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

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 6.3. 
 Effects of pollutants and physical factors 
on humans and ecosystems
 6.3.1.  Types of toxic effects
Although the changes that can be caused by the action of a toxic 
substance vary, it is possible to highlight some of the prevailing 
forms of toxicity.
The normal functioning of a human body is closely related to 
the environ ment. The prerequisites for life are twofold: a continuous 
exchange of substances, energy and information between the 
organism and the environ ment and the organism’s ability to distance 
itself from the environ ment to such an extent that the changes in 
environ mental  physical  and  chemical  parameters  cannot  signi fi-
cantly affect the basic life processes.
Any living organism (including a human being) is an indivisible 
unity of cells, tissues and organs. 
Regulatory mechanisms provide for the functional unity of 
various  tissues  and  organs,  and  specific  defence  mechanisms  are 
responsible for the organism’s relative independence from the effects 
of various external environmental factors:
 
Š
homeostasis – the organism’s ability to maintain the internal 
environment and various bodily functions in a stable state in 
the changing internal and external environmental conditions. 
Homeostasis is regulated by the complex self-regulatory 
mechanisms of the organism;
 
Š
adaptation  –  the  ability  of  living  organisms  to  adapt  to 
changing circumstances of existence developed in the evolu-
tionary process. The organism’s adaptation processes comprise 
various systems of organs, but the regulatory mechanisms of 
the nervous and hormonal systems are the most significant.
Although  several  stages  can  be  distinguished  within  the 
adaptation process, when the environ mental conditions drastically 
change, bodily function disorders followed by complex adaptation 
reactions  mostly  occur  first.  The  organism  is  actively  looking  for 
a  suitable  state  to  meet  the  new  circumstances.  After  that  (in  a 
favourable situation), the functions stabilise because the adaptation 
has taken place.
If foreign chemical substances enter the body, the adaptation 
process  reinforces  the  activity  of  enzymes  –  they  transform  and 
destroy the chemical substances.
If  the  effects  of  environ mental  factors  exceed  the  organism’s 
adaptive capacity, it is broken down, initiating the exhaustion 
phase in which compensatory mechanisms start their action 
against the onset and progression of a pathological process. The 
Depending on the type 
of damage caused to 
organisms, the effects of 
toxic substances can be 
categorised as follows:
 
Œ direct toxic effects: 
tissue damage;
 
Œ changes in biochemical 
reactions;
 
Œ neurotoxic effects;
 
Œ immunotoxic effects;
 
Œ mutagenic effects;
 
Œ genotoxic effects;
 
Œ carcinogenic effects;
 
Œ effects on the 
endocrine regulation 
processes.

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108 
ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
effects  of  adverse  environ mental  factors  and  pollution  depend 
mainly on the organism’s health condition, age and sex. Children 
and elderly people are much more sensitive to the harmful effects 
of pollutants than adults. This also applies to pregnant women 
and their unborn children, sick people and people with different 
pathological conditions, such as nutritional deficiency diseases and 
avitaminosis.
To fight the effects of adverse environ mental factors, the body 
has developed several defence systems that ensure its ability to resist 
these adverse impacts. The skin and mucous membranes, the organs 
located on the boundary between the environ ment and organism 
(respiratory and digestive systems, the lymphatic system and urinary 
tract) as well as the immune system, mononuclear phagocytic system 
and defence reflexes perform the barrier function.
The purpose of immunoprotection is the organism’s defence 
against genetically foreign cells and substances. The lymphatic 
tissue and organ systems perform the organism’s immunoprotection.
The defence functions of the respiratory system are as follows: 
ciliary movement in the bronchial epithelium and excretion of mucus 
from the bronchial glands, bronchial muscle contractions, activity of 
the pulmonary macrophage system, secretion of immunoglobulins 
from the airway mucosa and stability in the pulmonary alveoli 
provided by a complex system of self-regulating surfactants.
In the process of evolution, the organism’s defence system has 
effectively  developed  to  combat  naturally  toxic  substances  and 
other adverse factors. However, the environ mental pollution also 
contaminates the internal environ ment of the human body. Dust 
accumulates in the lungs, metal compounds are deposited in the 
bones, soft tissues and organs. Contamination in the human body 
initiates changes in the physical and chemical parameters of the 
organism’s  internal  environ ment.  A  considerable  contamination  of 
the environ ment and organism can disturb the functioning of the 
organism’s defence system. 
If the harmful environ 
mental conditions are excessively 
hazardous or persist for longer periods of time, exceeding the 
organism’s adaptability, they become the risk factors for a variety of 
pathological conditions, illnesses or even death.