Medicine

Hygiene of soil and air

HYGIENE OF SOIL AND AIR.

 METHOD OF HYGIENIC ESTIMATION OF THE SOIL FROM DATA OF SANITARY INSPECTION OF AREA AND BY RESULT OF LABORATORY ANALYSES OF THE TEST.

 CLEANING OF INHABITED PLACES.

METHOD OF DETERMINATION OF CONCENTRATION OF СО2 IN THE AIR AS INDEXES OF ANTROPOGENIC CONTAMINATION OF AIR AND VENTILATION OF APARTMENTS. CONCEPT ABOUT AN AIR CUBE, NECESSARY AND ACTUAL VOLUME AND DIFFERENT TYPES OF VENTILATION, THEIR SCIENTIFIC GROUNDING.

Soil may be defined as the fine earth covering land surfaces that has the important function of serving as a substratum of plain, animal, and human life. Soil acts as a reservoir of nutrients and water and absorbs and oxidises the injurious waste substances that plant growth accumulates in the rhizosphere (i.e.. the root zone). These functions of soil are possible because it contains clay minerals and organic substances (clay and humus form the finer part of soil) that absorb both ions (electrically charged atoms) and water.

                                                       

Average Composition of Soil

Soils are composed of mineral matter, air, water, organic matter, and organisms. There are two general types of soils, mineral soils and organic soils. Mineral soils form from decomposed rocks or sediment derived from rocks. Organic soils form from the accumulation of plant material, usually in water-saturated, anaerobic conditions that retard decomposition. Mineral matter is described as texture and comprises half the volume of mineral soils. The other half of the soil volume is composed of voids or holes. These voids fill with water as the soil soaks up rain or flood waters, then are displaced with air as the water drains away, evaporates, or is absorbed by roots.

Both plants and animals help to create a soil. As they die, organic matter incorporates with the weathered parent material and becomes part of the soil.

  Living animals such as moles, earthworms, bacteria, fungi and nematodes are all busy moving through or digesting food found in the soil. All of these actions mix and enrich the soil. Here is a creature from each major group of soil organisms.

There are many functions provided by soil that are important to human beings. Agriculture and animal husbandry produce more than 90 percent of the human popu­lation's food supply: together with forestry these activities connected with soil produce many oilier materials needed by human beings, such as wood, cellulose, textile fibres, and leather. The utilisation of soil by agriculture, animal husbandry, and forestry is often termed "soil exploita­tion." Soil is necessary for dwellings, highways, airports, and recreation areas, and it also provides road fill and material for water retention structures and fulfills many other essential functions.

 

These horizons collectively are known as a soil profile.

The uppermost is called the organic horizon or O horizon. It consists of detritus, leaf litter and other organic material lying on the surface of the soil. This layer is dark because of the decomposition that is occurring.

  Below is the A horizon or topsoil. Usually it is darker than lower layers, loose and crumbly with varying amounts of organic matter. This is generally the most productive layer of the soil.

  The next layer is the B horizon or subsoil. Subsoils are usually lighter in color, dense and low in organic matter. Most of the materials leached from the A horizon stops in this zone. Still deeper is the C horizon. It is a transition area between soil and parent material. At some point the C horizon will give up to the final horizon, bedrock.    

Basic physical properties and texture of soil

 

Lithosphere (the earth's crust) mineral and organic covering of the Earth, which extends from its surface to magma. It consists of lithosphere itself, which is formed from magma rocks destroyed by physical, physicochemical and chemical processes before beginnings of life on Earth, and soil.

Soil is a surface layer of lithosphere (from few millimeters in mountains and up to 10 kilometers in lowlands), which was formed after beginnings of life on Earth as the result of climate, flora and life (microorganisms and roots of higher plants) influence. Soil consists of the surface or fertile layer (0-25 cm) or humus layer, which is characterized by fertility and which is cultivated at growing plants, and of soil itself.

Soils are very different depending on conditions of their formation, first of all on climate and flora. In Ukraine most common are chernozem (black earth soils) (54.0% of territory), then –– grey forest soils (18.2% of territory) and sod-podsol soils (7.8% of territory).

Average Composition of Soil

 

Basic physical properties of soil:

- texture percentage of soil particles according to their sizes. It is determined by screening through Knopf sieves. There are 7 types (called “numbers”) of such sieves with apertures of different diameters from 0.25 to 10.0 mm (fig. 18.1). Soil texture consists of the following elements: stones and gravel (size > 3 mm); coarse sand (3-1 mm), medium (1-0.25 mm), fine (0.25-0.05 mm); coarse dust (0.05-0.01 mm), medium (0.01-0.005 mm), fine (0.005-0.001 mm); silt (< 0.001 mm). According to texture, soils are classified based on specific weight of physical sand (particles of size > 0.01 mm) and of physical clays (particles of size < 0.01 mm).  (Appendix 3);

- porositytotal volume of pores in the unit of soil volume, which is expressed in percents. The bigger is the size of some elements of soil tissue, i.e. its granularity, the bigger is the size of pores in homogeneous soil. The biggest pores are in rocky soil, smaller ones are in sandy soil, very small pores are in clay soil, and the smallest ones – in peat soil. At that total volume of pores, expressed in percents, increases, i.e. soil porosity is as higher as smaller is the size of some elements of soil tissue. Thus, porosity of sandy soil is 40%, and peat soil - 82%;

Fig. Knopf sieves for soil texture analysis

- air permeabilitysoil ability to let air through its thickness. It increases when size of pores is bigger and doesn’t depend on their total volume (porosity);

- water permeabilitysoil ability to absorb surface water and to let it pass through. Permeability consists of two stages: imbibition, when free pores gradually get filled with water till total saturation of soil and filtration, when, in the result of total water saturation of soil, water starts moving in soil pores because of gravity;

- moisture capacity amount of moisture, which soil is capable to retain due to sorptive and capillar powers. The smaller is the size of pores and the bigger is their total volume, i. e. porosity – the bigger is the moisture capacity. The finer is soil texture, the higher is its moisture capacity;

- soil capillaritysoil ability to lift water via capillaries from the bottom layers up. The smaller is the size of soil texture particles - the bigger is soil capillarity, but in such soil water goes up higher and slower.

In soils of light texture (sandy, clay sandy, light loamy) compared to heavy soils (clays, heavy loams) physical sand prevails, pores are of the larger size, porosity isnt high, air and water permeability, filtration capacity are considerable, capillarity and moisture capacity are low. On the one hand, processes of soil bio-decontamination run rather quickly in such soils, on the other hand, migration of chemical substances from soil into ground and surface water reservoirs, ambient air and plants is more considerable.

Properties of soil particle size

 

Sand

Silt

Clay

Porosity

mostly large pores

small pores predominate

small pores predominate

Permeability

rapid

low to moderate

slow

Water holding capacity

limited

medium

very large

Soil particle surface

small

medium

very large

 

Soil consists of biotic (soil microorganisms) and abiotic components. Abiotic components include hard substance of soil (mineral and organic compounds and organomineral complexes), soil moisture and soil air.

60––80% of mineral (non-organic) substances of soil are represented by crystalline silica or quartz. The important place among mineral compounds is occupied by alumina-silicates, i.e. feldspar and mica. Also to alumina-silicates belong secondary clayey minerals, i.e. of montmorilonite group (montmorilonite, notronite, beidelite, saconite, hectorite, stevensite). Their hygienic importance is them being the cause of absorbing capacity and volume of cations absorption (i.e. heavy metals) by soil.

Beside silica and alumina-silicates, almost all elements of Mendeleyevs table appear in mineral compound of soil.

Organic substances of soil are represented both by soil organic (humic acids, fulvic acids etc.) compounds, which are created by soil microorganisms and which are called humus, and by strange for soil organic substances, which came into the soil from outside in the result of natural processes and technogenic (anthropogenic) pollution.

Soil moisture can be both in solid and liquid forms, and in the form of vapour. From hygienic point of view of the most interesting is liquid moisture, which can be in forms of: 1) hygroscopic water, which is condensed on the surface of the soil particles; 2) membranous water, which remains on the surface of soil particles; 3) capillary water, which is kept by capillary forces in thin pores of soil; 4) gravity free water, which is influenced by gravity or hydraulic head and fills in soil big pores.

Soil air is a mixture of gases and vapour, which fills in soil pores. According to its composition it differs from atmosphere air and constantly interacts with it by diffusion and concentration gradient. Soil air and water oppose to each other in respect of space in pores. Natural compound of soil air is controlled by oxygen utilization rate and carbon dioxide generation as the result of microbiological processes of mineralization of organic substances. With growth of depth content of carbon dioxide in soil air increases and oxygen content - decreases.

Hygienic significance of soil

Soil is:

- the medium, where processes of transformation and soil energy accumulation take place;

- leading member of turnover in nature, the medium, in which different complicated processes of destruction and synthesis of organic substances take place continuously;

- main element of biosphere, where processes of migration, transformation and metabolism of all chemical substances both of natural and anthropogenic (technogenic) origin take place. Migration takes place both in short (soil –– plant –– soil, soil –– water –– soil, soil –– air –– soil) and long (soil –– plant –– animal –– soil, soil –– water –– plant –– soil, soil –– water –– plant –– animal –– soil, soil –– air –– water –– plant –– animal –– soil etc.) migration chains;

- forms the chemical structure of foodstuffs of vegetable and animal origin;

- plays an important role in formation of water quality of surface and ground sources of domestic and drinking water-supply;

- affects qualitative structure of contemporary atmosphere;

- of endemic importance – anomalous natural chemical structure of soil in endemic provinces is a reason of rise and local spreading of endemic diseases (geochemical endemic diseases): endemic fluorosis and caries, endemic goiter, foot-and-mouth disease (FMD), molybdenum gout, endemic osteoarthritis or Kashin-Beck disease, endemic cardiomyopathy (Keshan's disease), selenosis, boric enteritis, endemic nephropathy etc.;

- of epidemic importanceit can be a transmission factor of pathogens of infection diseases and invasions to people: enteric infections of bacterial (typhoid, paratyphoids А and В, bacillary dysentery, cholera, coli-entheritis), viral (virus A hepatitis, enterovirus infections: poliomyelitis, Coxsackie virus infection, ЕСНО) and protozoa ethiology (amebiasis, lambliosis); zooanthroponosis (types of leptospirosis: infectious jaundice or VasylyevVail disease, anicteric leptospirosis, brucellosis, tularemia, anthrax); mycobacteria of tuberculosis; spore-forming clostridia – pathogens of tetanus, gas gangrene, botulism; geohelminthosisascaridiasis, trichocephalosis, ankylostomiasis.

- the place for liquid and soil domestic and industrial waste disposal due to natural purification processes (soil sanitary significance). Soil natural purification is characterized by presence of saprophytic decomposers, nitrifying and nitrofying bacteria, elemental organisms, larvae, worms, fungi, viruses, coliphages and by its physical-and-chemical properties. It consists in soil capability to transform organic compounds into mineral substances good for plantsassimilation:  carbohydrates – into water and carbon dioxide; fats– into glycerin and fatty acids and thenalso into water and carbon dioxide; proteins – into amino acids with ammonia and ammonia salts evolvement and their further oxidation to nitrites and nitrates; protein sulfur – into hydrogen sulfide etc.

Methods of land parcel sanitary inspection and soil sampling

Sanitary inspection of the land parcel includes:

- definition of ground assignment (territory of a hospital, preschool institutions, schools, industrial enterprises, objects of waste disposal of domestic, industrial, construction origin, etc);

- visual inspection of the parcel, determination of character and location of sources of soil pollution (distance), relief, drain direction of precipitation waters, flow direction of ground waters;

- determination of soil texture (sand , clay sand, loamy soil, chernozem);

- determination of points for soil sampling for analysis: places near the source of pollution and near test area of known clean soil (at a distance of this source).

Samples are taken byenvelope” technique on rectangular or square areas of 10×20 meters or more. In each of five sampling points of the envelope1 kg of soil is taken from the depth of 20 cm for samples. An average sample of 1 kg mass is prepared from taken samples.

 

Each taken sample is accompanied by a covering letter, which includes information about place, address and assignment of the parcel, soil type, relief, ditch level of subterranean waters, goal and volume of the analysis, inspection results received at the place, date and time of sampling, weather of previous 4-5 days, who took a sample, his signature. Samples are packed into closed glassware and polyethylene bags.

When

Soil samples may be taken at any time during the year when soil conditions permit.  The soil should not be too wet or muddy as it will dry as hard as a rock and may be difficult to mix.

 

Where

If the area is fairly level and the soil appears to be uniform, collect 5 samples and mix together to form a composite sample.

If your lawn or garden has large areas which differ in fertility, take one composite sample from each area.   For example, you may want to sample the back veggie garden (A composite sample from 5 sub-samples labeled A) and from the front lawn ( a composite of 5 sub-samples labeled B).(see diagram below).  If you are fertilizing these areas differently it makes sense to take two different samples for soil testing because.

How?

It is best to use a soil sampler which samples uniformly to the depth you want.  You can do this with a garden trowel if you are careful  to get a uniform about in each sample to the depth of 15 cm or 6 inches.



 

Gather your soil sample from the root zone rather than from the surface. You'll need at least one cup of soil.

Criteria of soil sanitary state

Group of indices

Indices

Sanitary-and-physical

Texture of soil, filtration coefficient, air and water permeability, capillarity, moisture capacity, total hygroscopic moisture

Physical-and-chemical

Active reaction (рН), absorption capacity, total absorbed bases

Chemical safety criteria:

- chemical agents of natural origin

Background content of total and movable forms of macro- and microelements of non-contaminated soil

- chemical agents of anthropogenic origin (soil pollution indices, ЕCS)

Amount of pesticide residues, total content of heavy metals and arsenic, content of movable forms of heavy metals, oil and oil products’ content, content of sulphides, content of carcinogens (benzpyrene) etc.

Epidemic safety criteria:

- sanitary-chemical

Total organic nitrogen, Khlebnikoff’s sanitary number, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, organic carbon, chlorides, soil oxidation

- sanitary-microbiological

Total number of soil microorganisms, , microbial number, titer of bacteria of colibacillus group (coli-titer), titer of anaerobes (perfingens-titer), pathogenic bacteria and viruses

- sanitary-helminthological

Number of eggs of helminthes

- sanitary-enthomological

Number of larvae and chrysalides of flies

Radiation safety indices

Soil activity

Soil natural purification indices

Titer and index of thermophile bacteria

 

All indices are divided into direct (allow to assess the level of soil contamination and level of danger for population health directly from the results of laboratory analysis of taken samples and indirect (allow to draw a conclusion of the existence of soil contamination, its prescription and duration by comparison of the results of soil laboratory analysis with test clean soil of the same type, which was taken as a sample from non-contaminated areas).

Sanitary number of Khlebnikoffis a ratio of humus nitrogen (pure soil organic substance) to total organic nitrogen (consists of humus nitrogen and nitrogen of strange for soil organic substances that contaminate it). If soil is pure, sanitary number of Khlebnikoff equals to 0.98-1.

Soil coli-titeris a minimal amount of soil in grammas, in which one bacteria of colibacillus group is found.

Soil anaerobe titer (perfingens-titer) is a minimal amount of wastes in grammas, in which an anaerobic clostridia is found.

Soil microbial numberis a number of microorganisms in one gram of soil that grew up on 1.5% beef-extract agar at temperature 370С during 24 hours.

 

Soil classification according to texture (according to N.А. Kachinskiy)           

Names of soils according to texture

Content of particles, %

Clay particles of a diameter smaller than 0.01 mm

Sand particles of a diameter larger than 0.01 mm

Heavy clay soils

larger than 80

smaller than 20

Clay soils

from 80 to 50

from 20 to 50

Heavy loamy soil

from 50 to 40

from 50 to 60

Medium loamy soil

from 40 to 30

from 60 to 70

Light loamy soil

from 30 to 20

from 70 to 80

Clay sands

from 20 to 10

from 80 to 90

Sandy

from 10 to 5

from 90 to 95

Light sandy

smaller than 5

larger than 95

Filtration capability of soils of different texture

 

Filtration capability

Time of absorption, s*

Type of soil

Large

<18

coarse-grained – and medium size - grained sand

Medium

18––30

fine-grained sand,

light clay sand

Small, but sufficient for active realization of processes of organic decontaminations

30––180

Light adobe

Small and insufficient for realization of processes of organic decontaminations

>180

Heavy and medium clay sands and loamy soil, clays

 

 

 

Technique of hygienic assessment of sanitary state of soil

When drawing a report on hygienic assessment of sanitary condition of soil it is reasonable to use a scheme (algorithm) that provides for the following 6 stages:

І goal and task are determined. Thus it is necessary to state a hygienic value of sanitary condition of natural soil at the time of the assignment of the parcel for new settlement construction. During the regular sanitary inspection it is necessary to assess the sanitary condition of artificially created soil on the ground areas for residential and public building, playgrounds for children and sport grounds. When the epidemic situation is unfavorable, it is necessary to find out if soil is a factor in spreading pathogenic microorganisms. Sometimes, when investigating cases of acute and chronic poisonings it’s necessary to determine the level of soil contamination by toxic chemical substances (pesticides, heavy metals etc.). Sanitary condition of soil may be studied in order to assess the efficiency of sanitary purification of the settlement territory, during the regular sanitary inspection of sewage disposal plant and facilities of utilization and extermination of SDW in order of assessment of their work efficiency.

II – according to set tasks a required extent of examinations is set. Thus, during the hygienic assessment of natural soil of the ground areas assigned for new settlement construction, complete sanitary analysis of every index of sanitary condition is required. During the hygienic assessment of artificially created soil of settlements, in case of favorable epidemic situation, it is reasonable to carry out examinations by sanitary analysis reduced scheme: determination of total and hygroscopic moisture, Khlebnikoff’s sanitary number, chlorides, soil oxidation, microbial number, titer of coli-group bacteria, anaerobe titer, number of eggs of helminthes, number of larvae and chrysalides of flies. In case of unfavorable epidemic situation it is important to include tests on presence of pathogenic bacteria and viruses into reduced sanitary analysis. When investigating cases of acute and chronic poisonings for the assessment of the level of soil contamination by chemical poisonous substances it is sufficient to determine texture of soil, total and hygroscopic moisture and content of hazardous substances: pesticides, heavy metals, arsenic etc.

III – completeness of presented materials and availability of sanitary examination data are controlled, soil sampling schemes, methods of their preliminary analysis, time constraints of analysis, soil samples’ keeping are assessed, availability of soil laboratory analysis results in accordance to the required research program are controlled.

IV – sanitary examination results are analyzed: а) sanitary-topographical characteristic of the area; b) sanitary-technical characteristic of the objects that influence condition of the area; c) sanitary-epidemic situation. Preliminary conclusion concerning grounds for suspicion that soil can be contaminated by exogenic chemical substances or being a factor of spreading infections is drawn.

V – laboratory results of soil analysis are assessed according to all data, that are required by examination program. According to indirect indices based on comparing the examined and test (“pure”) soil one, conclusion about the fact of existence, prescription and durability of contamination is drawn. According to direct indices, based on sanitary assessment of the condition of soil (Appendices 4, 5), level of soil contamination and stage of its danger for the population health is assessed.

VI – general conclusion about sanitary condition of soil, stage of its contamination and danger for the population health is drawn, future soil pollution effect on population health depending on its levels is forecasted (Appendix 6), preventive measures of  further deterioration of sanitary state of soil and ways of its improvement are offered.

SOIL POLLUTION

Soil pollution is usually a consequence of insanitary habits, various agricultural practices, and incorrect methods of disposal of solid and liquid wastes, but can also result from fallout from atmospheric pollution. It is closely linked with the ultimate fate of those substances that are unlikely to undergo the natural recycling processes to which putrescible matter is subject. In industrialized countries, soil pollution is associated mainly with:

(1) The use of chemicals, such as fertilizers and growth-regulating agents, in agriculture;

(2) the dumping on land of large masses of waste materials from the mining of coal and minerals and the smelting of metals.   Toxic or harmful substances can be leached out of such materials and enter the soil;

(3)          The dumping on land of domestic refuse and solids resulting from the treatment of sewage and industrial wastes.

(4)          The soil is thus becoming increasingly polluted with chemicals, including heavy metals and products of the petroleum industry, which can reach the food chain, surface water, or ground water, and ultimately be ingested by man.

 

In many countries of the world, and particularly in the developing ones, soil pollution with pathogenic microorganisms is still of major importance. In such countries, intestinal parasites constitute the most important soil pollution problem, as a result both of the improper disposal of human excreta, waste water, and solid wastes, and of incorrect agricultural practices. Thus it is estimated that about one-third of the world's popula­tion is infected by hookworm, while one out of every four people in the world may be infected with Ascaris lumbricoides.

Soil Pollution by Biological Disease Agents

Biological agents that can pollute the soil and cause disease in man can be divided into three groups:

(1) pathogenic organisms excreted by man and transmitted to man by direct contact with contaminated soil or by the consumption of fruit or vegetables grown in contaminated soil (man-soil-man);

(2)   pathogenic organisms of animals, transmitted to man by direct contact with soil contaminated by the wastes of infected animals (animal-soil-man); and

(3)   pathogenic organisms found naturally in soil and transmitted to man by contact with contaminated soil (soil-man).

Man-soil-man

Enteric bacteria and protozoa

Enteric bacteria and protozoa can contaminate the soil as a result of: (a) insanitary excreta disposal practices; or (b) the use of night soil or sewage sludge as a fertilizer, or the direct irrigation of agricultural crops with sewage. Soil and crops can become contaminated with the bacterial agents of cholera, salmonellosis, bacillary dysentery (shigellosis) and typhoid and paratyphoid fever, or with the protozoan agent of amoebiasis. However, these diseases are most often water-borne, and transmitted by direct person-to-person contact, or by the contamination of food. Flies that breed in, or come into contact with, faecal-contaminated soil can serve as mechanical carriers of disease organisms.

Parasitic worms (helminthes)

Soil-transmitted parasitic worms or geo-helminthes are characterized by the fact that their eggs or larvae become infective after a period of incubation in the soil.

Animal-soil-man

In a number of zoonoses (diseases of animals transmissible to man), the soil may play a major part in transmitting the infective agent from animal to man.

Leptospirosis

This disease affects both animals and man in all parts of the world. The epidemiology of the disease follows a characteristic pattern similar to that of other zoonoses, namely animal to animal, and animal to man. In some areas, sheep, goats, and horses become infected. Rodent carriers include rats, mice, and voles. The dispersion of leptospires is associated with specific environmental condi­tions, particularly those that bring animal carriers, water, mud, and man together. Animal carriers often excrete a profusion of leptospires—up to 100 million per ml—in the urine. If this is excreted into water or mud that is neutral or slightly alkaline, the leptospires may survive for weeks. Susceptible animals and man entering this environment are exposed to the agent and may develop infection varying from an inapparent reaction to an acute fulminating fatal disease. Leptospires usually enter the body through the mucous membranes or broken or macerated skin. Agricultural workers in irrigated fields, and in rice and cane fields in particular, often become infected.

Anthrax

The number of reported cases of anthrax in man is relatively small compared with the figures for other zoonoses; nevertheless, anthrax is still of importance both as a human disease and because of its economic impact on animal husbandry. The spores of Bacillus anthracis are very resistant to chemical and environmental influences and can survive for years in certain soils as well as in animal products, such as hides, hair, and wool. When anthrax infections in livestock become established in a district, a relatively permanent enzootic focus of infection is created because of the long period for which the spores can remain viable in the soil.

Other diseases

Among other diseases that follow the sequence animal-soil-man, mention should be made of the following: visceral larva migrans, due mainly to Toxocara canis, listeriosis, Clostridium perfringens infections, lymphocytic choriomeningitis, South American types of haemorrhagic fever, tuberculosis, salmonellosis, and tularaemia. Although most of these diseases and infections are transmitted predominantly by direct animal-man contact, or through the contamination of food by animal droppings and wastes, soil pollution may also play an important part.

Soil-man

Mycoses

Fungi and actinomycetes that grow normally as saprophytes in soil or vegetation cause most of the serious subcutaneous, deep-seated and systemic mycoses. Under certain circumstances, however, they become pathogenic and invade specific tissues or entire systems.

Tetanus

Tetanus is an acute disease of man induced by the toxin of the tetanus bacillus growing anaerobically at the site of an injury. The organism has a world-wide distribution, though cases of the disease are comparatively infrequent today. The infectious agent, Clostridium tetani, is excreted by infected animals, especially horses. The imme­diate source of infection may be soil, dust, or animal and human faeces.

Botulism

This is a frequently fatal type of poisoning caused by bacterial toxins produced by Clostridium botulinum. The reservoir of the organism is soil and the intestinal tract of animals. The toxin is formed by the anaerobic growth of spores in food, which is the immediate source of poisoning. The disease is usually transmitted by the ingestion, without previous cooking, of food from jars or cans imperfectly sterilized during canning, the canned or preserved food having been infected with soil contaminated by Cl. Botulinum.

Soil Pollution and Solid Wastes Disposal Urban areas

The land serves as a major repository for the solid wastes of urban and industrial areas. Solid wastes disposal in metropolitan areas has a number of public health implications.

The problem of greatest concern stems from the fact that, with increasing urbanization and the consequent increase in the area occupied by buildings, the land available for depositing wastes is correspondingly reduced.

In highly industrialized countries, even the solid wastes from agriculture can become a problem, particularly when livestock and poultry wastes near urban centres become a breeding ground for flies and cause a serious odour nuisance on decomposition.

Production per head of solid wastes varies considerably from country to country, but with rising living standards the amount of refuse produced is everywhere on the increase. In the USA and some European countries this increase is estimated at about 3 % per year by volume, and 2 % per year by weight.

The problems of land pollution by wastes differ in a number of import­ant respects from those of water or air pollution, since the polluting material remains in place for relatively long periods of time unless removed, burned, washed away, or otherwise destroyed.

In many of the more developed countries, aesthetic considerations have become important in wastes disposal and there is less readiness to accept unsightly, open refuse dumps and junk heaps as an inevitable blot on the landscape. Insects and rodents, which breed in such dumps, and odours from decomposing organic matter or from slow smouldering fires, can cause severe nuisance and public health problems.

With the increasing utilization of land for urban development, pressure to dispose of solid wastes by methods other than land disposal has led to new pollution problems. Improper incineration can lead to severe air pollution, while discharge into water leads to overloading of treatment facilities and to increased pollution in already heavily burdened watercourses.

Agricultural land pollution

In the past, nutrient materials in the agricultural economy followed a clearly defined cycle: from the land to plants, from plants to animals, and then back to the land again. In some of the more highly industrialized countries, the use of chemical fertilizers has short-circuited this cycle, and many agricultural areas now have large surpluses of plant and animal wastes that, unless properly disposed of, can cause soil pollution. The problem becomes particularly severe where urban areas border on agri­cultural land. In these fringe areas, agricultural solid wastes may ulti­mately have to be handled in the same way as urban wastes.

As agriculture becomes more intensive, so that increasing quantities of synthetic materials, such as pesticides, nutrients, and control agents, are used, chemical soil pollution coupled with increasing amounts of excess organic waste materials leads ultimately to severe land pollution problems in agricultural areas.

Contamination of the Soil by Toxic Chemicals

Agricultural chemicals

Fertilizers are intended to fortify the soil for the raising of crops, but incidentally may contaminate the soil with their impurities. Irrigation of farmlands and orchards may do this if the source of water is polluted by industrial wastes that contain synthetic organic chemicals. During the last few decades, herbicides, insecticides, fungicides, soil conditioners, and fumigants have produced intentional alterations of agricultural, horticul­tural, and silvicultural soils. The chemicals used may pollute the soil water.

Solid wastes from industry

Leach ate from industrial solid wastes may contain poisonous chemicals in solution; these may be concentrated in nature by various organisms in the human food chain.

A recent study has shown that the disposal of industrial solid wastes constitutes a major source of land pollution by toxic chemicals. It has been estimated that some 50 % or more of the raw materials used by industry ultimately become waste products, and that about 15 % can be considered deleterious or toxic. In the United Kingdom, close to one million tons of materials classified as flammable, acid, caustic, or indisputably toxic are dumped annually by industry. This amounts to about 20 kg per person per year. A major portion of these wastes is dumped on the land either by private contractors or by arrangement with local authorities. Some wastes are dumped at sea or incinerated.

These wastes have, in certain instances, given rise to severe problems of soil pollution, either by poisoning the soil or crops, or by eventual entry into ground-water and surface-water sources.

Radioactive materials

Radioactive materials can reach the soil and accumulate there, either from atmospheric fallout from nuclear explosions, or from the release of liquid or solid radioactive wastes produced by industrial or research establishments. The two most important radionuclides with long half-lives produced by nuclear fission are '"Sr (half-life 28 years) and 137Cs (half-life 30 years). Fallout of relatively recent origin and discharges from nuclear reactors also contain a number of other radionuclides of importance from the ecological point of view, e.g., 131I, u°Ba + 140La, 106Ru + 106Rh, 144Ce + 144Pr, etc.

Levels of radiation from fission products deposited in the soil by fallout in the northern hemisphere are about 10-30 % of those due to natural radioactive substances in the soil. Many authorities feel that there is very little evidence to date to show that this increase in radiation levels could affect soil fauna or their predators, but increased radioactive fallout could in time result in levels of soil contamination high enough to cause concern.

Pollution of the land by the biological agents of disease remains one of the major causes of debilitating infections in the rural and semi-rural areas inhabited by the majority of the world's population. Land pollution by toxic chemicals from agriculture and industry, leading to the contamina­tion of soil, food, and water, may prove to be a significant hazard to health in the more industrialized areas of the world. The problems arising from the dumping on land of the ever-increasing amounts of domestic and indus­trial solid wastes will become more acute as world population and the degree of urbanization increase.

Mechanic content of soil and it’s hygienic meaning

Sanitary condition of soil depends greatly on its structure.

  Soil consists of dense, liquid, gas and alive components. Soil solution is water with solved gases, mineral and organic compounds. The types of soil liquid component are film, capillary and gravitation water. Dense component consists of mineral compounds and humus – biogenic heavy-molecular dark colored soil (humine acids, humane and ulmine). Gas components ratio depends on amount of pores and the sanitary condition of soil. Soil microflore, plants and animals inhabiting depends on climatic and geologic conditions.

  Mechanic analysis data make available the following divisions of soils: stony, gravel, cartilage, sandy (>80% sand and <10% of clay); sandy loam soil (50-80% of clay), lesser loamy soil (30-50% of clay), loamy soils (50-80% of clay), clay soils (>80% of clay), lime soils (>80% of clay), chalk soils, lessic soils (mixture of small sand particles with lime clay), black earth (>20% of humus), turf soils etc.

In pity soil the main component is organic substances of soil. The soil, which content the big-size of grain (sand, subs and), have a big pores. At the same time, the size of that pores is not very big: it is near 25-40 % from general volume of soil. The soil, which content the big size pores, have a good penetration for water and air, that is why it’s dry and content much air in it.The soil, which have the small size of grain ( it’s clay and peat) content the big number of small pores; the clay have 45-50% of pores and peat have – to 84% once. In consequence, the soil of small size of pores, which have the grain of small sizehave bigger dampness and bad penetration for water and air.

According to cleanness the soil is divided on

 

Coli-tytre

Perfringens-tytre

Number of helminthes eggs in 1 kg

Sanitary index*

Flies chrysalis in 0.25 m2

Clean

>1.0

>0.1

0

0.98-1.0

0

Low pollution

1.0-0.01

0.1-0.001

10

0.85-0.98

1-9

Polluted

0.01-0.001

0.001-0.0001

10-100

0.7-0.85

10-25

Heavily polluted

<0.001

<0.0001

>100

<0.7

>25

Methods of sanitary analysis of soil:

        sanitary entomological

        sanitary-helmontologic analysis

        sanitary-biological

        sanitary-chemical

        sanitary-physical

        sanitary-radiological

 

 There are the indices of soil disperse capacity.

  The disperse properties of soil determine its air content: filtration capacity, water content, capillarity, hygroscopic properties, evaporation capacity.

  The epidemiological importance of soil depends on its capacity of infections, invasions and infestations spreading.

  Ecologic and epidemiological analysis of soil should include the evaluation of their biogeocenoses, the following ways of toxic, radioactive and biological agents transmission are possible:

  Sanitary-entomological studies determine a number of winged flies, maggots, pre-chrysalis and chrysalis.

  Sanitary-helminthological analysis defines quantity of helminthes eggs and larvae.

Cleaning of the soil

Self-regeneration of soil results in destruction of organic compounds to the level of mineral salts: nitrites, sulfates, carbonates which can be consumed by plants. Pathogenic microflora perishes suppressed by the antagonistic soil microbes associations and the soil chemical aggression. Helminthes eggs are being destroyed by UV sun radiation, parching etc. Fitoncides produced by some plants are able to kill pathogenic microbes.

  Nitrification is the basic process of soil regeneration. It’s the conversion process of restored organic nitrogen compounds into oxydated inorganic ones. There are heterotrophic and autotrophic nitrification ways. Heterotrophic nitrification is performed by living organisms (fungi included), which affect both organic and inorganic niter compounds Nitrification is the basic natural way of nitrates conversion. The optimum temperature range for nitrificating bacteria is 25-37°C, the process fails under 3°C and over 50°C. Most nitrificators are aerobic, their growth and development claims good soil aeration. The most active nitrification processes run in porous soils with particles sized 2-10 mm (sandy soils, sandy loam, black earth). Soil cultivation and ploughing helps aeration. Soil humidity under 25-30% suppressed nitrification.

NITROGEN CYCLE

  The most interesting of all vital phenomenon taking place in soil is disposal and utilization of organic matter. This is illustrated by nitrogen cycle.

 STEPS:       

Organic proteins burried in soil are decomposed by putrefactive bacteria. Result is formation of amino compounds & then these compounds are broken down into NH3 & CO2.

 CO2 escapes from these compounds in atmosphere.

 Ammonia in soil is converted into ammonium chloride or ammonium carbonate.     In soil, ammonia is oxidized by action of nitrifying bacteria first into nitrates and then in nitrites.

 Nitrites are taken up by plants, which are in turn taken up by animals. If nitrites are found in soil water, it indicates pollution and signifies active bacterial action and presence of organic matter. Nitrates alone are index of past pollution only.

            Significance of Nitrogen Cycle

.Purification of atmosphere

Organic decomposition

3.     Fertilization power of soil increases

Nitrate (NO3) containing water is preferred. It is further purified.

 

Сleaning  of populated places

Disposal of Solid Wastes

Solid wastes include domestic refuse and other discarded solid materials, such as those from commercial, industrial, and agricultural operations; they contain increasing amounts of paper, cardboard, plastics, glass, and other packaging materials, but decreasing amounts of ash. The amounts produced are increasing throughout the world; urban wastes alone amount to about 600 kg per capita annually, and for industrialized countries pro­bably at least 700 kg per capita, with an annual increase of 1-2 %. As the density of domestic waste is decreasing, annual per capita volumes of up to 5 cubic metres are common. These figures do not include the additional solid wastes produced by agricultural and industrial operations, and as a by­product of sewage treatment.

The insanitary collection and disposal of solid wastes creates serious health hazards, e.g., by encouraging the breeding of flies, mosquitos, rodents, and other vectors of disease. It may also contribute to water pollution, air pollution, and soil pollution. It has adverse effects on land values, constitutes a public nuisance, and thus contributes to the deteriora­tion of the environment.

The appropriate intervention and control measures are the rapid removal of refuse from premises by an efficient collection system and the proper processing of refuse before final disposal or re-use.

A refuse disposal system includes essentially: (1) the transportation system, using automotive vehicles, railway transport, pneumatic transport in pipelines under vacuum, and liquid transport in trunk sewers. Transfer stations for changing from one method of transport to another (e.g., truck hauling to railway hauling) are also necessary; (2) facilities for the pro­cessing of solid wastes, possibly using one or more of the following tech­niques: segregation of refuse components, incineration, composting, pulverization, compaction, and grinding; and (3) facilities for the sanitary discharge of residues into the environment, e.g., sanitary landfill, controlled discharge into bodies of water, and discharge into the air of combustion gases and particulate matter.

There are numerous alternatives for the handling and disposal of solid wastes. In selecting the best, consideration must first be given to the protection of the health of the community and the prevention of public nuisances. The salvaging of constituents of refuse, such as paper, glass, steel, etc., for re-use by industry must also be considered.

Methods of collection and disposal

The rapid increase in the production of wastes is causing storage, collection, and transportation difficulties, as well as problems of treatment and final disposal.

Storage is largely a local problem; it becomes acute in housing develop­ments and apartment blocks where adequate provision for storage has not been made. Collection and transportation have recently been intensively studied in various parts of the world, using operations research techniques, with a view to improving efficiency and lowering costs. Unconventional systems, such as hydraulic or pneumatic transport in pipes, are being developed, especially for new towns and residential areas. These developments, which are very promising, will eventually reduce collection costs and minimize human contact with solid wastes.

Collection and transportation costs vary widely, depending on popula­tion density, route planning, the location of disposal sites, labour costs, etc. Careful planning of routes and of pick-up procedures should make significant savings possible.

Substantial savings in handling costs can be achieved by conservation (reducing the volume of waste), land disposal and on-site treatment, both anaerobically or through the use of oxidation ponds or aeration ditches.

The most difficult problem, however, remains that of disposal. Because of the potential nuisance involved, the choice of disposal sites is often a source of serious" controversy. Ideally, the site should be selected or the basis of regional studies. The disposal methods of choice are incineration, sanitary landfill, and composting. Unfortunately, indiscriminate dumping is still practised, both on land and on sea. Incinerator design is improving as combustion efficiency improves and greater control is obtained over gaseous emissions; even after incineration, however, a sizeable volume of ash remains.

Composting, although it has widespread popular appeal, has become increasingly uneconomical as a means of disposal, both because of the changing nature of refuse and the difficulty in disposing of the compost itself.

Sanitary landfill is everywhere the most popular method of disposal. While it requires the use of relatively large areas, it can be used effectively for land reclamation purposes; when properly managed it can be inoffensive, and avoid both air pollution and, to a large extent, leaching and resulting water pollution. A modification of the process is being developed in certain areas; refuse is hauled relatively long distances by rail, and disposal is combined with strip-mining operations.

Other processes, still at the experimental stage, include pulverization into a dense, homogeneous, and relatively inoffensive material. This process reduces transport costs and land area requirements for sanitary landfill. Investigations are also being carried out on the high-pressure compaction of refuse into blocks of high density. These blocks could be used as a filling material and for the reclamation of derelict land.

The importance of recycling in refuse disposal has been emphasized by the conservation-minded. It is almost always a marginal operation from an economic point of view, although aluminium, glass, iron, paper, and other materials can be reclaimed.

Sanitary purification of settlements

 

It is a set of measures that provide for the fulfillment of hygienic requirements during arrangement and exploitation of equipment and facilities that are meant for collecting, temporary keeping, transportation, destruction and utilization of solid and liquid domestic and industrial waste.

Waste these are remains of substances and articles that have been created as the result of domestic, economic and industrial human activity, and cannot be used at the scene of their creation so that their accumulation and keeping make the sanitary condition of the environment worse. They are divided into liquid: 1) sewage from cesspool toilets; 2) slops (from cooking and dish and floor washing etc.) and 3) waste waters: domestic, industrial, runoffs, municipal waste water and solid: 1) garbage (domestic refuse); 2) rubbish (kitchen waste products); 3) waste from patient care and prophylaxis institutions (including specific ones –– used dressing, used disposable autotransfusers and syringes, remains of medicines, remains of organs and tissues after surgical operations, dead bodies of laboratory animals etc.); 4) institutional waste (schools, preschool institutions, high schools and academies, offices, etc; 5) waste of public catering establishments; 6) waste of animal origin (dead bodies of animals, pus, forfeit foodstuff); 7) waste of commercial facilities; 8) industrial waste; 9) slags from boiler houses; 10) construction waste, urban soil; 11) street sweepings.

 

There are three different systems of waste disposal: flushing” removal, “pick-up” removal and combined removal.

Flushing system is used in the settlements, which are provided with sewerage (pipe) system through which liquid and partially fine solid waste float to waste disposal plants; the rest of solid waste is removed by special motor transport.

Pick-up system is used in the settlements without sewerage systems. At that both liquid and solid domestic waste (SDW) is removed to areas of disposal and utilization by special motor transport. Such method of disposal of solid waste is called purification, and of liquid wastes sanitation.

Combined system is used in the settlements that are partially provided with sewerage system. According to combined system liquid waste from the part of settlement, provided with sewerage system, is removed through this system, and from the part of the settlement where there is no sewerage system – with the help of cesspoolage transport. All solid waste is removed by sanitary purification transport.

Sanitary purification of settlement must be systematic (to be performed according to agreed plan and schedule), regular (waste removal in warm seasondaily, in cold seasononce per 1-3 days), utility (to be performed by utilities and community services, or trusts) and to be independent from wishes of some officials or institutions. It consists of three stages: I –– collection and temporary keeping of solid domestic waste; II –– removal; III –– disposal and treatment.

Collection, removal (transportation) of solid domestic wastes.

In case of neighbourhood-based system SDW is collected into special dustbins that are located at specially arranged plots on the territory near the houses and later on, according to the schedule, it is removed by special motor transport to the place of disposal. In case of door-to-door-based system waste is collected in apartments. At the certain time inhabitants take it out to a dust-cart. There are two different methods used in case of neighbourhood-based system - method of "fixed" container (waste from dustbins is emptied into dust-carts and dustbins are placed back) and method of "disposeable" container (dustbins together with solid waste are removed by dust-carts to waste disposal places, while empty and clean dustbins are left instead of the used ones).

For garbage and other solid waste removal special motor carsdust-cartsare used. For method of "fixed" container they use dust-carts 93/М, 53/М, КО-404, КО-413 etc., for method of " disposeable " container dust-carts М-30. They are mounted on the chassis of the trucks GAZ-93а, GAZ -53, MAZ -500А.

Solid domestic waste disposal. All methods of SDW disposal have to meet the following basic hygienic requirements:

- they must provide reliable disposal, transformation of waste into harmless from epidemic and sanitary point of view substrate. From epidemic point of view solid domestic waste is very dangerous: when titer is 10-6-10-7, titer of anaerobes is - 10-5-10-6, microbial number achieves tens and hundreds of billions, contains pathogenic and conditionally pathogenic bacteria, viruses, eggs of helminthes. Especially dangerous is waste from patient care and prophylaxis institutions, which is approximately 10-100 times more contaminated by microorganisms than domestic waste;

- quicknessideal method is the one that makes possible effective waste disposal during the same period of time in which the waste is formed;

- they must prevent laying eggs and larvae and chrysalides development of flies (Musca domestica) both in waste during its disposal and in substrate, which was obtained in the result of the disposal;

- they must prevent access of rodents during waste disposal and to convert waste into unfavourable for their life and development substrate;

- they must prevent air pollution by volatile products of demolition of organic substances (SDW contain up to 80 % of organic substances, 20-30 % of which easily rot in summer and at the same time evolve stinking gases: hydrogen sulphide, indole, skatole and mercaptans);

- in the process of waste disposal neither surface nor ground waters may be polluted;

- they must provide the best and safe for peoples health use of SDW properties, because they contain up to 6% of utilizable waste; by its burn one can receive heat energy, by biothermal treatment –– organic fertilizers, and food waste may be used for cattle feeding.

According to the final result methods of SDW disposal are divided into: utilizing (waste processing into organic fertilizers, biological fuel, separation of secondary raw materials, e. g. scrap metal, for industry, use as a power-plant fuel) and liquidation (land disposal, sea disposal, incineration without help of heat). According to technological principle methods of disposal are divided into: 1) biothermal (plough-lands, improved dumps, waste store grounds, waste composting fields, bio-chambers, plants for biothermal treatment; in rural area in farms –– compost heaps, hotbeds); 2) thermal (combustion plants without or with utilization of heat energy, which is created in the result of this process; pyrolysis leading to formation of fuel gas and similar to mineral oil - lubricating oil); 3) chemical (hydrolysis); 4) mechanical (waste separation with further utilization,  pressing into construction blocks); 5) combined.

Most widely used are biothermal methods. They are based on the complicated processes of soil natural organic purification from pollutants that may be represented in diagram:

 

Organic

substances

(proteins, fats, carbohydrates)

+

Microorganisms

(bacteria, fungi, actinomycete, algae, protozoa)

+

Oxygen of the air

 

 

 

 

 

 

Humus

(newly synthesized by microorganisms  organic matter)

+

Carbonates, phosphates, nitrates, sulphtes

+

Energy

 

 

Biothermal disposal makes it possible to solve two tasks: 1) to decompose complex organic matters of waste and its metabolism products (urea, uric acid etc.) into simpler compounds in order to synthesize by special microorganisms in presence of ambient air a new, stable, safe from sanitary point of view substance, called humus; 2) to destroy vegetative forms of pathogen and conditionally pathogenic bacteria, viruses, protozoa, eggs of helminthes, eggs and larvae of flies, seeds of weeds.

Efficiency of biothermal method of waste disposal depends on:

- aeration of waste (it is necessary to fan 25 air volumes for 1 volume of SDW);

- waste moisture (if moisture < 30 %, SDW must be moistened artificially; if > 70 %, it is necessary to install  devices for its lessening);

- content of organic substances in waste that are capable to rot easily (mustn’t be  < 30 %, in the ration of carbon to nitrogen 30:1), and inorganic compounds (less than 25 %);

- waste particlessize (optimal size is 25-35 mm);

- waste active reaction (рН) (optimal рН is 6.5-7.6);

- degree of output contamination by mesophilic and thermophilic microorganisms (artificial inoculation is carried out for stimulation of purification);

- thermal conditions (more quickly temperature will rise in the thickness of waste, better and more reliable biochemical destruction of organic substances and pathogenic microflora will be).

Sanitary inspection of systems of waste collection, transportation and disposal requires objective assessment of their efficiency, which is impossible without territory sanitary survey, soil sampling and its laboratory analysis.

METHOD OF DETERMINATION OF CONCENTRATION OF СО2 IN THE AIR AS INDEXES OF ANTROPOGENIC CONTAMINATION OF AIR AND VENTILATION OF APARTMENTS. CONCEPT ABOUT AN AIR CUBE, NECESSARY AND ACTUAL VOLUME AND DIFFERENT TYPES OF VENTILATION, THEIR SCIENTIFIC GROUNDING.

Chemical composition of atmospheric air.

http://www.melbourne.vic.gov.au/info.cfm?top=171&pa=1943&pg=1934

Role of air in human health:

Air plays a vital role in our lives. It is our immediate environment and performs following functions.

§        Supply oxygen for living

§        Supply CO2 to plants.

§        Keeps body cool.

§        Helps in smelling.

§        Helps in listening.

Composition:

Air is a mechanical mixture of gases. The normal composition of external air i.e. fresh air and of expired air is given below.

Gases

Fresh Air

Expired Air

Oxygen

Carbon dioxide

Nitrogen

20.93%

0.03 %

 78.1 %

16.9%

 4.4 %

78.1 %

Minute amounts of other gases is present e.g. argon, neon, krypton, xenon and Helium.

In addition to gases, air also contains water vapour, traces of ammonia and suspended matter such as dust, bacteria, spores and vegetable debris.

 Under ordinary conditions the composition of outdoor air is remarkably constant. This is brought about by certain self-cleansing mechanisms which operate in nature such as movement of air, sunlight, rain, atmospheric temperature and plant life.

http://www.treepics.co.uk/education/co2cycle.php

Air content change in act of breathing.

The contents of the carbon dioxide in the external atmosphere is from 0,03 to 0,04 %. The increased contents of carbon dioxide have the negative influence on the human organism:

a)     3 % - the acceleration and deepening of breathing;

b)    4 % - besides this the feeling of head pressure, headache, the noise in the ears, psychical excitement, heartbeeting, slowing down of the pulse, sometimes vomiting and syncope appear;

c)     6-8 % - the above mentioned phenomena intensify;

d)    10 % - stop of breathing;

e)     more than 10 % - paralysis of the brain centers and the death appear in some minutes.

  The individual sensitivity to the carbon dioxide varies in different people. The patients with heart and lung diseases suffer more. 

 In the bad aired and overpopulated rooms the air has the specific smell because of the pollution from the products of the skin perspiration. Simultaneously in such rooms  the humidity and the air temperature increase. Because of that in people appear   headache , the appetite loss, the decreasing of the capacity for work and other violations.

There are the norms of  the contents of carbon dioxide in living room, classroom (not more than 0,5-1%) in same time (the bomb and gas shelters )- not more than 2 %.

Indoor Air Pollution

http://www.sustainablenc.org/thewaytogo/main/iaq.htm

We haves pent a considerable amount of effort and money to control the major outdoor air pollutants, but we have only recently become aware of the dangers of indoor air pollutants.

The EPA has found that concentrations of toxic air pollutants are consistently higher that outdoors – up to twenty times higher for some toxins.  Furthermore, people generally spend more time inside than out and therefore are exposed to higher doses of these pollutants.

Pollution is perhaps most harmful at an often unrecognised site—inside the homes and buildings where we spend most of our time. Indoor pollutants include tobacco smoke; radon, an invisible radioactive gas that enters homes from the ground in some regions; and chemicals released from synthetic carpets and furniture, pesticides, and household cleaners.

Pollutants may accumulate to reach much higher levels than they do outside, where natural air currents disperse them. Indoor air levels of many pollutants may be 2 to 5 times, and occasionally more than 100 times, higher than outdoor levels. These levels of indoor air pollutants are especially harmful because people spend as much as 90 percent of their time living, working, and playing indoors. Inefficient or improperly vented heaters are particularly dangerous.

Smoking is without doubt the most important air pollutant in the United States in terms of human health. The Surgeon General estimates that 400000people die each year in the United States from emphysema, heart attacks, strokes, lung cancer, or other diseases caused by smoking. Banning smoking probably would save more lives than any other pollution-control measure.

Other major indoor air pollution health hazards include asbestos, formaldehyde, vinyl chloride, radon, and combustion gases. Asbestos was widely used in floor and ceiling tiles, plaster, cement, insulation, and soundproofing. It is a serious concern in indoor air because if its carcinogenicity. Formaldehyde is used in more than 3 thousand products, including such building materials as particle board, waferboard, and urea-formaldehyde foam insulation. Vinyl chloride is used in plastic plumbing pipe, floor and wall coverings, and countertops. New carpets and drapes typically contain two doses chemicals designed to kill bacteria and molds, resist stains, bind fibers, and retain colors.

In many cases, indoor air in home has concentrations of chemicals that would be illegal outside or in the workplace. The EPA has found that concentrations of such compounds as chlorophorm, benzene, carbon tetrachloride, formaldehyde, and styrene can be seventy times higher in indoor air than in outdoor air. Many people are highly sensitive to these chemicals, and it is not uncommon to trace illness to a “sick house syndrome” caused by polluted indoor air. Next to smoking, the most serious indoor air pollutant in the United States is probably radon gas that leaks into houses from surrounding soil and rock.

In the less-developed countries of Africa, Asia and Latin America where such organic fuels firewood, charcoal, dried dung, and agricultural wastes make up the majority of household energy, smoky, poorly ventilated heating and cooking fires represent the greatest source of indoor air pollution. The World Health Organization estimates that 2.5 billion people – half the world’s population – are adversely affected by pollution from this source. Women especially spend long hours each day cooking over open fires or unventilated stoves in enclosed spaces. The levels of carbon monoxide, particulates, aldehydes, and other toxic chemicals can be one hundred times higher than would be legal for outdoor ambient concentrations in the United States. Designing and building cheap, efficient, nonpolluting energy sources for the developing countries would not only save shrinking forests but would make a major impact on health as well.

Methods and devices of the air sampling for chemical analysis

There are two groups of methods – laboratory and express. These methods were elaborated and are widely used in the sanitary inspection units for determination of the air pollution in the atmosphere, indoor and in factory working areas.

The aspiration method of the air sampling is one of the laboratory methods. Using this method of sampling the required air volume is passed though selected absorbing solutions in absorbing devices of different constructions (fig. 2) by an aqueous aspirator (fig. 1-a), a vacuum cleaner or the electrical aspirator (fig. 1-b). The investigated air is delivered into the absorbing solution though the long tube of this device, then it is passed by short tube of the aspirator. Crystal absorbing reagents located in tubes – allonges of special forms are widely used for this purpose.

The air volume passed though the absorbing solution or the allonge is determined using a gas meter, an aqueous rheometer (fig. 10.3) or a ball rotameter measuring the air aspiration speed in l/min. The gas meter or rheometer is concatenated between the absorbing device and the aspirator. The required air volume is determined for the particular chemical research (analyses) in accordance to the appendix 2.

The air sampling for laboratory analyses may be selected in tubes of definite capacities by blowing the investigated indoor air through them, or by pouring the water out from the tube inside the investigated room. Gas pipettes (fig. 10.4), flasks and other devices are used.

The universal gas-analyzer UG-2 (УГ-2) (fig. 10.5, appendix 3), the gas-analyzer GMK-3 (ГМК-3) (fig. 10.6) and other devices may be used for the express methods.

 

Fig. 1 а – Aqueous aspirator (1), connected by rubber tube (2) with absorbing devices; b – electrical aspirator „Liot

Fig. 2 Absorbing devices for the air sampling with liquid solutions

а – Zaitzev (Зайцева);

dPetri (Петрі);

bPolezhaev (Полєжаєва);

e – with porous membrane (з пористою пластинкою);

cRikhter (Ріхтера);

fwith crystal reagent (з кристалічним реактивом).

Fig. 3 Aqueous rheometer

Fig . 4 Air sampling into gas pipettes:

аby air inflow (leak-in) or pouring out; bby siphon method.

Fig. 5 Universal gas-analyzer UG-2 (УГ-2) with the coloristical scale

Determination of chemical pollutants in the air using gas-analyzer UG-2 (УГ-2)

The gas-analyzer is built using the linear-colorimetric principle: concentration of a chemical pollutant in the air is determined by the coloring of the indicating reagent in a glass pipe after blowing the certain volume of the investigated air though this. The indicating tube with the reagent is put on to the colorimetric scale. The different scale is provided with the device for each air pollutant. Concentration of the searched substance is pointed on this ruler in mg/m3.

14 chemical pollutants, usually met at manufacture may be determined using this device: ammonia, acetone, acetylene, benzene, benzole, xylol, carbon oxide, nitric oxides, sulfurous anhydride, hydrogen sulfide, toluol, oil hydrocarbons, chlorine, ethylic ether.

The indicating tubes with crystal reagents are prepared for the analyses and are added to the device.

Order of testing. Using rod with the required air volume for certain analysis the air is blown from the air inlet siphon (rubber camera stretched by the spring) at the place of investigation (on the department, on the working place, at the pollution outburst spots). The certain indicating tube is connected to the rubber tube of the device and the required air volume is blown though the rubber tube after releasing the rod from holding clamp. The indicating tube is put onto the colorimetric ruler. The investigated pollutant concentration is determined by the changing of the length of the reagent portion, that changes its color (becomes darkened).

Note. The indicating tubes and air pollution simulation by certain substance are prepared by the laboratory of the department because of the limited working time.

Hygienic characteristics of the indoor sanitary condition and ventilation

1.        The chemical composition of the atmospheric air is: nitrogen – 78.1%; oxygen – 21.0%; carbon dioxide – 0.03-0.04%; inert gases – 0.7-1.0%; moisture usually from 40-60% till the full saturation; dust, microorganisms, natural and anthropogenic pollutions depending on the industrial development of the region, surface type (desert, forest-covered region etc.)

2.        The main air pollution sources of the inhabited regions and industrial areas are the production plants, motorized transport; industrial dust and gas; meteorological factors (winds) and surface type of the regions (dust storms of arid settlements without green plantations).

3.        The main air pollution sources of the residential, communal, domestic and public premises are the products of the human metabolism, generated by skin and respiration (sweat, skin fat, necrotic epidermis degradation products and others). These products are thrown out into the indoor air proportionally to the number of people present and duration of their stay indoor and carbon dioxide volume. The carbon dioxide is accumulated in the air in proportion to the listed pollutants and may be used as an indicator of the pollution with these products.

4.        The organic metabolic products are extracted though the skin and by respiration generally. That is why the air oxidability was suggested as the other pollution indicator for the assessment of the indoor air pollution induced by human. The oxidability index is measured as the atomic oxygen volume required for oxidization of organic products in 1 m3 of the air using the solution of potassium dichromate К2Сr2О7 for titration.

The air is pure if this index doesn’t exceed 4-6 mg/m3. The oxidability air index may be 20 and above mg/m3 in the rooms with the adverse sanitary state.

5. Indoor carbon dioxide concentration is increased proportionally to the number of people and duration of their stay inside. Although it normally does not reach the hazardous levels, nevertheless it does indicate the level of the air pollution with the other metabolism products. The carbon dioxide concentration may reach the hazardous for human organism or even life level only in the enclosed non-ventilated areas (dug-outs, submarines, underground openings, industrial areas, sewer systems etc.) due to fermentation, combustion, putrefaction.

The increase of the СО2 concentration by 2-2.5% does not cause noticeable deviations in the human health and work ability, according to the research by M.P. Brestkin and other authors. Concentrations up to 4% may cause the increase in the respiration intensity, the cardio-vascular functions and reduction of the work capacity. Concentrations up to 5% are accompanied with dyspnea, increase of the cardiac function, decrease of workability. 6% СО2 concentration causes the mental activity decrease, the headaches, dizziness; 7% causes the inability to control oneself, fainting and even death. 10% concentration results in rapid, and in 15-20% cases - sudden death because of the respiratory paralysis.

Some methods were elaborated for CO2 concentration determination in the air: method with barium hydrate by Subbotin-Nagorskiy, methods by Reberg-Vinokurov, Kalmikov, interferometrical method. The portable express method by Lunge-Zeckendorf modified by D.V. Prokhorov is the most widely used in the sanitary practice (see appendix 2).

Carbon dioxide determination in the air using the express method by Lunge-Cekkendorf, modified by D.V. Prokhorov

The method is based on blowing the investigated air through the sodium carbonate (or ammonia) volumetric solution in presence of the phenol-phthalein. The Na2CO3+H2O+CO2=2NaHCO3 reaction takes place in this case. Pink in the alkaline medium, the phenol-phthalein is discoloured after the contact with CO2 (acid medium).

The raw solution is prepared by dilution of 5.3 g chemically pure Na2CO3 into 100 ml of distilled water and 0.1% solution of phenol-phthalein is added to the raw solution. Before analysis the work solution is prepared by dilation of 2 ml raw solution to 10 ml by distilled water.

The solution is poured into Drecsel’s bottle by Lunge-Zeckendorf method (fig. 11.1-а) or into Janet’s syringe in Prokhorov’s modification (fig. 11.1-b). In the first case the rubber syringe with valve or small aperture (hole) is connected with the long tube of Drecsel’s bottle with thin beak. The investigated air is blown though the solution by slow compression and fast release. The bottle is shaken up till the total absorption of CO2 from the air sample after each blowing. In the second case (Prokhorov’s modification) the total air volume is collected into the Janet’s syringe, filled with 10 ml of the work soda solution with phenol-phthalein and held with the cannula up, the syringe is also shaken up. The air volumes for discoloring of the solution are calculated. The air analysis is carried out indoor and outside (atmospheric air).

The result is calculated by the inverse proportion under comparison of the used syringe volumes quantities and CO2 concentration in the atmospheric air (0.04%) and unknown СО2 concentration in the certain investigated indoor premise. For example, 10 syringes were used indoors and 50 - outdoors. CO2 concentration indoors =  (0.04×50) : 10 = 0.2%

CO2 maximum allowable concentration (MAC) of the indoors (premises of various purpose) is determined at the level 0.07-0.1%, in industrial premises where CO2 is accumulated during manufacture processes - 1-1.5%.

Fig. Device for determination of СО2 concentration by Lunge-Cekkendorf

(аrubber syringe for the air blowing with valve; бDrecksel’s bottle with soda solution and phenol-phthalein)

 

Fig. Janets syringe for determination of СО2 concentration by D.V. Prokhorov

Methods of determination and hygienic assessment of the air circulation and indoor ventilation

The indoor air is considered pure if CO2 concentration does not exceed the maximum allowable concentrations – 0.07% (0.7‰) by Pettencofer or 0.1% (1.0‰) by Flugge.

In accordance to this statement the required ventilation volume is calculated. The required ventilation volume is the volume of the fresh air, which is to be drawn inside so, that CO2 concentration does not exceed the allowable value. This volume is calculated using the following formula:

V=

where: Vventilation volume, m3/hour;

К – volume of СО2, expired by one person per hour (in calm conditions 21.6 l/hour; while sleep – 16 l/hour; performing the job of different heaviness – 30-40 l/hour);

nthe number of people inside;

РСО2 maximum allowable concentration in pro mil (0.7 or 1.0‰);

Р1СО2 concentration in the atmospheric air in pro mil (0.4‰).

The calculation of the СО2 volume expired by one person per hour is based on the CO2 concentration in the expired air (4%), inspiration and expiration rate (under calm conditions – 18 inspirations per minute × 60 = 1080 per hour) and expired air volume – 0.5 l per one expiration, and this totals to:

1080 × 0,5 = 540 l/hour.

Using the following proportion: 4 l100 l, х540 l, the expired CO2 volume may be calculated:

х =  = 21.6 l/hour

The respiration rate, expired СО2 volume and required ventilation volume are increased during the physical activity in proportion to their heaviness and intensity.

Required ventilation rate (air exchange rate) is the number, demonstrating how many times the indoor air has to be completely renewed by the ventilation so, that СО2 concentration does not exceed the maximum allowable concentration (MAC).

Required ventilation rate (air exchange rate) is found by dividing the calculated required ventilation volume by the indoor cubature.

Actual ventilation volume is found by determination of the ventilation source area and the speed of the air movement through it (e.g. transom, wicket). The air volume equal to the indoor cubage (cubature) is drawn inside through the wall perforations, windows slits and doors, and it must be added to the volume of the air, drawn through the ventilation.

Actual ventilation rate (air exchange rate) is calculated by dividing the actual ventilation volume by the indoor cubage (cubature).

The indoor air change efficiency may be determined comparing the required and actual volumes and ventilation rates.

The air ventilation rate standards for different premises

Type of premises

Ventilation rate, per hour

outlet ventilation

inlet ventilation

Building norms and rules 2.08.02-89 – patient care institutions

Adult ward

80 m3 per 1 bed

 

Prenatal ward,

dressing ward

1.5 times/hour

2 times/hour

Delivery room, preoperative and operative wards

8 times/hour

 

Postnatal ward

80 m3 per 1 bed

 

Children ward

80 m3 per 1 bed

 

Box, semi-box

2.5 times/hour into corridor

2.5 times/hour

Consulting room

1 time/hour

1 time/hour

Building norms and rules 2.08.01-89 – residential premises

Living room

 

3 m3/hour on 1 m2 of the area

Gasified kitchen

 

90 m3 /hour

Lavatory, bathroom

 

25 m3/hour

State building norms and rules 2.2-3-97 – Buildings and constructions of educational institutions

Classrooms, study area

16 m3 per 1 person

1 time/hour

Workshop

20 m3 per 1 person

1 time/hour

Gym

80 m3 per 1 person

1 time/hour

Teacher’s common room

 

1.5 times/hour

 

 

Effects of Air Pollution

So far we have looked at the major types and sources of air pol­lutants. Now we will turn our attention to the effects of those pollutants on human health, physical materials, ecosystems and global climate.

The primary human health effects of most air pollutants seems to be injury of delicate tissues, usually by damaging cellular membranes. This often sets in motion an inflammatory re­sponse, a complex series of interactions between damaged cells, surrounding tissues, and the immune system. One of the first symptoms of inflammation is leakage of fluid (plasma) from blood vessels. Exposure of respiratory tissues to severe irritants can result in so much edema (fluid accumulation) in the lungs that one effectively drowns.

Bronchitis is a persistent inflammation of bronchi and bronchioles (large and small airways in the lung) that causes a painful cough, copious production of sputum (mucus and dead cells), and involuntary muscle spasms that constrict airways.

Acute bronchitis can obstruct airways so severely that death results. Smoking is undoubtedly the largest cause of chronic bronchitis in most countries. Persistent smog and acid aerosols also can cause this disease.

Severe bronchitis can lead to emphysema, an irreversible obstructive lung disease in which airways become permanently constricted and alveoli are damaged or even destroyed. Stag­nant air trapped in blocked airways swells the tiny air sacs in the lung (alveoli), blocking blood circulation. As cells die from lack of oxygen and nutrients, the walls of the alveoli break down, creating large empty spaces incapable of gas ex­change (fig. 18.10). Thickened walls of the bronchioles lose elasticity and breathing becomes more difficult. Victims of emphysema make a characteristic whistling sound when they breathe. Often they need supplementary oxygen to make up for reduced respiratory capacity.

Cardiovascular stress from lack of oxygen in the blood is a common complication of all obstructive lung diseases. About twice as many people die of heart failure associated with smoking as die of lung cancer.

Irritants in the air are so widespread that about half of all lungs examined at autopsy in the United States have some de­gree of alveolar deterioration. The Office of Technology As­sessment (OTA) estimates that 250,000 people suffer from pollution-related bronchitis and emphysema in the United States, and some 50,000 excess deaths each year are attribut­able to complications of these diseases, which are probably second only to heart attack as a cause of death.

Asthma is a distressing disease characterized by unpre­dictable and disabling shortness of breath caused by sudden episodes of muscle spasms in the bronchial walls. These attacks are often triggered by inhaling allergens, such as dust, pollen, an­imal dander, or corrosive gases. In some cases, there is no apparent external factor, and internal release of triggering agents is suspected. It isn't known whether asthma is genetic, environmental, or a combination of the two.

Fibrosis is the general name for accumulation of scar tissue in the lung. Among the materials that cause fibrosis are silica or coal dust, asbestos, glass fibers, beryllium and aluminum whiskers, metal fumes, cotton lint, and irritating chemicals, such as the herbicide paraquat. We give each of these diseases an individual name (silicosis, black lung, asbestosis, beryllium lung disease, brown lung, or paraquat lung), but they really are very similar in development and effect. Cells respond to irritants and foreign material in the lungs by sealing off damaged areas with scar tissue (produced ei­ther by interstitial cells in the walls of airways or by the ep­ithelial linings). As the lung fills up with fibrofic tissue, respiration is blocked and one slowly suffocates. In some cases, cell growth stimulated by the presence of foreign material in the lung results in tumor formation. Lung cancers are often lethal.

Local and regional pollution take place in the lowest layer of the atmosphere, the troposphere, which at its widest extends from Earth's surface to about 16 km. The troposphere is the region in which most weather occurs. If the load of pollutants added to the troposphere were equally distributed, the pollutants would be spread over vast areas and the air pollution might almost escape our notice. Pollution sources tend to be concentrated, however, especially in cities. In the weather phenomenon known as thermal inversion, a layer of cooler air is trapped near the ground by a layer of warmer air above. When this occurs, normal air mixing almost ceases and pollutants are trapped in the lower layer. Local topography, or the shape of the land, can worsen this effect—an area ringed by mountains, for example, can become a pollution trap.

Smog is intense local pollution usually trapped by a thermal inversion. Before the age of the automobile, most smog came from burning coal. In 19th-century London, smog was so severe that street lights were turned on by noon because soot and smog darkened the midday sky. Burning gasoline in motor vehicles is the main source of smog in most regions today. Powered by sunlight, oxides of nitrogen and volatile organic compounds react in the atmosphere to produce photochemical smog. Smog contains ozone, a form of oxygen gas made up of molecules with three oxygen atoms rather than the normal two. Ozone in the lower atmosphere is a poison—it damages vegetation, kills trees, irritates lung tissues, and attacks rubber. Environmental officials measure ozone to determine the severity of smog. When the ozone level is high, other pollutants, including carbon monoxide, are usually present at high levels as well.

  In the presence of atmospheric moisture, sulfur dioxide and oxides of nitrogen turn into droplets of pure acid floating in smog. These airborne acids are bad for the lungs and attack anything made of limestone, marble, or metal. In cities around the world, smog acids are eroding precious artifacts, including the Parthenon temple in Athens, Greece, and the Taj Mahal in Agra, India. Oxides of nitrogen and sulfur dioxide pollute places far from the points where they are released into the air. Carried by winds in the troposphere, they can reach distant regions where they descend in acid form, usually as rain or snow. Such acid precipitation can burn the leaves of plants and make lakes too acidic to support fish and other living things. Because of acidification, sensitive species such as the popular brook trout can no longer survive in many lakes and streams in the eastern United States.

Smog spoils views and makes outdoor activity unpleasant. For the very young, the very old, and people who suffer from asthma or heart disease, the effects of smog are even worse: It may cause headaches or dizziness and can cause breathing difficulties. In extreme cases, smog can lead to mass illness and death, mainly from carbon monoxide poisoning. In 1948 in the steel-mill town of Donora, Pennsylvania, intense local smog killed 19 people. In 1952 in London about 4,000 people died in one of the notorious smog events known as London Fogs; in 1962 another 700 Londoners died.

Air pollution can expand beyond a regional area to cause global effects. The stratosphere is the layer of the atmosphere between 16 km (10 mi) and 50 km (30 mi) above sea level. It is rich in ozone, the same molecule that acts as a pollutant when found at lower levels of the atmosphere in urban smog. Up at the stratospheric level, however, ozone forms a protective layer that serves a vital function: It absorbs the wavelength of solar radiation known as ultraviolet-B (UV-B). UV-B damages deoxyribonucleic acid (DNA), the genetic molecule found in every living cell, increasing the risk of such problems as cancer in humans. Because of its protective function, the ozone layer is essential to life on Earth.

With stronger pollution controls and less reliance on coal for heat, today’s chronic smog is rarely so obviously deadly. However, under adverse weather conditions, accidental releases of toxic substances can be equally disastrous. The worst such accident occurred in 1984 in Bhopal, India, when methyl isocyanate released from an American-owned factory during a thermal inversion caused more than 3,800 deaths.

 Several pollutants attack the ozone layer. Chief among them is the class of chemicals known as chlorofluorocarbons (CFCs), formerly used as refrigerants (notably in air conditioners), as agents in several manufacturing processes, and as propellants in spray cans. CFC molecules are virtually indestructible until they reach the stratosphere. Here, intense ultraviolet radiation breaks the CFC molecules apart, releasing the chlorine atoms they contain. These chlorine atoms begin reacting with ozone, breaking it down into ordinary oxygen molecules that do not absorb UV-B. The chlorine acts as a catalyst—that is, it takes part in several chemical reactions—yet at the end emerges unchanged and able to react again. A single chlorine atom can destroy up to 100,000 ozone molecules in the stratosphere. Other pollutants, including nitrous oxide from fertilizers and the pesticide methyl bromide, also attack atmospheric ozone.

  Scientists are finding that under this assault the protective ozone layer in the stratosphere is thinning. In the Antarctic region, it vanishes almost entirely for a few weeks every year. Although CFC use has been greatly reduced in recent years and will soon be prohibited worldwide, CFC molecules already released into the lower atmosphere will be making their way to the stratosphere for decades, and further ozone loss is expected. As a result, experts anticipate an increase in skin cancers, more cataracts (clouding of the lens of the eye), and reduced yields of some food crops.

Table 1:  Sources, Health and Welfare Effects for Criteria 

Pollutant

Description 

Sources 

Health Effects

Welfare Effects

Carbon Monoxide (CO)

Colorless, odorless gas 

Motor vehicle exhaust, indoor sources include kerosene or wood burning stoves. 

Headaches, reduced mental alertness, heart attack, cardiovascular diseases, impaired fetal development, death. 

Contribute to the formation of smog. 

Sulfur Dioxide (SO2) 

Colorless gas that dissolves in water vapor to form acid, and interact with other gases and particles in the air. 

Coal-fired power plants, petroleum refineries, manufacture of sulfuric acid and smelting of ores containing sulfur.

Eye irritation, wheezing, chest tightness, shortness of breath, lung damage. 

Contribute to the formation of acid rain, visibility impairment, plant and water damage, aesthetic damage.

Nitrogen Dioxide (NO2) 

Reddish brown, highly reactive gas. 

Motor vehicles, electric utilities, and other industrial, commercial, and residential sources that burn fuels. 

Susceptibility to respiratory infections, irritation of the lung and respiratory symptoms (e.g., cough, chest pain, difficulty breathing).

Contribute to the formation of smog, acid rain, water quality deterioration, global warming, and visibility impairment.

Ozone (O3)

Gaseous pollutant when it is formed in the troposphere.

Vehicle exhaust and certain other fumes.  Formed from other air pollutants in the presence of sunlight. 

Eye and throat irritation, coughing, respiratory tract problems, asthma, lung damage. 

Plant and ecosystem damage.

Lead (Pb) 

Metallic element 

Metal refineries, lead smelters, battery manufacturers, iron and steel producers. 

Anemia, high blood pressure, brain and kidney damage, neurological disorders, cancer, lowered IQ. 

Affects animals and plants, affects aquatic ecosystems. 

Particulate Matter (PM)

Very small particles of soot, dust, or other matter, including tiny droplets of liquids. 

Diesel engines, power plants, industries, windblown dust, wood stoves. 

Eye irritation, asthma, bronchitis, lung damage, cancer, heavy metal poisoning, cardiovascular effects. 

Visibility impairment, atmospheric deposition, aesthetic damage. 

 

 

Systems of Ventilation

http://www.minesafe.org/underground/ventilation.htmlventil

(a) Natural Ventilation. This is greatly achieved by building houses having sufficient open space and by having a large number of windows opening direct into the open air. It largely depends on the following three natural for­ces:

(1)       Diffusion of Gases. Gases diffuse inversely as the square root of their densities, so the air of room diffuses through the cracks and crevices of various doors and windows of a room, even though they are closed. But under ordinary circumstances, the diffusion if there be any, is-very small. So one cannot depend upon diffusion alone. Diffusion causes the gaseous impurities of the respired air to mix up with the fresh air of the room until homogeneity is established. Diffusion, however, does not affect the suspended matter present in the air which tends to fall back towards the earth in the still atmosphere, due to gravitational force.

(2)       Effects of Differences of Temperature. When air is heated, it expands and becomes lighter. This hot air rises up and the cold fresh air rushes in to take its place.

If the air of a room is heated by fire or gets heated from the products of respiration of men and animals or be made more or less moist, it tends to expand and rises up or escapes through all available open­ings, cracks, or crevices. The outer colder air rushes in through outer openings until temperature of both outside and inside air becomes same. Therefore, in all methods of ventilation based upon the force, suitable and adequate inlets for fresh air and outlets for the escape of impure air must be provided. This method is more relied upon in cold countries where coal fires are used and the external and internal dif­ference of temperature of the room is relatively high. But in hot countries, where difference of temperature between the external and the internal air is small, ventilation is imperfect.

(3)       Perflation and Aspiration. Winds are very powerful ventilating agents and they act in two ways: (i) by perflation and (ii) by their aspiration action.

(i) Perflation means the setting up of masses of air in motion and forcing them through open doors, windows and porous bricks into the room as a result of movement of natural air currents. By means of this force the building can be rapidly and continuous­ly flushed with fresh air. Cross ventilation means free perflation between windows and other openings, placed opposite to each other. But natural cross ven­tilation is not feasible in the case of houses having back to back construction. In countries having warm climates, as in India, where the inside and outside temperature of a room is more or less the same, ventilation is promoted by perflating action of the air through doors and windows and as much care should be taken that as far as possible these should be facing each other. Similarly pervious walls such as bamboo matting also allow free perflating without any harm whatsoever.

(ii) Aspiration means the suction action of the wind, which draws air out of a space, creating therein a partial vacuum and thus fresh air rushes in to take its place and a continuous current in perpendicular direction is thus set up. The aspirating action of wind is utilised to ventilate rooms by means of provision of chimneys. When fire is kept burning in the grates, the aspirating action of chimneys is further in­creased.

http://www.minesafe.org/underground/ventilation.html

Natural air supply with mechanical air exhaust 

graphic2

 

This is a popular form of ventilation in residential buildings and offices.

The mechanical air exhaust system creates an underpressure in the building, through which the system is less dependent on the weather than fully natural ventilation. The underpressure creates a pressure difference over the ventilation openings, so air is suck in. But never the less a high wind pressure or temperature difference can result in draught problems. To prevent draught the air supply openings have to be placed as high as possible and the air inlet grid must have a possibility to be regulated.

A controllable exhaust ventilator controls the ventilation capacity. In residential buildings suction takes place from at least the kitchen, the bathroom and the toilet. Suction ducts are needed. In non-residential buildings suction mostly takes place from the corridor.


graphic3

Mechanical Supply and Exhaust

A mechanical ventilation system can be combined with all sorts of heating and cooling systems. Often the heating, cooling and ventilation of a building are combined in the air-conditioning system.

In a mechanical ventilation system the supply air and the exhaust air are transported mechanically.
Advantages of mechanical ventilation are:

1.                      Good control of the ventilation capacity; no dependence of the outdoor weather conditions and despite possible noisy environment

2.                      The possibility of extracting heat from the exhaust air and use it to preheat the fresh air supply (heat recovery)

3.                      The possibility of preheating and pre-cooling of the air supply

4.                      The possibility of humidify and dehumidify of the air supply

5.                      The possibility of cleaning the air by an air filter or supplying the air from a relative clean site of the building

By controlling the ventilators it is possible to control the ventilation capacity of the system. To prevent draught the air supply in the room has to be placed as high as possible. By preheating the incoming air draught problems are also decreased.
The location of the air exhaust grid is of less importance. Even high exhaust velocity can not produce draught. Yet the air exhaust velocity is restricted, because high air velocity (globally above 2 m/s) in the ducts causes noise.
For proper functioning of the system the building has to be sufficiently airtight.

graphic1 graphic4

 

The kinds of the apartments ventilation

Artificial Ventilation. Natural sources of ventilation are not considered practical in Europe and in the case of large buildings, where a number of people are congregated for a considerably long period and where climatic conditions do not permit free use of open doors and windows. Consequently, artificial ventilation is largely resorted to in places such as theatres, cinemas, examination halls and schools. In this system mechanical means are used to facilitate the renewal of air. The systems of artificial ventilation are as follows:

1.     Inflowing ( the fresh air is supplied  into the room by the ventilator, the polluted air is removed by the natural way);

2.     Extract ventilation ( the air from the room is succened off by the ventilator and the fresh air comes naturally);

3.     The inflowing-extract ventilation ( the ventilator succenes the atmospheric air and after the purification, warming and moistening it comes through the inflowing channels).

    The air conditioning is the creation and automatically supporting of the optimal temperature, moisture and the speed of air motion, also the ionization, if needed in the room. There are central and local conditioners.  Conditioned air in the lecture-room, cinemas and other on the  head level must be :

       the air temperature is 20-22ο C,

       the moisture is 40-60%,

       the speed of air motion is 0,15 m/s ( not more than 0,3).

http://irc.nrc-cnrc.gc.ca/pubs/ctus/15_e.html

VENTILATION is a system of intake and exhaust that creates a flow of air.

AIR EXCHANGE - the system of intake and exhaust that occurs with effective air circulation.

Ventilation may be deficient in:

·  confined spaces;

·  facilities failing to provide adequate maintenance of ventilation equipment;

·  facilities operated to maximize energy conservation;

·  windowless areas; and

·  areas with high occupant densities.

Any ventilation deficiency must be verified by measurement.

There are two basic types of ventilation systems:

        natural;

        artificial;

Combination of both is called mixed ventilation.

Artificial ventilation can be general or local, plenty, exhaust or balanced. Combination of general and local ventilation is called combined ventilation.

They used plenty ventilation for prevention of indoor pollution in the operational room, aseptic boxes etc.

Industrial ventilation generally involves the use of supply and exhaust ventilation to control emissions, exposures, and chemical hazards in the workplace. Traditionally, nonindustrial ventilation systems commonly known as heating, ventilating, and air-conditioning (HVAC) systems were built to control temperature, humidity, and odors.

Inadequate or improper ventilation is the cause of about half of all indoor air quality (IAQ) problems in nonindustrial workplaces. This section of the manual addresses ventilation in commercial buildings and industrial facilities.

INDOOR AIR CONTAMINANTS include but are not limited to particulates, pollen, microbial agents, and organic toxins. These can be transported by the ventilation system or originate in the following parts of the ventilation system:

·  wet filters;

·  wet insulation;

·  wet undercoil pans;

·  cooling towers; and

·  evaporative humidifiers.

People exposed to these agents may develop signs and symptoms related to "humidifier fever," "humidifier lung," or "air conditioner lung." In some cases, indoor air quality contaminants cause clinically identifiable conditions such as occupational asthma, reversible airway disease, and hypersensitivity pneumonitis.

VOLATILE ORGANIC AND REACTIVE CHEMICALS (for example, formaldehyde) often contribute to indoor air contamination. The facility's ventilation system may transport reactive chemicals from a source area to other parts of the building. Tobacco smoke contains a number of organic and reactive chemicals and is often carried this way. In some instances the contaminant source may be the outside air. Outside air for ventilation or makeup air for exhaust systems may bring contaminants into the workplace (e.g., vehicle exhaust, fugitive emissions from a neighboring smelter).

General exhaust ventilation (dilution ventilation) is appropriate when:

·   Emission sources contain materials of relatively low hazard. (The degree of hazard is related to toxicity, dose rate, and individual susceptibility);

·   Emission sources are primarily vapors or gases, or small, respirable-size aerosols (those not likely to settle);

·   Emissions occur uniformly;

·   Emissions are widely dispersed;

·   Moderate climatic conditions prevail;

·   Heat is to be removed from the space by flushing it with outside air;

·   Concentrations of vapors are to be reduced in an enclosure; and

·   Portable or mobile emission sources are to be controlled.

Local exhaust ventilating is appropriate when:

·   Emission sources contain materials of relatively high hazard;

·   Emitted materials are primarily larger-diameter particulates (likely to settle);

·   Emissions vary over time;

·   Emission sources consist of point sources;

·   Employees work in the immediate vicinity of the emission source;

·   The plant is located in a severe climate; and

·   Minimizing air turnover is necessary.

MAKE-UP AIR SYSTIS. Exhaust ventilation systems require the replacement of exhausted air. Replacement air is often called make-up air. Replacement air can be supplied naturally by atmospheric pressure through open doors, windows, wall louvers, and adjacent spaces (acceptable), as well as through cracks in walls and windows, beneath doors, and through roof vents (unacceptable). Make-up air can also be provided through dedicated replacement air systems. Generally, exhaust systems are interlocked with a dedicated make-up air system.

Other reasons for designing and providing dedicated make-up air systems are that they:

·   Avoid high-velocity drafts through cracks in walls, under doors, and through windows;

·   Avoid differential pressures on doors, exits, and windows; and

·   Provide an opportunity to temper the replacement air.

If make-up air is not provided, a slight negative pressure will be created in the room and air flow through the exhaust system will be reduced.

HVAC (heating, ventilating, and air-conditioning) is a common term that can also include cooling, humidifying or dehumidifying, or otherwise conditioning air for comfort and health. HVAC also is used for odor control and the maintenance of acceptable concentrations of carbon dioxide.

Air-conditioning has come to include any process that modifies the air for a work or living space: heating or cooling, humidity control, and air cleaning. Historically, air-conditioning has been used in industry to improve or protect machinery, products, and processes. The conditioning of air for humans has become normal and expected. Although the initial costs of air conditioning are high, annual costs may account only for about 1% to 5% of total annual operating expenses. Improved human productivity, lower absenteeism, better health, and reduced housekeeping and maintenance almost always make air-conditioning cost effective.

Mechanical air-handling systems can range from simple to complex. All distribute air in a manner designed to meet ventilation, temperature, humidity, and air-quality requirements established by the user. Individual units may be installed in the space they serve, or central units can serve multiple areas.

HVAC engineers refer to the areas served by an air handling system as zones. The smaller the zone, the greater the likelihood that good control will be achieved; however, equipment and maintenance costs are directly related to the number of zones. Some systems are designed to provide individual control of rooms in a multiple-zone system.

Both the provision and distribution of make-up air are important to the proper functioning of the system. The correct amount of air should be supplied to the space. Supply registers should be positioned to avoid disruption of emission and exposure controls and to aid dilution efforts.

Considerations in designing an air-handling system include volume flow rate, temperature, humidity, and air quality. Equipment selected must be properly sized and may include:

·   outdoor air plenums or ducts

·   filters

·   supply fans and supply air systems

·   heating and cooling coils

·   humidity control equipment

·   supply ducts

·   distribution ducts, boxes, plenums, and registers

·   dampers

·   return air plenums

·   exhaust air provisions

·   return fans

·   controls and instrumentation

REFERENCES:

Principal:

1.                      Hygiene and human ecology. Manual for the students of higher medical institutions/ Under the general editorship of V.G. Bardov. – K., 2009. – PP. 14-34, 71-106.

2.                      Datsenko I.I., Gabovich R.D .Preventive medicine. - K.: Health, 2004, pp. 14-74.

3.                      Lecture on hygiene.

additional:

1.                      Kozak D.V., Sopel O.N., Lototska O.V. General Hygiene and Ecology. – Ternopil: TSMU, 2008. – 248 p.

2.                      Dacenko I.I., Denisuk O.B., Doloshickiy S.L. General hygiene: Manual for practical studies. -Lviv: Svit, 2001. - P. 6-23.

3.                      A hand book of Preventive and Social Medicine. – Yash Pal Bedi / Sixteenth Edition, 2003 –  p. 26-36, 92-97.