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

 6.3.5.  Carcinogenic effects of environmental pollutants 
and factors
A major adverse effects of environ mental pollutants is associated 
with their role in malignant tumour development. Malignant 
tumour is a generic term for more than 200 diseases characterised 
by uncontrolled cell division. Malignant tumours that develop in 
connective tissues are called sarcomas, whereas those that develop in 
epithelium tissue – cancers. Tumours develop not only in humans but 
also in animals and plants. Benign tumours grow slowly, moving the 
surrounding tissues. They are often encapsulated, do not form meta-
stases and do not recur. Usually the forms of tumours are classi fied 
according to the location of the tumour in the body or certain organs, 
for example, the circulatory system cancer, lung cancer, brain cancer. 
Different  forms  of  cancer  have  different  causes.  A  range  of  cancer 
risk  factors  have  been  definitely  proven,  for  instance,  smoking, 
radioactive radiation, unhealthy diet. Heredity is considered one of 
the  main  risk  factors.  There  are  families  that  have  a  significantly 
higher risk of developing cancer than others. For example, a woman’s 
risk of developing breast cancer increases from 1.5 to 3 times if her 
mother or sister had it. Sometimes breast cancer is associated with 
specific gene mutations, which are prevalent among certain ethnic 
groups or families. The possibility that women with such a gene 
mutation will develop breast cancer is significantly higher.
In  addition,  the  effects  of  physical  factors  can  cause  cancer. 
These factors include ionising and ultraviolet radiation. Usually 
the  physical  factors  cause  specific  forms  of  cancer;  therefore,  by 
reducing their harmful impact, it is possible to reduce significantly 
the spreading of certain forms of cancer. People working in certain 
professions can be exposed to ionising radiation, for example, 
operating  X-ray  equipment  or  nuclear  reactors.  Uranium  mining 
workers have a very high risk of cancer; for those who smoke, the 
risk increases several times. The most common diseases caused by 
ionising radiation are lung and blood cancer. Lung cancer is caused 
by inhaled radioactive dust. This dust accumulates on the lung 
surface and, in long time, may cause a malignant transformation 
of cells. People who survived the Hiroshima and Nagasaki bombing 
were at considerably increased risk of developing leukaemia.
Humans are exposed to UV radiation while outdoors. Long 
and intensive UV radiation can cause skin cancer. The intensity 

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ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
of radiation depends on the geographical location, climate and 
thickness of the layer of the stratosphere. The UV radiation 
exposure is increased in the countries with high proportion of 
clear days as well in the territories over which the ozone layer has 
been depleted. Exposure to substantial doses of UV radiation can 
also take place in specific industries and occupations, for example, 
colour coating and printing, medicine (sterilisation with UV lamps), 
welding.
Smoking and tobacco use are risk factors that have the second 
highest mortality rate. The incidence of lung cancer in smokers is 
50-20  times  higher  than  in  non-smokers.  The  death  rate  related 
to lung cancer has been growing steadily since the beginning 
of the 20
th
 century and is not expected to fall in the foreseeable 
future. Cigarette smoke contains around 4000 chemicals. There 
is evidence that many of them are carcinogenic. Smoking also 
significantly increases the incidence of mouth, larynx and bladder 
cancer.
Unhealthy eating habits also are a very important risk factor for 
cancer. People who are not on a proper and healthy diet are prone to 
the effects of carcinogenic substances. This risk may be reduced by 
means of a balanced diet and proper food preparation.
Several carcinogens significantly increase the risk of malignant 
tumour development by acting on cells, more precisely – directly on 
separate segments of the genome.
Of  the  various  causes  that  affect  the  mortality  rate  from 
malignant tumours, food and smoking are the dominant ones, and 
substances that enter the body through smoking or are ingested with 
food are the main sources of carcinogenic effects (Figure 6.11).
Infectious diseases
Unknown factors
Smoking
Alcohol
Eating habits
Food additives
Reprodutive factors
Working environment
Pollution
Medicine
Geophysical factors
Factors that can cause 
cancer are:
 
Œ inherited susceptibility. 
It is believed that 
only 5% of cancer 
incidences in the USA 
are attributable to 
hereditary genetic 
mutations in the 
human genome. In 
early childhood genetic 
factors determine the 
development of cancer, 
but it is not the main 
cause of incidences;
 
Œ environmental 
carcinogens;
 
Œ inherited susceptibility 
heightened by the 
effects of substances 
that cause cancer. 
These factors are the 
main cause of cancer 
today, accounting for 
60‑90% of cases;
 
Œ unknown factors.