Экологическая медицина = Ecological medicine. Учебное пособие

The biodegradation of substances on Earth, including the vital activity of soil bacteria, leads to the formation and removal into the atmosphere of large amounts of hydrogen sulphide, ammonia, hydrocarbons, nitrogen oxides, carbon monoxide and dioxide.

As a rule, natural pollution does not threaten to have negative consequences for biogeocenoses and the living organisms there in, although short-term consequences are possible.

Sources of anthropogenic inputs into the atmosphere are heat production, industry, oil and gas refining, transportation, and testing of thermonuclear weapons.

Each of these sources (and each branch of production) is associated with the release of specific impurities, the composition of which includes tens of thousands of substances, but their identification is sometimes difficult. However, the most common pollutants entering the atmosphere in large quantities, and therefore called multi-tonnage, are relatively few. The most common industrial emissions are as follows: ash, dust, nitrogen oxide and dioxide, ammonia, sulphur dioxide and trioxide, hydrogen sulphide, mercaptan, aldehydes, hydrocarbons, resins, carbon oxide and dioxide, fluoride, radioactive gases, aerosols.

The largest amount of air pollutants is emitted with vehicle exhaust gases. Petrol engines emit more unburned hydrocarbons and incomplete oxidation products (carbon monoxide and aldehydes) than diesel engines. Each car with a petrol engine consumes 4,350 kg of oxygen for the 15,000 km, and emits 3,250 kg of carbon dioxide, 350 kg of carbon monoxide, 93 kg of hydrocarbons, 27 kg of nitrogen oxides.

Thermal power plants emit gases containing sulphur and nitrogen oxides,­ ash, metals into the atmosphere; ferrous metallurgy enterprises emit gases including dust, sulphur and metal oxides.

One ton of steelmaking pig iron accounts for 4.5 kg of dust, 2.7 kg of sulphur oxide, 0.1–0.5 kg of manganese, as well as compounds of arsenic, phosphorus, antimony, lead, mercury, resinous substances.

The greatest air pollution is owed to oxides of carbon, sulphur and nitrogen compounds, hydrocarbons and industrial dust. Within a year, about 200 million tons of CO, more than 20 billion tons of CO2, 150 million tons of SO2, 53 million tons of SO, more than 250 million tons of dust, 120 million tons of ash, more than 50 million tons of various hydrocarbons are emitted into the Earth’s atmosphere.

The progressive saturation of the biosphere with heavy metals is one of the most significant global consequences of the scientific and technological

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revolution­ . It is estimated that throughout the history of human society about 20 billion tons of iron have been smelted. The amount of iron in structures, machinery, equipment, etc. is now estimated at about 6 billion tons. Consequently, about 14 billion tons are dispersed in the environment, other metals are dispersed even more. For example, the dispersion of mercury and lead is 80–90% of the annual production. When burning coal with ash and waste gases, some elements enter the environment more than they are extracted from the subsoil: magnesium – by 1.5 times, molybdenum – by 3 times, arsenic­ – by 7 times, uranium, titanium – by 10 times, aluminium – by 15 times, mercury – by 50 times, germanium – by thousands of times.

Chemical transformation of substances in the atmosphere. Air pollutants are divided into primary and secondary. The primary ones are those that are contained directly in the emissions of enterprises and come with them from various sources, and the secondary ones are the products of the transformation of primary or so–called secondary synthesis, and these products in many cases are much more dangerous than primary substances.

Chemical compounds released into the atmosphere undergo a wide variety of transformations as a result of reactions between them as well as with substances already contained in the air, including water vapour, and also under the influence of sunlight.

The most significant transformations are under the effect of solar radiation. For atmospheric photochemistry, the phenomena of photochemical dissociation of electronically excited molecules are of the greatest interest, as a result of which undesirable compounds arise, including those that serve as the basis of photochemical smog.

Chemical transformations in the troposphere and stratosphere are ­initiated mainly by the products of photolysis of molecules such as О3, О2, Н2О, N2О, NО2. Ozone is the most important component determining the chemistry of the stratosphere. In addition, there are five main nitro- gen-containing gases in the atmosphere: N2, NН3, NО, N2О, NО2. In the condensed phase, nitrogen is present in the form of an ammonium ion and a nitrate ion. There is a significant number of organic nitrates in the atmosphere of cities.

Nitrogen oxides of anthropogenic origin in most cases enter the atmosphere in the form of NO. The cycle of nitrogen compounds in the troposphere is supplemented by the formation of nitric acid, which can react with metal ions to form nitrates.

Atomic oxygen and ozone are able to enter into compounds with various organic substances, resulting in radicals. The presence of free radicals

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leads to smog formation. The main products of these photochemical reactions are aldehydes, ketones, CO, CO2, organic nitrates and oxidants.

Physical and environmental consequences of atmospheric pollution. Due to the atmosphere pollution, there are problems associated with a decrease in its transparency and reduced visibility, as well as with the appearance of unpleasant odours and dustiness. Air pollution poses a threat to human health and the normal functioning of ecological systems.

The energy balance of the planet changes due to changes in the albedo (reflectivity) of the earth’s surface, the transparency of the atmosphere and the release of a large amount of heat. The albedo changes during the cultivation of vegetation of a certain nature, as well as during irrigation or drainage of the Earth’s surface.

Atmospheric dustiness affects the reflectivity of the Earth. The hygienic standard of the atmosphere allows a total dust content of 1.5 t/ha, and in some industrial areas it reaches 60 t/ha. Dustiness of the atmosphere increases the amount of reflected solar radiation and reduces the amount of radiation reaching the Earth, which leads to a cooler climate. At the same time, dust falling on the surface of glaciers absorbs solar energy, contributing to their melting.

The accumulation of carbon dioxide in the atmosphere is the key in changing air transparency. Every year, the amount of CO2 in the atmosphere increases by 0.4% of its total content. At present, the volume fraction of CO2 in the atmosphere is 0.035%. The CO2 content in the atmosphere is believed to double every 23 years. Carbon dioxide absorbs infrared thermal radiation, which at a certain concentration can lead to a global temperature increase.

The amount of ozone in the atmosphere is small (2×106% by volume), but it plays an important role in protecting the Earth’s surface from the ultraviolet part of the solar spectrum. The ozone layer destruction occurs as a result of ozone oxidation of various substances, including combustion products of aircraft and rocket fuels. This threatens to increase the dose of ultraviolet radiation reaching the Earth’s surface. According to some data, the destruction of the ozone layer by 50% will entail an increase in the ultraviolet dose by a factor of 10.

The process of ozone layer depletion has been observed since the beginning of the 1970s and has recently been called “ozone holes”. If we concentrate all ozone in a conditionally continuous layer, its thickness will not exceed 3 mm.

Studying the causes of ozone reduction in the atmosphere showed that the major of them is high concentration of chlorine monoxide (ClO) in the

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atmosphere, and there is a clear correlation between ClO content and decrease in O3 content.

The main source of chlorine in the atmosphere is considered to be freons – fluorine and fluorocarbons, such as Freon 12, widely used as refrigerating agents.

The most acute problem is the atmosphere pollution with sulphur-con- taining substances. Sulphur dioxide has a harmful effect on plants. When it enters the leaf during respiration, SO2 inhibits the vital activity of cells. It causes the leaves to first turn brown and then wither away.

Sulphur dioxide and other sulphur compounds irritate the mucous membrane of the eyes and respiratory tract. Prolonged exposure of low concentrations of SO2 leads to chronic gastritis, hepatopathy, bronchitis, laryngitis and other diseases. There is evidence of a link between the SO2 content in the air and the death rate from lung cancer.

The construction of high smokestacks helps to transfer SO2 over long distances and disperse it in the upper layers of the troposphere, reducing local air pollution. This method, designed for air natural self-purification due to dispersion, results in increasing the residence time of sulphur-containing compounds in the air, and consequently, increasing the degree of their conversion into sulphuric acid and sulphates. Sulphur dioxide (combined with water mist) is a major component of sulphur smog, sometimes called London smog, as the residents of that city first suffered severely from it in 1952.

Acidic precipitation (rain and snow), also known as acid rain, causes significant damage to water and soil quality. The burning of coal, oil, and gas converts much of the sulphur they contain into sulphur dioxide, while atmospheric nitrogen reacts with oxygen to form nitrogen oxides, which then combine with atmospheric moisture to form sulphuric and nitric acids that precipitate with rain or snow.

The acidity of normal rainwater is 5.6. There are cases when the acidity of precipitation reached 2.3 (the acidity of lemon juice). Such precipitation negatively affects the needles and foliage of trees, as well as the green assimilation apparatus of herbaceous plants, lead to water acidification, suppressing the populations of many aquatic organisms, as well as causing soil acidification.

Millions of tons of acids precipitate annually, leading to a radical change in the chemistry of the natural environment.

Atmospheric air quality and public health. Atmospheric emissions can change the chemical composition of air to such an extent that there is a real danger to human health. This risk is determined by the following factors:

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1.  Wide and increasing opportunities for air pollution. According to scientists, the potential threat from toxic waste is second only to the threat of nuclear war for civilisation. On average, in developed countries, the annual damage from air pollution ranges from about 15 to 150 dollars per person.

2.  A variety of contaminants. It is believed that the health of a person living in an industrial area is at risk of exposure to several hundred thousand chemicals. This can lead to a potentiating action when their effect is summed up.

3.  Unusual conditions for the human body. Humans evolved in an unchanging air environment, and only in the last few hundred years have they been exposed to different conditions with respect to air composition. Chemicals are created with which they have never encountered before and to which they are vulnerable.

4.  The possibility of massive intake of harmful substances. Even at a concentration of 1 mg/l, a huge amount of toxicant can enter the body (12,000 litres of air per day are inhaled at rest, i.e., 12 g of substance), 80% of occupational poisoning and 60% of infectious diseases occur aerogenically.

5.  Wide and immediate access of pollutants to the internal environment of the body, the absence of a detoxification barrier. The lungs have a surface area of about 100 m2, the air enters almost in direct contact with blood, and nearly everything in the air dissolves in the blood. From the lungs, the blood goes directly into the systemic circulation, the CNS and other organs, bypassing a barrier such as the liver. It was found that a poison through the lungs acts 80–100 times stronger compared to its ingestion through the gastrointestinal tract.

6.  The difficulty of protection and the inevitability of the action. It is impossible to stop breathing. You can refrain from consuming bad water and food, but not from the air, as noted above. Air pollution acts universally, i.e., it affects all population groups, including children, the sick, and the elderly, and it happens around the clock.

7.  Slow, imperceptible, but constant action of atmospheric pollution on humans. This leads to underestimation of the danger; people take measures to protect the air poorly and belatedly; air health legislation in most countries lags behind that for water and food protection.

It is now firmly established that the increased content of certain gases and aerosols in the atmospheric air under certain conditions can have an adverse effect on human health. The following types of action of atmospheric

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­pollutants on the body are possible: acute poisoning, chronic poisoning, metatoxic action, promoter action.

The most adverse acute effects of exposure to atmospheric pollution on the health of the population are manifested in an increase in mortality, often accompanying even a short-term increase in the level of such pollution. The most pronounced effect is observed in relation to mortality from respiratory pathology. The eco-hygienic analysis allows to establish the connection between increases in concentrations of atmospheric pollutants and the frequency of hospitalisation of patients with respiratory and cardiovascular diseases.

Toxic fogs are a typical example of the acute action of atmospheric pollutants. Chronic effects can be specific or non-specific. Chronic specific action can be caused by such pollutants as fluorine, beryllium, lead and arsenic compounds, etc. Atmospheric air pollutants play a role in the development of long-term effects, such as carcinogenic, embryotropic, teratogenic, gonadotoxic and mutagenic effects. The chronic non-specific effect­ is expressed in the weakening of protective forces, deterioration of physical development of children, increase of general morbidity.

During toxic fog (smog), air pollution with soot and sulphur compounds increases dramatically. Smog occurs especially easily with temperature inversion, which occurs on clear days as a result of the cooling of the earth due to radiation. Because of the temperature inversion, all the pollution creeps along the ground, especially in windless weather. During smog, people suffering from chronic respiratory and cardiovascular diseases are particularly affected and most often die.

Chronic poisoning is much more common, but it is poorly recorded. The WHO recommends paying attention to the metatoxic effect, especially when taking into account the incidence of chronic bronchitis, which is a sensitive indicator of air pollution. Chronic respiratory diseases are becoming one of the main causes of death in the United States. Mortality from emphysema of the lungs and chronic bronchitis has increased more than 4 times over the past 10 years.

When examining the health status of the population exposed to polluted air, especially significant changes are observed in children. The children living in the impact zone of metallurgical plant emissions suffer twice as often from upper respiratory tract diseases than the children of the control (clean) district. Many children living near the plant had atrophic lesions of the nasal mucosa and inflammatory processes in the nasopharynx. They

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lagged behind in physical development. X-ray examination of children in the contaminated area revealed presilicoic changes in the lungs.

Child health studies are often conducted to rule out the effects of smoking and occupational hazards. Typically, these studies show that children living and attending school in air-polluted areas have poorer lung function and suffer from infectious respiratory diseases more frequently and more severely than children living in areas with cleaner air.

As for the promoter action, the incidence of malignant neoplasms, ­especially of the lungs, is currently associated with atmospheric pollution. The danger of increasing the incidence of malignant neoplasms of the upper respiratory tract is confirmed by direct animal experiments, indicating the carcinogenic and cocancerogenic properties of exhaust gases of automobile engines, tobacco smoke, phenol and other compounds. Benz(a)pyrene has particularly strong carcinogenic properties.

Many of the substances artificially created by humans have not only carcinogenic, but also mutagenic and (or) teratogenic properties. They are able to change the genetic or hereditary material of cells and thus cause mutation or, by interfering with the normal development of the embryo, lead to the appearance of congenital deformities, i.e., have a teratogenic effect. Finally, a number of substances contained in atmospheric air for example O3, have a radiomimetic effect similar to the effect of ionising radiation. In animal experiments, the radiomimetic effect of O3 is manifested in premature ageing of animals, as well as in an increase in the number of cases and the development of lung diseases.

Atmospheric pollution control measures can be divided into groups: planning, scientific, technical and legislative. To a greater or lesser degree, they are provided for in all countries of the world, but the effect is often far from the desired one due to various reasons related to the specifics of one or another state.

PRACTICE

Determine the amount of anthropogenic pollution entering the environment as a result of motor transport. Choose a 0.5–1 km highway section near the school that has a good visibility. Measure the section length (in metres), having previously determined the length of your step.

Determine the number of vehicles passing through the section for 20 minutes, 1 hour. In doing so, fill in Table 1.

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Table 1. Assessment table

The amount of emissions of harmful substances is calculated. The input data are:

yythe number of vehicles passing through the allocated section per time unit;

yyfuel consumption rates for motor vehicles when driving in urban conditions (Table 2).

Table 2. Fuel consumption rates

The values of empirical coefficients (K) determining the emission of harmful substances from motor vehicles, depending on the type of fuel, are shown in Table 3.

Table 3. Emission coefficients

The K coefficient is numerically equal to the amount of harmful emissions of the corresponding component when the amount of fuel equal to the specific consumption (l/km) is burned in the car engine.

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Processing the results and conclusions. Calculate the total distance travelled by the identified number of vehicles of each type per hour (L, km) using the formula:

Total path = Nj × L,

where, j – for the vehicle type; L – the section length, km; Nj – the number of vehicles of each type per hour.

Calculate the amount of fuel (Qj, l) of different types burned by automobile engines according to the formula:

Qj = Lj × Yj.

Determine the total amount of burned fuel of each type (EQ) and insert the results into Table 4.

Table 4. Fuel Consumption

Calculate the volume of released pollutants in litres under normal conditions for each type of fuel and the total. Insert the results into Table 5.

Table 5. Emission volume

Petrol

Diesel fuel

TOTAL (V), l

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Calculate the mass of released harmful substances (m, g) by the formula: m = V22,4×M ,

where, M – molecular weight.

Calculate the amount of clean air required to dilute the released pollutants to ensure sanitary environmental conditions. Insert the results into Table 6.

Table 6. The amount of air required to dilute pollutants

Write the research protocol.

LABORATORY SESSION

Task 1. Estimate the total air pollution in point A of city C by the level of average annual concentrations of 7 substances:

Carbon monoxide – 5.0 mg/m3, sulphur dioxide – 6.0 mg/m3, suspended solids – 0.5 mg/m3, nitrogen dioxide – 4.0 mg/m3, phosphoric anhydride – 2.4 mg/m3, hydrogen sulphide – 0.016 mg/m3, carbon disulphide – 0.076 mg/m3.

Task 2. Estimate the total air pollution in point A of city C by the level of average annual concentrations of 7 substances:

Carbon monoxide – 7.0 mg/m3, sulphur dioxide – 0.7 mg/m3, suspended solids – 0.9mg/m3, nitrogen dioxide – 4.2 mg/m3, phosphoric anhydride – 2.4 mg/m3, hydrogen sulphide – 0.016 mg/m3, phenol – 0.05 mg/m3.

Task 3. Estimate the total air pollution in point A of city C by the level of average annual concentrations of 7 substances:

Carbon monoxide – 5.0 mg/m3, sulphur dioxide – 1.4 mg/m3, suspended solids – 1.5 mg/m3, nitrogen dioxide – 2.0 mg/m3, phosphoric anhydride – 2.2 mg/m3, hydrogen sulphide – 0.02 mg/m3, formaldehyde – 0.09 mg/m3.

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