health as it helps in predicting cancer rates and provides a basis for appropriate
recommendations for cancer prevention.
10.1 Introduction
Cancer is caused by changes in genes that alter the way our cells perform their
normal functions. Some of these genetic changes occur naturally when DNA is
replicated during the process of cell division while others are the result of environmental exposures that damage DNA. Studies have shown that among the factors
responsible for cancer, environmental factors play an important role particularly
tobacco and alcohol (Brennan and Boffetta 2004). The relationship between cancer
development and use of tobacco and alcohol was analyzed by two systematic
reviews published by The World Cancer Research Fund in 2007 (World Cancer
Research Fund 2007) and the International Agency for Research on Cancer in 2012
(International Agency for Research on Cancer 2012). The reviews concluded that
long-term alcohol and tobacco consumption increases risk of cancer of the lips, oral
cavity, pharynx, larynx, lung, stomach, colorectum, breast, pancreas, and liver.
Similarly, studies have also been conducted that show that there is a relationship
between cancer onset and alcohol consumption and tobacco smoking. The higher the
amount of alcohol and tobacco consumed, the greater is the risk of cancer in the long
term. However, inter-individual variations in susceptibility to cancer have also been
observed. Individuals having the same amount and duration of usage of tobacco and
alcohol may have differences in susceptibility to cancer which might be explained by
gene–environment interactions. The genetic make-up of an individual decides the
outcome of an exposure to a carcinogen (Fig. 10.1). Study of gene–environment
interaction helps to improve accuracy and precision in the assessment of both genetic
and environmental influences. Following sections discuss the risk factors for cancer,
namely alcohol and tobacco, genetic variations in key enzymes and gene–environment interactions.
10.2 Environmental Risk Factors and Cancer Risk
10.2.1 Tobacco and Cancer Risk
The use of tobacco is a leading cause of cancer and also death from cancer. People
who consume tobacco products or who are regularly around environmental tobacco
smoke (also called second hand smoke) have an increased risk of cancer because
tobacco products and second hand smoke have components that damage DNA.
Processed tobacco leaves possess more than 3000 chemicals (Roberts 1988) which
include leaf constituents as well as constituents derived from multiple sources.
Unburned tobacco products contain carcinogenic nitrosamines, polycyclic aromatic
hydrocarbons (PAHs), radioactive elements, and cadmium. Several forms of tobacco
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recommendations for cancer prevention.
10.1 Introduction
Cancer is caused by changes in genes that alter the way our cells perform their
normal functions. Some of these genetic changes occur naturally when DNA is
replicated during the process of cell division while others are the result of environmental exposures that damage DNA. Studies have shown that among the factors
responsible for cancer, environmental factors play an important role particularly
tobacco and alcohol (Brennan and Boffetta 2004). The relationship between cancer
development and use of tobacco and alcohol was analyzed by two systematic
reviews published by The World Cancer Research Fund in 2007 (World Cancer
Research Fund 2007) and the International Agency for Research on Cancer in 2012
(International Agency for Research on Cancer 2012). The reviews concluded that
long-term alcohol and tobacco consumption increases risk of cancer of the lips, oral
cavity, pharynx, larynx, lung, stomach, colorectum, breast, pancreas, and liver.
Similarly, studies have also been conducted that show that there is a relationship
between cancer onset and alcohol consumption and tobacco smoking. The higher the
amount of alcohol and tobacco consumed, the greater is the risk of cancer in the long
term. However, inter-individual variations in susceptibility to cancer have also been
observed. Individuals having the same amount and duration of usage of tobacco and
alcohol may have differences in susceptibility to cancer which might be explained by
gene–environment interactions. The genetic make-up of an individual decides the
outcome of an exposure to a carcinogen (Fig. 10.1). Study of gene–environment
interaction helps to improve accuracy and precision in the assessment of both genetic
and environmental influences. Following sections discuss the risk factors for cancer,
namely alcohol and tobacco, genetic variations in key enzymes and gene–environment interactions.
10.2 Environmental Risk Factors and Cancer Risk
10.2.1 Tobacco and Cancer Risk
The use of tobacco is a leading cause of cancer and also death from cancer. People
who consume tobacco products or who are regularly around environmental tobacco
smoke (also called second hand smoke) have an increased risk of cancer because
tobacco products and second hand smoke have components that damage DNA.
Processed tobacco leaves possess more than 3000 chemicals (Roberts 1988) which
include leaf constituents as well as constituents derived from multiple sources.
Unburned tobacco products contain carcinogenic nitrosamines, polycyclic aromatic
hydrocarbons (PAHs), radioactive elements, and cadmium. Several forms of tobacco
212
M. Ruwali and R. Shukla