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Chemical Carcinogenesis

Dr Prashant Kumbhaj MD,DM(Medical Oncology), MRCP SCE (Medical Oncology) ECMO,PDCR.

What is a Chemical Carcinogenesis ?


1.Any discrete chemical compound which has been shown to cause cancer in human or animal studies.
2. Hundreds of individual compounds have been shown to induce cancers. Many thousands of additional compounds are ''suspect'' carcinogens.
3. Many are commonly used in laboratory operations, shops and art studios.

Which classes of chemicals tend to be Chemical Carcinogenesis ?


1. Epoxides: Ethylene oxide ,Propylene oxide
2. Organohalogen comp.:Vinyl chloride Carbon tetrachloride Chloroform Hexachlorobenzene Trichloroethylene
3. Hydrazines: Hydrazine (and salts) 1,2-Dimethylhydrazine
4. N-Nitroso compounds:N-Nitrosodimethylamine
5. Aromatic Amines:Benzidine Aniline o-Anisidine o-Toluidine
6. Aromatic hydrocarbons:Benzene Benz[a]anthracene Benzo[a]pyrene

Classes of Chemical Carcinogenesis (cont.)


1. Misc. organic compounds:Formaldehyde Acetaldehyde 1,4-Dioxane Ethyl carbamate 2-Nitropropane Styrene Thiourea Thioacetamide
2. Misc. inorganic comp.Arsenic and compounds Chromium and comp. Thorium dioxide Beryllium and compounds Cadmium and compounds Lead and compounds Nickel and compounds Selenium sulfide

How do Chemical Carcinogenesis enter the body ?


1. Skin absorption. Many solvents and other chemicals go directly through the skin.
2. Ingestion. Swallowing of a carcinogen.
3. Inhalation. Breathing gases, fumes and vapors is the most common form of exposure.

Mechanism


1. Chemical carcinogens undergo metabolic activation by cytochrome P450 or other metabolic pathway and react with DNA or alter epigenetic mechanism .
2.DNA is considered the ultimate target for most carcinogens to cause mutations or gross chromosomal changes.
3.Formation of DNA Adducts occurs by binding of chemicals to DNA
4. Carcinogen -DNA Adducts leads to base mutation or gross chromosomal changes ,so that it can cause base substitution ,deletion ,insertion duroing DNA replication .


Carcinogenic Chemicals in our daily life.

1.Charred Foods

 

charred foods

2.Refined white Flours
 

                            Refined white Flours
                          3.Microwave Popcorn

               The Microwave Popcorns contain Perfluorooctanoic acid (PFOA) and which is a likely carcinogen.
                The inhalation of vapour of artificial butter present in it which contains dangerous chemicals and
                can cause kidney and lung cancers.Perfluorooctanoic acid (PFOA)- Use in food wrappers,candy



                          4.Fruit Ripening agents(Carcinogens)
     1.  With the development of fruit trade the fruits are sent to distant places, requiring several days in
     ordinary or refrigerated transportation and only firm and mature fruits are least damaged during
     marketing.
     2.  The fruits are ripened at the destination markets before retailing and hence artificial ripening has
   become essential.
     3.The most commonly used chemical for artificial ripening is Calcium Carbide (CaC2) and is popularly known as "Masala",
     though banned under PFA Rules, 1955 and
    also under Food Safety and Standards (Prohibition and Restrictions on Sales) Regulations.
    4. Calcium Carbide is colourless when pure, but greyish-white to black in colour otherwise, with garlic like odour.
     When it reacts with water, it produces acetylene gas (popularly referred to as carbide gas) which
    is an analogue to ethylene and quickens the ripening process. It is said to have the same
     effect as ethylene the natural ripening hormone.
    CaC2 + 2H2O -> C2H2 + Ca (OH)2

     5.However, acetylene is not nearly as effective for ripening as is ethylene and acetylene is not a natural hormone as ethylene.
     Calcium Carbide contains traces of Arsenic and Phosphorous hydride.
     6. A strong reactive chemical, Calcium Carbide has carcinogenic properties and is used in gas welding.
     Being cheap and easily available in the local markets, CaC2 is indiscriminately being used in
     preference to other recommended practices of inducing ripening in fruits
                                                                                                    PESTICIDES CANCER AND FOOD ADULTRATION