Chemical carcinogens types

Tumours induced by chemical carcinogens/irradiation Each tumour usually displays distinct antigen specificity Virally induced tumours Various tumour types display identical tumour-... 

Models for determining the dose-response relationship vary based upon the type of toxicological hazard. In the dose-response for chemical carcinogens, it is frequently assumed that no threshold level of exposure (an exposure below which no effects would occur) exists, and, therefore, any level of exposure leads to some finite level of risk. As a practical matter, cancer risks of below one excess cancer per million members of the population exposed (1 x 10 ), when calculated using conservative (risk exaggerating) methods, are considered to represent a reasonable certainty of no harm (Winter and Francis, 1997). 

Price, P.J. Mishra, N.K. (1980) The use of Fischer rat embryo cells as a screen for chemical carcinogens and the role of the nontransforming type C RNA tumor viruses in the assay. Adv. mod. environ. Toxicol.. 1. 213-239... 

Another line of evidence that free radicals may be involved in chemical carcinogenesis is that antioxidants often act as anti-cancer compounds. Many types of chemical carcinogens, in a variety of organs and in many animal species, are protected against... 

Subsequently, Ras was found to be mutated in chemical carcinogen-induced rodent tumors and in many types of human cancer. Ras is a member of a larger group of normal cellular genes, termed proto-oncogenes, that can be altered to... 

Personnel protective equipment may be used in certain circumstances where exposure to airborne particulates contaminated with chemical carcinogens could occur. In those situations, personnel should be equipped with a complete clothing change, as well as respiratory protection selected on the basis of work performed, type of chemical used, and containment equipment. The respiratory protection may be a face mask, respirator [selected from those approved by the National Institute for Occupational Safety and Health (NIOSH)] (4, 5), or emergency breathing air system. In the latter case, a head hood or a complete protective suit may be used with a breathing air supply system. Figure 2. 

Personal Hygiene Practices. All personnel should wear disposable or other type gloves resistant to research materials (3) and wash their hands immediately after removing gloves following the completion of any procedure in which chemical carcinogens are used. A hand washing facility should be made available within the laboratory. 

Work Surfaces. All horizontal work surfaces (bench tops, containment cabinets or fume hoods) should be protected with impervious material to prevent contamination of the work surfaces with chemical carcinogens. One of the systems that has proved useful is to use the dry, absorbent polyethylene-backed paper (Benchkote, VWR Scientific Co., Cat. No. 52855 , Continuous Sheet Type, Scientific Products Co., Cat. No. P1180). Following contamination, or upon completion of an experiment, or at the end of the day, this protective cover can be rolled up, packaged for safe removal, and disposed of in an appropriate manner. 

Model VG201, Spectroderm International, Inc., Fairfax, Virginia 22030. If volatile chemical carcinogens are used, a separate vacuum pump or vacuum system should be used in conjunction with an appropriate laboratory-type containment cabinet. 

Decontamination/Collection. Research operations should be analyzed to determine the types of waste, quantities of carcinogenic material, and handling procedures to be employed. All chemical carcinogens, including those contained in animal carcasses, should be deactivated, degraded if feasible, or packaged... 

In general, four types of cabinets are used for work with research quantities of chemical carcinogens. These are the conventional fume hood a Class I biological safety cabinet a Class II (Type B) biological safety cabinet and a Class III closed glove box system (8). 

The facility must be designed to control access. Signs should designate restricted areas. Clothing requirements for entry should be identified. There should be directional air control with adequate ventilation rates. Primary containment equipment such as chemical fume hoods, a Class I or Class II (Type B) biological safety cabinet, or a glove box system should be available for use with known or suspect chemical carcinogens or other toxic substances. 

In these studies, a stereoselective metabolism has been used as a tool to phenotype individuals for (iso)enzymes or enzyme systems that, in principle, can activate xenobiotics into chemical carcinogens. Obviously, information on stereoselectivity and structure biotransformation relationships may be worthwhile to predict this type of tcodcity-related bio-transformation. 

Vitamin A deficiency in animals leads to a greater frequency of various types of cancer. Most of these animal studies involved the induction of cancer using chemical carcinogens, that is, by feeding, injection, or application to the skin. 

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