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Their accumulation in the body led to a reduction in the seals’ resistance to
infection. Thus, without directly causing death of the animals, the pollutant
significantly increased their sensitivity to the effect of other adverse environmental factors. This form of ecotoxic effect is seen in the case of an increase
in the development of neoplasms, and a reduction of reproductive function
in populations of people living in the regions of South Vietnam, contaminated with ecotoxicants from warfare.
Embryotoxic effects of ecopollutants refer to the impact of various xenobiotics (including medicinal substances) on human and other mammalian
embryos, as well as on the eggs of monotremes, insects, birds, reptiles and
amphibians. For example, the accumulation of DDT in the tissues of birds,
such as mallard, osprey, bald eagle, etc., leads to thinning of the eggshell,
disruption of embryonic development and unhatched eggs. This is accompanied by a reduction in bird populations.
The toxic effect of many xenobiotics is due to the direct toxic effect of
metabolites of the xenobiotic. Field observations of freshwater viviparous
fish in Florida revealed populations of a large number of females with signs
of masculinization in peculiar behavior, modification of fins, etc. These populations were found in a river below the wastewater flow of a nut processing
plant, the effluents of which did not contain any masculinizing substances.
However, the wastewater of the plant contained phytosterone, formed
during processing of the raw materials. Subsequently, biotransformation of
phytosterone by some bacteria in the river produced androgens (Fig. 5.3),
which caused the masculinization effect in these fishes.
Fig. 5.3. Conversion of phytosterol into androgen by microorganisms
The indirect toxic effect by reduction of food resources in an ecosystem
was experienced in Canada, where the forestry application of organophosphorus pesticides to control caterpillars and insects resulted into a sharp
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decline in the number of caterpillars and insects. This caused millions of
birds to die from starvation.
Population explosion due to destruction of competitive species: After
the use of synthetic pesticides to control some plant pests in the United States,
a previously small number of cotton mite species began to multiply intensively. This phenomenon is based on the fact that, the use of the synthetic
pesticides resulted in the death of predators of cotton mite. Thus, the ecotoxic effect of xenobiotics in the environment can result in the destruction of
the natural population control systems in an ecosystem.
Q u e s t i o n s & A s s i g n m e n t s
1. Discuss the concept of ecotoxicology.
2. Describe the xenobiotic profile of an environment.
3. Explain the role of abiotic transformation of ecotoxicants.
4. Explain the principles of biotic transformation of xenobiotics.
5. Outline the mechanisms of bioaccumulation.
6. What are the reasons for biomagnifications?
7. What is ecotoxicokinetics?
8. What is ecotoxicodynamics?
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C O N C L U S I O N
The development of industry is inextricably linked with the expansion
of the range of chemicals being used currently for various purposes. Modern
development of production and agriculture is characterized by rising applications of pesticides, fertilizers and other chemical substances. This is the objective reason for the steady rise in chemical hazard to the environment,
which lurks in the very nature of human activity.
Modern scientific, technical and socio-economic development involves
processes of excessive exploitation of natural resources; degradation of ecosystems; high generation, disposal, and accumulation of waste. These situations lead to increasing environmental risks and undermine public health.
Indeed, chemical substances from industrial activity that disrupt the
equilibrium of ecosystems are inevitably released into the biosphere. Besides
industry, some of the very serious environmental disasters in human history
are associated with chemical warfare. Environmental and economic policies
in different countries of the world must redefine economic activity in an environmentally acceptable manner towards transition to socio-ecological satisfaction of material needs. The transformation of xenobiotics in the environment under conditions of external influence is a natural process of removal
of toxicants from ecosystems. Nevertheless, the products of some of
the transformation processes tend to be even more toxic than their initial parent substances.
Thus, toxicology occupies an important position in the block of natural
science disciplines, taught to future environmental engineers and chemical
technologists. The subject explores the principles of interaction between living organisms and toxicants; identification of the mechanisms of toxic effects
of harmful substances; and the characteristics of different forms of pollution
of the biosphere. This knowledge is important for the achievement of sustainability of common practical activities, as well as applications of scientific
advancement.
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L I T E R A T U R E
1. Albert, A. Selective toxicity / А. Albert. – London, New York: Chap-
man and Hall, 1985. – 565 p.
2. Gupta, P. K. Fundamentals of Toxicology. Essential Concepts and
Applications / P. K. Gupta. – Academic Press is an imprint of Elsevier,
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Royal Society of Chemistry, 2006. – 516 p.
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Wolff F. A. Basic analytical toxicology. World Health Organization, 1995. –
274 р.
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Toxicol. Industr. Health. – 1997. – V. 13. – P. 163-192.
7. Miller T. Living in the Environment: Principles, Connections,
and Solutions. Cengage Learning, 2006. – 784 р.
8. Исидоров, В. А. Введение в химическую экотоксикологию /
В. А. Исидоров. – Санкт-Петербург: Химиздат, 1999. – 142 с.
9. Куценко, С. А. Основы токсикологии / С. А. Куценко. – Санкт-
Петербург: Фолиант, 2004. – 720 с.
10. Курляндский, Б. А. Общая токсикология. / Б. А. Курляндский,
В. А. Филов. – Москва: Медицина, 2002. – 607 с.
11. Химическая безопасность и мониторинг живых систем на
принципах биомиметики / Г. К. Будников, С. Ю. Гармонов, Э. П. Медянцева, Г. А. Евтюгин – Москва: ИНФРА-М, 2013. – 320 с.
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EDUCATIONAL EDITION
ОСНОВЫ ТОКСИКОЛОГИИ
Editor L. Shevchuk
Computer layout – A. Rakhmankulova
Sergey Garmonov
Lawrence Nugbienyo
FUNDAMENTALS OF TOXICOLOGY
Сергей Юрьевич Гармонов
Лоуренс Кабла Адану Бамиделе Нугбиеньо
95
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