Māris kļaviņŠ, azamat azizov, JĀnis zaļoksnis environment, pollution, development: the case of uzbekistan

Figure 6.11. 
Effects of 
various causal factors on 
the mortality rate from 
malignant tumours

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6. Action of toxic substances in the environment – basic concepts of ecotoxicology 
 115
The development of malignant tumours is to a large extent 
determined not only by genetic factors and the predisposition of an 
organism but by the action of substances on particular elements of 
the human genome. Arguably, if the action of substances and factors 
that promote the development of cancer were prevented, the number 
of cancer occurrences would decrease, even though it is not easy to 
prove the effects of hazardous factors and substances because there 
is often a considerable time span between the action of a substance 
and tumour development.
The most common carcinogens are substances of anthropogenic 
origin,  but  also  natural  substances.  Aflatoxins  are  an  example  of 
such a natural substance; they originate from moulds and contribute 
to liver cancer development.
However, when the cells stimulated in this way are not subject 
to mutation, they do not transform into cancerous cells.
Food and substances used for intoxication (e.g., alcohol, tobacco, 
drugs) can be a source of carcinogens. Tobacco smoke contains 
many carcinogens. Alcohol and foods with a high fat and low fibre 
content may also increase the risk of developing malignant tumours. 
Mould growing on protein-rich products (e.g., rice, peanuts) may 
contain aflatoxin. Contact with carcinogenic substances and factors 
such as benzene, tar products and radiation may take place at the 
work environ ment. Furthermore, viruses can be quite an important 
factor contributing to the development of cancer – for example, the 
Epstein-Barr virus, which belongs to the Herpesviridae family.