylated by P450 2E1 to hydroquinone. Other major metabolites include catechol (34) and trans-trans-mucomc acid (189 1,6-hexadienedioic acid). The latter is presumed to be formed from the ring opening of benzene epoxide (190 benzene oxepin), or perhaps benzene dihydrodiol (191 3,5-cyclohexene-l,2-diol). ... 

Between 2005 and 2009, the hydraulic fracturing companies used 95 products containing 13 different carcinogens. These included naphthalene (a possible human carcinogen), benzene (a known human carcinogen), and acrylamide... 

On the other hand, for the same amoimt of the carcinogen benzene, which has a vapor pressure of 95 mmHg, the lifetime drops to a value of... 

Consider a shallow dump, 10 m in diameter and biuied at a depth x = 5 m. In one case, it contains, dispersed in it, 100 mol of a toxic substance with a low vapor pressure of 10 mmHg = 1.3 Pa. In the second case, the substance is the carcinogen benzene with a vapor pressiue of 95 mmHg = 1.25 x 1(F Pa. Setting aside removal by water seepage and bacterial action, what would be the lifetime of these toxins ... 

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