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

particularly substantial. It is believed that the substances that have 
an  effect  on  the  endocrine  system  have  affected,  for  example,  the 
populations of fish and birds of prey in the Great Lakes Region, the 
population of alligators in Lake Apopka (Florida, the USA) and the 
population of otters in western Europe.
 6.3.4.  Genotoxic effects of environmental pollutants and 
factors
According  to  the  mechanism  of  toxic  effects,  three  groups 
of substances can be distinguished: mutagens, carcinogens and 
teratogens. Their effects are related to cell metabolism processes and 
impact the transmission of genetic information (Figure 6.10).
Carcinogenic substances
Somatic cells
Mutations
Diseases during
lifetime
Recombinations
Malignant
tumours
Mutations
Mutagenic substances
Germ cells
Diseases and defects
in the next generations
Teratogenic substances
Embryonic cells
Malignant
tumours
Hereditary
diseases
Transplacentary
carcinogenesis
Embryo development
disorders
Mutagenic  substances  or  factors  cause  mutations  –  heritable 
changes in the cell genotype. They can be chemical substances or 
physical factors, such as ionising radiation. Mutations that occur in 
generative cells are generative mutations, and they result in mutant 
organisms. Mutations in somatic cells occur in few body parts.
Environmental estrogens 
are
 
Œ pesticides – the 
estrogenic activity of 
many pesticides has 
been proven (DDT, 
endosulphan, dieldrin, 
kepone, dicofol, 
toxaphene, chlordane, 
alachlor, atrazine, 
nitrophen, benomyl, 
mancozeb, aldicarb);
 
Œ substances used 
in manufacturing 
polymers (bisphenol A, 
phthalates);
 
Œ therapeutic substances 
(diethylstilboestrol, 
cimetidine);
 
Œ chemicals of domestic 
use (surfactant 
degradation products – 
nonylphenol and 
octylphenol);
 
Œ many environmental 
pollutants  (poly chlori‑
na ted  biphenyls, 
dioxins, polyaromatic 
compounds);
 
Œ heavy metals and their 
compounds (lead, 
mercury, cadmium).
Figure 6.10. 
Effects of 
mutagenic, carcinogenic 
and teratogenic 
substances on living 
organisms

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6. Action of toxic substances in the environment – basic concepts of ecotoxicology 
 113
Mutations can also occur when a substance becomes ‘trapped’ 
between the chains of a DNA double helix. This situation may either 
destroy  the  conformation  of  the  DNA  double  helix,  or  cause  an 
erroneous reading of information from it.