Question
What are polynuclear hydrocarbons? Discuss the toxicity of polynuclear hydrocarbons.
Solution
Polynuclear hydrocarbons are the compounds which contain two or more benzene rings. They may be either fused or isolated.
(i) Fused polynuclear hydrocarbons: These are condensed aromatic hydrocarbons which contain more than one ring and have two carbons shared by two or more aromatic rings.
(ii) Isolated polynuclear hydrocarbons. In isolated polynuclear hydrocarbons, one or more benzene rings are linked to each other through one or more carbon atoms.
Toxicity of polynuclear hydrocarbons:
There are certain polynuclear hydrocarbons which are cancer producing (i.e. carcinogenic nature). Actually, these are the products of incomplete combustion of organic material such as coal, petroleum, tobacco etc. and become a major cause of human cancer. The following polynuclear hydrocarbons are cancer producing:
It is believed that when these polynuclear hydrocarbons enter the body of a human being, they are first converted into their oxides called epoxides and then into dihydroxy epoxides. The dihydroxy epoxides thus produced react with purine bases (such as guanine) present in DNA and RNA of the human cell, thereby causes mutation and ultimately leads to cancer. Also all over the world, steps are being taken to check the release of such toxic polynuclear hydrocarbons in the atmosphere.
(i) Fused polynuclear hydrocarbons: These are condensed aromatic hydrocarbons which contain more than one ring and have two carbons shared by two or more aromatic rings.
(ii) Isolated polynuclear hydrocarbons. In isolated polynuclear hydrocarbons, one or more benzene rings are linked to each other through one or more carbon atoms.
Toxicity of polynuclear hydrocarbons:
There are certain polynuclear hydrocarbons which are cancer producing (i.e. carcinogenic nature). Actually, these are the products of incomplete combustion of organic material such as coal, petroleum, tobacco etc. and become a major cause of human cancer. The following polynuclear hydrocarbons are cancer producing:
It is believed that when these polynuclear hydrocarbons enter the body of a human being, they are first converted into their oxides called epoxides and then into dihydroxy epoxides. The dihydroxy epoxides thus produced react with purine bases (such as guanine) present in DNA and RNA of the human cell, thereby causes mutation and ultimately leads to cancer. Also all over the world, steps are being taken to check the release of such toxic polynuclear hydrocarbons in the atmosphere.
