7 Carcinogenic Nature of Emerging Contaminants: Havoc for Present …
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7.12 Carcinogenic Mechanism Triggered by Some
Emerging Contaminants
7.12.1 Arsenic
The mechanism of carcinogenesis induced by arsenic involves process of biotransformation. Inside the body, the heavy metal Arsenic initiates a number of methylation,
oxidation and reduction reaction (Ebert et al. 2011). Arsenical species undergoes
reduction from pentavalent state to trivalent state during glutathione-dependent reaction (Németi et al. 2010). After that oxidative methylation occurs where dimethylarsenate, methylarsonate and monomethylarsonous acid are produced (Drobna et al.
2009; Rossman 2003; Rossman and Klein 2011). Arsenic triggers a fast depolarization of membrane of mitochondria, collectively causing deleation and depletion of
Deoxyribonucleic acid (DNA) resulting in cancer among human beings (Partridge
et al. 2007; Ruiz-Ramos et al. 2009).
7.12.2 Asbestos
If the asbestos fibres which are inhaled are longer, i.e. around five micrometre, then
it is not removed by the process of phagocytosis effectively. As a result of this,
a series of molecular reactions occur, leading to inflammation, carcinogenesis and
fibrosis (Xu et al. 2007; Choe et al. 1998). Moreover, the asbestos fibres which are
completely phagocytized can cause interference in mitosis, thereby causing chromosomal missegregation (Ault et al. 1995). During the incomplete procedure of
phagocytosis of asbestos fibres, reactive nitrogen and oxygen species are released
which causes damage to the DNA (Hei et al. 2006). The reactive oxygen species
is hydrogen peroxide (Xu et al. 2007). Asbestos fibres which are rich in iron like
amosite and crocidolite generate higher amount of reactive oxygen species (Srivastava et al. 2010). Alike arsenic, asbestos also causes damage to mitochondrial DNA
and results in reactive oxygen species derived from mitochondria leading to trigger
base oxidation, breakage of single strands (Panduri et al. 2004; Aljandali et al. 2001).
Hence, carcinogenis induced by asbestos is expected to happen by causing chronic
inflammation via oxidative stress which effectively damages DNA.
7.12.3 Radon
Though, inert chemically, radon is capable of decaying in electrically charged active
progenies and on attachment with aerosols, it can be inhaled and finally reaches
epithelial cells of lungs. On the final deposition, radon undergoes decay, releasing
alpha particles and free radicals which ultimately harm DNA (Samet et al. 2009).
169
7.12 Carcinogenic Mechanism Triggered by Some
Emerging Contaminants
7.12.1 Arsenic
The mechanism of carcinogenesis induced by arsenic involves process of biotransformation. Inside the body, the heavy metal Arsenic initiates a number of methylation,
oxidation and reduction reaction (Ebert et al. 2011). Arsenical species undergoes
reduction from pentavalent state to trivalent state during glutathione-dependent reaction (Németi et al. 2010). After that oxidative methylation occurs where dimethylarsenate, methylarsonate and monomethylarsonous acid are produced (Drobna et al.
2009; Rossman 2003; Rossman and Klein 2011). Arsenic triggers a fast depolarization of membrane of mitochondria, collectively causing deleation and depletion of
Deoxyribonucleic acid (DNA) resulting in cancer among human beings (Partridge
et al. 2007; Ruiz-Ramos et al. 2009).
7.12.2 Asbestos
If the asbestos fibres which are inhaled are longer, i.e. around five micrometre, then
it is not removed by the process of phagocytosis effectively. As a result of this,
a series of molecular reactions occur, leading to inflammation, carcinogenesis and
fibrosis (Xu et al. 2007; Choe et al. 1998). Moreover, the asbestos fibres which are
completely phagocytized can cause interference in mitosis, thereby causing chromosomal missegregation (Ault et al. 1995). During the incomplete procedure of
phagocytosis of asbestos fibres, reactive nitrogen and oxygen species are released
which causes damage to the DNA (Hei et al. 2006). The reactive oxygen species
is hydrogen peroxide (Xu et al. 2007). Asbestos fibres which are rich in iron like
amosite and crocidolite generate higher amount of reactive oxygen species (Srivastava et al. 2010). Alike arsenic, asbestos also causes damage to mitochondrial DNA
and results in reactive oxygen species derived from mitochondria leading to trigger
base oxidation, breakage of single strands (Panduri et al. 2004; Aljandali et al. 2001).
Hence, carcinogenis induced by asbestos is expected to happen by causing chronic
inflammation via oxidative stress which effectively damages DNA.
7.12.3 Radon
Though, inert chemically, radon is capable of decaying in electrically charged active
progenies and on attachment with aerosols, it can be inhaled and finally reaches
epithelial cells of lungs. On the final deposition, radon undergoes decay, releasing
alpha particles and free radicals which ultimately harm DNA (Samet et al. 2009).