Экологическая медицина = Ecological medicine. Учебное пособие

Task 4. Estimate the total air pollution in point A of city H by the level of average annual concentrations of 5 substances (Table 7).

Table 7. Determination of the total index of atmospheric air pollution

Algorithm for solving problems to assess the degree of atmospheric air pollution. Hygienic assessment of the danger level of atmospheric air pollution with the simultaneous presence of several harmful chemical substances in the air is carried out by the value of the total pollution index “P”, which takes into account the frequency of exceeding LOC, hazard class of the substance, the number of co-pollutants in the atmosphere. The index “P” considers the nature of the combined action of harmful substances on the type of incomplete summation.

It should be remembered that the index “P” is conditional, due to the fact that with prolonged intake of atmospheric pollutants into the human body the nature of their combined action in most cases is still unknown and its quantitative expression is as close to the possible biological effects. Calculation of the complex index “P” is carried out by the formula:

Pi = n ∑Ki ,

where, Pi – the total index of pollution; Ki – concentrations of substances of hazard class 1, 2, 4 “normalised” according to LOC, “reduced” to that of biologically equivalent hazard class 3, according to isoefficiency coefficients.

The modern algorithm for calculating the complex index of atmospheric air pollution uses the following isoefficiency coefficients to “bring” the

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concentrations of substances of different hazard classes normalised according to the Threshold Level Value continuous exposure to those of the 3rd hazard class: Class 1 — 2.0; Class 2 — 1.5; Class 3 – 1.0; Class 4 – 0.8.

The actual air pollution of populated areas is estimated depending on the index “P” value in five steps: I is permissible, II is weak, III is moderate, IV is strong, V is dangerous.

Pollution of the I degree is safe for public health. When there is pollution of the II-V degree, the occurrence of negative effects will rise with an increase in the degree of atmospheric pollution.

When calculating “P”, the actual concentrations and LOC of the same averaging periods are used. At the same time, the index “P” has the same time characteristic. An example of calculating the total indicator of atmospheric air pollution is shown in Table 8.

A list of harmful substances determined in a given territory is compiled. The hazard class of each substance and the average concentration (mg/m3) are indicated. The frequency of exceeding Threshold Level Value continuous exposure is established. Then using the isoefficiency coefficients, exceeding Threshold Level Value continuous exposure of substances of different hazard classes are “brought in line” with exceeding Threshold Level Value continuous exposure of substances of the 3rd hazard class.

Table 8. Example of calculating the total index of atmospheric air pollution “P” by annual average concentrations

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Chapter 5

MEDICAL AND ECOLOGICAL CONSEQUENCES

OF HYDROSPHERE POLLUTION

Motivational characteristic of the topic. Understanding the early signs of the toxic effects of the main substances polluting the hydrosphere is necessary for targeted identification and elimination of hydrosphere pollution sources and prevention of adverse effects of xenobiotics on the human body.

Fresh water pollution has become an acute problem of our time. Population growth and progressive development of various industries lead to increasing pollution of rivers, lakes and other water bodies. Many of the substances that make up wastewater are toxic to humans and living organisms­ .

The objective: to understand the cause-and-effect relationship between the state of the hydrosphere, the quality of drinking water and the development of pathology in humans.

Tasks:

1.  To understand the environmental and health consequences of ­hydrosphere pollution.

2.  To understand the peculiarities of the effects of waterborne pollutants on children’s and adults’ bodies.

3.  To learn how to assess the carcinogenic risk for public health when drinking water containing substances with carcinogenic effect.

Requirements for students’ initial knowledge level. To fully master the topic of the chapter, a student should revise the relevant material from the following disciplines:

1.  General and Bioorganic Chemistry: “Chemicals polluting water; methods of qualitative and quantitative determination; stages of mineralisation of organic substances; properties of oxidants”.

2.  The Normal Human Physiology: “Basic physiological functions of water, its role in maintaining the vital functions of the body, water-salt metabolism”.

3.  Microbiology, Virology, Immunology: “Water is the habitat of microorganisms, sources of contamination; sanitary and microbiological methods of water research”.

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Review questions from the related disciplines:

1.  Hydrosphere: definition of the concept, composition.

2.  The influence of human activity on the hydrosphere state.

3.  The concepts of “heavy metals”, “microand macro elements”, “fertilisers”, “pesticides”.

4.  Sources of heavy metals in drinking water.

5.  What determines the solubility of metals in water?

Questions related to the topic of the chapter:

1.  The origin and functions of water on Earth. General characteristics and types of hydro-ecosystems.

2.  Factors and sources of natural and anthropogenic pollution of the hydrosphere.

3.  Eutrophication of reservoirs: concept, causes of development, consequences.

4.  Environmental assessment of water resources in Belarus. Diseases associated with water pollution by living organisms.

5.  Characteristics and peculiarities of xenobiotics that enter human body with water, including neurotoxicity and nephrotoxicity features.

6.  Characteristics of the main xenobiotics contained in water: lead, cadmium, fluorine, chlorine, volatile organic compounds (VOCs). Specific early signs of their effects on the human body.

7.  Diseases related to the consumption of chemically contaminated water. The main ways to reduce the content of xenobiotics in drinking water.

8.  Environmentally dependent morbidity of the population. Criteria for the quality of drinking water.

LEARNING MATERIAL FOR THE CHAPTER

The hydrosphere is defined as the aggregate of all water bodies of the globe, including oceans, seas, rivers, lakes, reservoirs, marshes, groundwater, glaciers, snow cover, and rock-liquid water that is part of the atmosphere. In the most general form, the hydrosphere is divided into oceans, continental waters, and groundwater.

The total volume of water reserves on the planet is 1.4 billion km3. Of all this volume, 91–92% is salty sea water, which contains about one teaspoon of salts per glass of water. The ice contained at the poles and in the mountains is another 2.2%. Fresh water of rivers, lakes, underground aquifers is only 0.6%. The rest is water vapour in the atmosphere.

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Water serves not only to meet the ecological, physiological and sani- tary-hygienic needs of people, but is equally necessary for livestock, agriculture, various industries, energy, services, transport links, which affects the quality of water.

The human drinks up to 75 tons of water in their lifetime. The WHO estimates that up to 80% of diseases are somehow or other water-related. Epidemics and pandemics of infectious waterborne diseases were particularly rampant in the past, but even today millions of people suffer and die from water-related diseases (malaria, cholera, typhoid, viral hepatitis, schistosomiasis, filariasis, etc.). The damage to various hydraulic structures (including water pipelines) causes great harm to public health. This was the reason for 20.4% of deaths, reported in Japan within 10 years after World War II, to be due to waterborne infections. And in 1956, in Delhi, India, an outbreak of hepatitis A occurred as a result of contamination of the drinking water supply system, affecting more than 50,000 people. According to one hypothesis, among the reasons that contributed to the fall of the Roman Empire was poisoning of the population with lead, the source of which was water pipes and vessels for drinking water and wine.

Since the bulk of the water is concentrated in ocean-type reservoirs, the properties of the aquatic medium are usually considered on the basis of the world ocean. The ocean occupies 71% of the Earth’s surface, while inland waters account for only about 5%.

Continental water bodies retain the most fundamental properties of the aquatic medium, differing from the world ocean system by shallower depths and a greater range of salinity. As for the mobility nature of water masses, there are standing and circulating (flowing) water bodies. Standing water bodies (lakes, ponds) are divided into fresh and saline. Many continental reservoirs exceed oceanic waters in salinity.

Underground water sources penetrate the thickness of the Earth’s crust to a depth of about 13–14 km. Characteristic features of groundwater are:

yyclose contact with the soil and rocks of the Earth’s crust;

yylayered locations of water horizons, separated by waterproof layers of solid rocks;

yyweak connection with the atmosphere (poor aeration);

yypoor development of biological processes and poverty of life forms; yypresence under conditions of high temperature and pressure. Groundwater is more often benign. Being located at different depths,

they have a more stable composition, contain more substances useful for the human body (calcium, iodine, fluorine), are less polluted by sewage, microorganisms.

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Interstratal pressure waters are the most reliable in terms of ecology and hygiene. Their thickness can be from 14 m to 36 m. They are more mineralised than groundwater and, as a rule, free from microorganisms.

The main problems associated with the hydrosphere of the planet are the conditions of water supply to the population, its quality and the possibility of its improvement. Water resources are the most vulnerable component in relation to the anthropogenic impact of the environmental component. About 2/3 of surface waters in the CIS do not meet regulatory requirements. The greatest threat to water resources is the deteriorating quality of natural waters.

The main sources of pollution are: wastewater from industrial, muni­ cipal and agricultural enterprises; atmospheric precipitation; surface runoff of pollutants from agricultural and residential areas (this uncontrolled areal run-off contributes up to 50% of the total volume of pollutants entering water bodies).

According to the volume of wastewater discharged, the industries are ranked as follows:

1)  chemical and petrochemical industry;

2)  lumber and paper industry;

3)  energy;

4)  building materials industry;

5)  mechanical engineering;

6)  ferrous metallurgy;

7)  non-ferrous metallurgy.

The most common pollutants are sulphates, chlorides, ammonium nitrogen, total nitrogen, nitrates, total phosphorus, petroleum products, phenol, easily oxidizable organic substances, compounds of iron, copper, zinc, synthetic surfactants, specific organic substances (lignin, lignosulphonates, methyl mercaptan, aniline, organochlorine pesticides).

There are various chemical compounds, such as fertilisers coming from fields into water bodies, and phosphates contained in a number of detergents, washing powders, etc. These components are a source of biogenic elements which saturate the water, leading to the phenomenon of increasing biological productivity (the eutrophication phenomenon) of water bodies. The subsequent development of blue-green algae is accompanied by a shift in the ecological equilibrium and its gradual swamping, i.e., death.

Environmental Assessment of water resources in the Republic of Belarus.

Belarus belongs to the regions where water supply of almost all major settlements and industrial enterprises is fully or partially carried out by

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groundwater. Currently, the register of drilling wells in Belarus includes several tens of thousands of hydrogeological production wells. The relevance of this issue has increased especially in recent years, which is due to the following reasons:

1.Belarus is an economically developed region with a significant share of urban population.

2.The Chernobyl accident in 1986 led to radioactive contamination of a significant part of the Belarusian territory (especially within the Gomel and Mogilev regions).

3.Many rural settlements use wells to exploit the first aquifers from the surface, including groundwater aquifers. However, excessive use of fertilisers has led to contamination of these aquifers with various components.

4.Due to the high rate of human engineering activity, there is a threat of groundwater pollution, and many places are already experiencing technogenic pollution. Examples are Soligorsk and Rechitsa districts, the territory of Gomel chemical plant, etc.

All this causes the necessity of searching for and introducing new reliable sources of water supply.

The most important direction in ensuring sanitary and epidemiological well-being of the population in the Gomel region is the quality and safety of drinking water provided for the population.

According to the existing WHO classification, there are five groups of diseases related to environmental state of the hydrosphere:

1)  diseases from contaminated water (typhus, cholera, dysentery, polio, hepatitis);

2)  diseases of the skin and mucous membranes (trachoma, leprosy); 3)  diseases caused by shellfish (schistosomiasis, guinea worm);

4)  diseases caused by insects living and reproducing in water (malaria, yellow fever);

5)  diseases from contaminated water. This very extensive group of wa- ter-related diseases includes those which spread depending on the content of various microcomponents (organic and inorganic chemical compounds, trace elements, radionuclides) of natural or anthropogenic origin. It can be divided into the following subgroups: 1) acute diseases (as a rule, poisonings) caused by drinking water containing highly toxic concentrations of hazardous and harmful substances; 2) diseases caused by the consumption of foods (as a rule, hydrobionts) that contain toxic substances from the aquatic environment; 3) chronic diseases that occur with prolonged drinking water consumption, where the concentration of harmful substances is

low, or their effect is observed after a long latent period.

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According to the World Bank, approximately 1.2 billion people in the world drink environmentally unfavourable water.

With drinking water, numerous xenobiotics can enter the human body, including those that affect the nervous and excretory systems. In this regard, it is necessary to separately consider the features of neuro- and nephrotoxicity.

Neurotoxicity is the property of chemicals to cause disruption of the structure and/or functions of the nervous system. Neurotoxicity is inherent in most known substances. Therefore, almost any acute intoxication is more or less accompanied by disorders of the functions of the nervous system.

The most important condition for the direct action of a xenobiotic on the central nervous system is its ability to penetrate the blood-brain barrier (BBB). Substances that do not penetrate through the BBB will cause toxic effects on the periphery, mainly in the area of synaptic contacts of nerve fibres with nerve cells of organs, vegetative and sensitive ganglia.

The pathology developing in humans is a consequence of the effects of xenobiotics on excitable membranes, mechanisms of nerve impulse transmission in synapses, plastic and/or energy (hypoxia, ischaemia) exchange in nerve tissue.

To the greatest extent, the disruption of energy metabolism affects the state of neurons with a high level of oxygen consumption and macroerg synthesis. In general, small cells with a large number of dendrites are more sensitive to hypoxia (ischaemia) than large neurons with long axons and a small number of dendrites (motoneurons). Glial and endothelial cells are less sensitive to hypoxia (ischaemia). Among the structures formed by grey matter, the most sensitive to hypoxia are: cerebral cortex, cerebellar cortex (Purkinje cells), hippocampus.

The neurotoxic process can manifest itself in the form of impaired motor, sensory functions, emotional status, memory, learning. Vision, hearing, tactile and pain sensitivity, etc. are often impaired. Sensory disorders lead to muscle weakness, paresis, and paralysis.

Nephrotoxicity is the property of chemicals to cause structural and functional disorders of the kidneys. Nephrotoxicity can manifest itself as a result of direct interaction of chemicals (or their metabolites) with the renal parenchyma, and indirectly, mainly through changes in haemodynamics, acid-base state of the internal environment, massive formation of toxic destruction products of cellular elements in the body that are subject to excretion through the kidneys (hemolysis).

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The mechanisms of nephrotoxic action of xenobiotics are diverse and, at the same time, develop according to a fairly general scenario. The toxicant that has passed through the filtration barrier in the glomeruli is concentrated inside the tubules due to the reabsorption of most of the water contained in the primary urine. Under the influence of the concentration gradient that develops at the same time or due to the processes of active reabsorption, xenobiotics enter the cells of the tubular epithelium and accumulate there. The nephrotoxic effect develops when the critical concentration of the toxicant in the cells is reached.

Most countries have a list of the main pollutants that can have an adverse effect on the human body and whose content is regulated in drinking water. Their list and permissible concentrations may differ considerably. In the Republic of Belarus, the main document regulating the content of harmful components in drinking water is Sanitary Rules and Regulations 10–124 RB 99 “Drinking Water. Hygienic requirements to the quality of water of centralised drinking water supply systems. Quality Control”.

Negative consequences of anthropogenic interference in the processes of water exchange in the biosphere. Proper diagnosis, treatment, and prevention of diseases associated with the impact of environmental factors require the practitioner to know the basics of hygienic diagnosis and clinical picture of known environmentally caused diseases. If there are symptoms or syndromes that allow suspecting the influence of environmental factors, the doctor, during the anamnesis collection, should pay attention to all possible risk factors (contact with harmful factors at home, at work, etc.). If necessary, the doctor should request additional data on the quality of water, air, working conditions from the territorial centre of hygiene and epidemiology.

There are well-known diseases associated with water pollution, the socalled eco-dependent diseases:

–  Minamata disease (mercuriosis). Minamata disease was first registered in the 1950s, when 292 people fell ill with it and 62 of them died. The disease was characterised by visual, hearing, touch, and neurological disorders. Congenital malformations were registered in newborns. In 1969, it was found that the disease was caused by methylmercury, which entered Minamata Bay with the waste products of the Nippon Chisso factory and concentrated in marine organisms and fish that served as food for the population. In 1974, 7,000 cases of poisoning were detected here. Mercury is actively accumulated by plankton as food for crustaceans, which, in turn, serve as food for fish. For example, pike caught off the Swedish coast

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