Carcinogens types

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 identification of Tris as a potential carcinogen dealt a resounding blow to the flame-retardant finishing industry. From 1977 to 1984, several principal supphers of flame-retardant chemicals either reduced the size of their operations or abandoned the market completely. However, Albright and Wilson Corp. (UK) continues to produce THPC—urea precondensate and market it worldwide, and Westex Corp. (Chicago) continues to apply precondensate—NH finish to millions of yards of goods for various end uses. American Cyanamid reentered the market with a precondensate-type flame retardant based on THPS. 

Nitrosamines. Findings that secondary amines, so common in mbber accelerators, can react with NO species to form the suspected human carcinogens, nitrosamines, have prompted active programs to develop alternative accelerators. Neither primary nor tertiary amines form stable nitrosamines and they are generally considered to be safe materials. The abiHty of each type of common mbber accelerator class to form nitrosamines has been summarized and depends on their 1°, 2°, or 3° nature (30). 

A further consensus developed within the scientific community regarding the relative carcinogenicity of the different types of asbestos fibers. There is strong evidence that the genotoxic and carcinogenic potentials of asbestos fibers are not identical in particular mesothelial cancer is mostiy, if not exclusively, associated with amphibole fibers (43). 

Ethylene dibromide is a suspected human carcinogen and worker exposure by all routes should be carefiiUy controUed to levels as low as reasonably achievable (67). Ethylene dibromide causes severe blistering of the skin if contact is prolonged. Eye contact with the Hquid will cause pain, irritation, and temporary impairment of vision. Recommended safety equipment includes safety goggles, a NIOSH approved canister-type gas mask for organic vapors, neoprene gloves, and neoprene overshoes. In case of contact with ethylene dibromide, contaminated clothing and shoes should be removed and eyes or skin washed with plenty of water for at least 15 minutes. Contaminated clothes should be washed before reuse and contaminated shoes should be discarded. 

Aldehyde-amines Aldol-naphthylamines Yes Not often used. Possibilities of carcinogenic hazard with some types. 

However, for some type of adverse effects, such as genotoxicity, carcinogenicity, and respiratory sensitization, it may not be possible from present knowledge to define this threshold of activity, so we may conclude that any level of exposure might carry some finite risk. In this case, OELs should be established at levels sufficiently low to avoid risks these are called pragmatic OELs. 

Another type of time-weighted average exposure limit is the decision level (DL), which is expressed as a fraction of the OEL. In general, it is based on judgment, and it is greater than a dose of 50% and usually corresponds to one-fourth of the dose. For special substances, such as carcinogens, it should... 

Because of the number of citations, only selected imidazoquinolines are described, and biological activity is mentioned only briefly. The largest increase in the number of citations was caused by the discovery of the antibacterial properties of nalidixic acid type drugs. Efforts to prepare the bioisosters, for example of oxolinic acid, intensified in the early 1970s, and the discovery of the carcinogenic properties of 2-aminoimidazoquinolines followed in the early 1980s. These azoloquinolines can be considered as benzene-separated deazapurines. 

As alkylating agent an alkyl halide, alkyl tosylate or dialkyl sulfate is used in most cases the latter type of reagent is often used in the preparation of methyl and ethyl ethers by employing dimethyl sulfate and diethyl sulfate respectively. Dimethyl sulfate is an excellent methylating agent, but is acutely toxic as well as carcinogenic." ... 

Elydrocarbons of many different types are present in exliaust gas. In the presence of nitrogen oxide and sunlight, they form oxidants that irritate the mucous membranes. Some hydrocarbons are considered to be carcinogenic. Incomplete combustion produces unburned hydrocarbons. 

Certain compounds of this type are potent carcinogens. One of the most dangerous is benzo[a]pyrene, which has been detected in cigarette smoke. It is believed to be a cause of lung cancer, to which smokers are susceptible. 

Some laboratory studies with rats and mice have linked trichloroethylene exposure to various types of cancers. Several of these studies, however, should be viewed cautiously, since the tumorigenic activity might be influenced by the presence of direct-acting compounds, namely the epoxides (e.g., epichlorohydrin) added as stabilizers in trichloroethylene. Epoxides are known to be very reactive, and some, such as epichlorohydrin, are potent carcinogens themselves. 

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