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Title: Author: Lototska Olena V.


1
The perspectives of development of preventive
medicine field
  • Author Lototska Olena V.

1
2
THE PLAN
  1. Introduction in hygiene and ecology.
  2. Basic laws of hygiene.
  3. Bases of preventive and current sanitary
    supervision.
  4. Principles of the hygienical setting of norms.
  5. Cosmosphere, sun radiation and health.
  6. Hygienical value of sun radiation, physical
    properties and chemical composition of air
    environment.
  7. Hygienical value of constituents of biosphere
    (atmosphere, hydrosphere, litosphere).

3
Introduction
4
Prevention is better than cure is an old
saying. Preventive medicine deals with the
measures to protect the individuals from the
diseases, and to keep them in a state of positive
health. For this we have to ensure all the
above-mentioned prerequisites required for the
maintenance of positive health. The environments
must be hygienic, with supply of fresh air, safe
potable water and balanced diet.
5
  • Prophylaxis is one of the basic principles of
    public health service. The main duty of the
    medical workers is the taking of the disease
    prevention measures for healthy people and
    exacerbation, complication and relapse prevention
    for the ill.
  • Prophylaxis means the wide system of state,
    public and medical measures for preserving and
    strengthening peoples health, the upbringing of
    the healthy young generation, work capacity and
    peoples longevity increasing.

6
  • Prophylaxis is divided into three kinds
    primary, secondary and tertiary in accordance to
    the specific kinds of pathology.
  • Primary prophylaxis includes prophylactic
    technologies of preventing disease through
    removing risk factors (causes and conditions of
    its development) and improving general body
    resistance to risk factors.
  • Secondary prophylaxis includes medico-prophylactic
    technologies of revealing a disease, preventing
    its progress, aggravation and possible
    complications.
  • Tertiary prophylaxis includes medico-prophylactic
    technologies aimed at removing negative
    aftermaths of the disease (relapses,
    complications, temporary and permanent
    disability, death).

7
Health is defined as a state of complete
physical, mental and social well-being and not
merely absence of disease or infirmity.
8
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9
To promote and maintain a state of health an
individual needs the following prerequisites
  • Supply of fresh air and sunlight
  • Safe and potable water supply
  • Balanced diet
  • Healthful shelter
  • Adequate clothing
  • Protection from communicable and other avoidable
    afflictions
  • Complete sense of protection and security both
    socially and economically
  • hygienic environmental sanitation
  • A congenial social and cultural atmosphere.
  • Regulated way of life with proper rest and
    relaxation and good and simple habits.

10
Medicine
MEDICAL Object of studying sick man
  • PROPHYLACTIC MEDICINE (HYGIENE)
  • Object of studying healthy man, and groups of
    the practically healthy people

11

Hygiene is a basic preventive science in
medicine. It generalizes all dates of theoretical
and clinical disciplines in the field of
prophylaxis, integrates knowledges about complex
influence of an environment on health of the man,
work out principles and systems of preventive
measures.
12
Basic aim of hygiene preserving and improving
health
13
Professor Winslow defined aim of hygiene as
"science and art of (i) preventing diseases, (ii)
prolonging life, and (iii) promoting health and
efficiency through organized community effort
for (a) the sanitation of the environment, (b)
the control of communicable diseases, (c) the
education of the individual or personal hygiene,
(d) the organization of medical and nursing
services for the early diagnosis and preventive
treatment of disease, and (e) the development of
the social machinery to ensure everyone a
standard of living adequate for the
maintenance of health, so organizing these
benefits as to enable every citizen to realize
birth right of health and longevity".
14
  • It has many aspects
  • personal hygiene (proper living habits,
    cleanliness of body and clothing, healthful diet,
    a balanced regimen of rest and exercise)
  • domestic hygiene (sanitary preparation of food,
    cleanliness, and ventilation of the home)
  • public hygiene (supervision of water and food
    supply, containment of communicable disease,
    disposal of garbage and sewage, control of air
    and water pollution)
  • occupational hygiene (measures that minimize
    occupational disease and accident)
  • mental hygiene (recognition of mental and
    emotional factors in healthful living) and so on.

15
Main tasks of hygiene are the following
16
3. Scientific substantiation and working out of
the hygienic norms, rules and measures, which
help use maximum positively influencing on an
organism of the man the factors of an environment
and elimination or restriction up to safe levels
unfavourable operating ones.
1. Studying the natural and anthropogenic
environmental factors and social conditions
affecting the health of a human
2. Studying the laws of the impact of
environmental factors and conditions on the human
body or population.
17
4. Practical implementation of developed
hygienic recommendations, rules and standards in
national economy, controlling and improving their
effectiveness.
5. Forecasting the sanitary situation for the
nearest and remote future, taking into account
plans of the national economy development, proper
hygienic problems arising from the forecasted
situation, scientific research of such problems.
18
Basic methods of hygienic researches
19
Methods of hygiene
1. Methods of environment studying
  • 2. Methods of studying of environmental influence
    on human organism and health

20
Methods of environment studying
Methods of sanitary examination with further
sanitary description
Instrumental and laboratory methods
Physical
Biological
Geographical
Sanitary-statistic
chemical
21
Methods of Studying of Environmental Influence on
Human Organism and Health
Methods of natural observation
Methods of experimental investigation
1.Clinical
1.Experiment with models of natural condition
2. Physiological
3. Biochemical
4. Toxicological
2.Laboratory experiment on animals
5. Sanitary-statistic
3.Laboratory experiment on humans
6. Medical-geographical
22
Environmental Sanitation The word sanitation is
derived from the Latin word Sanitas which means a
state of health.
Environmental Sanitation means the control of
all those factors in man's surroundings, which
cause or may cause adverse effects on his health.
The sanitarian directs his efforts towards
hygiene of water and food supply, hygienic
disposal of human wastes, hygiene of housing and
control of vectors and rodents etc.
23
People in ancient societies were concerned about
personal hygiene and sanitation for religious
reasons. The Bible contains many rules for
cleanliness, and describes public health measures
still important today. These include quarantining
the sick to prevent the spread of disease and
avoiding contact with objects used by sick people.
The Greek physician Hippocrates first made the
connection between disease and natural
environmental factors in the 4th century bc. His
treatise Airs, Waters, and Places described how
diseases can result from way of life, climate,
impure water, and other environmental factors.
For the next 2000 years, it was the most widely
used text on public health and epidemiology.
24
Ancient Romans adopted Greek ideas about public
health after colonizing Greece in the 1st century
bc. Rome's greatest contributions to public
health involved sanitary engineering. They built
aqueducts to supply Rome with pure water and a
public sewer system to carry away wastes, as well
as public baths and hospitals. The Roman
government also hired physicians and assigned
them to villages to care for the poor.
25
After the Roman Empire collapsed in ad 476 public
health efforts were forgotten and unsanitary
conditions returned. Millions of people died when
great epidemics of smallpox, leprosy, bubonic
plague, tuberculosis, and other diseases swept
across Europe in the Middle Ages (5th to 15th
centuries ad).
26
The environments must be hygienic, with supply of
fresh air, safe potable water and balanced diet.
This aspect of preventive medicine started
gaining more importance from 18th century onwards
with the discovery of various vaccines and sera
for the protection against various diseases like
small pox, cholera, plague, whooping cough,
tetanus, tuberculosis, poliomyelitis etc.
27
  • Edward Jenner discovered vaccination against
    small pox in 1796.
  • The discovery of causative agents of the diseases
    by Louis Pasteur (1822-1895) and Robert Koch
    (1843-1910) gave a great fillip to the science of
    preventive medicine.
  • Von Behring (1854-1917) brought up the principle
    of serum treatment and use of anti-sera in
    various diseases.

28
Max von Pettenkofer, 18181901, German chemist
and hygienist. He studied medicine at Munich.
Pettenkofer is considered a founder of
epidemiology and is known for his researches in
the ventilation of dwellings, sewage disposal,
and the spread of cholera. He developed a method
for the quantitative determination of carbon
dioxide.
29
Max Rubner (1854-1932) studied with Voit
constructed the first accurate respiration
calorimeter in Marburg (1889) professor of
hygiene (1891) and professor of physiology (1909)
in Berlin developed concepts of proportionality
of body surface areas to energy requirements
collaborated with Heubner to measure energy needs
of infants.
30
Erisman Fedor (1842-1915) is a founder of
scientific hygiene in Russia. Hes Swiss by
origin. In 1869-1896 he lived in Russia.
Professor of Moscow university (since 1882). He
had classical traits and guidelines in all
principal parts of hygiene. In 1891 he organized
the first sanitary-epidemiological station in
Russia (now - Moscow Research Institute of
Hygiene by Erisman)
31
Dobroslavin Alexey (1842-1889) is a founder of
experimental and military hygiene in Russia. He
created the first hygienic laboratory in
St.-Petersburg.
32
Subbotin Viktor (1844 - 1898) was the first
Ukrainian professor of hygiene. In 1871,
V.Subbotin was elected an assistant-professor of
the Kyiv University and soon appointed a head of
the first Department of Hygiene, Medical Police,
Medical Geography and Statistics. The works by V.
Subbotin were mainly devoted to the problems of
general and communal hygiene. Problems of hygiene
of hospitals, sanitary protection of water
bodies, medical geography occupied the leading
place among them.
33
Ecology is constituted by the total environment
of man. The environment of modern man is partly
natural and partly man-made.
physical factors
social factors
biological factors
1. customs
1. pathogens,
1. air
2. beliefs
2. water
2. microorganisms as well as living beings
3. laws
3. food
4. peculiarities
3. vectors
4. buildings
5. modes of living of human beings
4. plants
34
Environmental standards are definite ranges of
environmental factors which are optimal or the
least dangerous for human life and health. In
Ukraine basic objects of hygienic standardization
are MAC maximum admissible concentration (for
chemical admixtures, dust and other hazards) MAL
maximum admissible level (for physical
factors) LD dose limit (for ionizing
radiation) Optimum and admissible parameters of
microclimate, lighting, solar radiation,
atmospheric pressure and other natural
environmental factors. Optimum and admissible
daily requirements in food and water.
35
Basic objects which are under the hygienic norms
setting can be divided into two groups.
The first group contains factors of
anthropogenous origin which are unfavorable for
human being, and are not necessary for the normal
life activity (dust, noise, vibration, ionizing
radiation, etc.). MAC, MAL and LD are those
parameters which are set for this group of
factors.
The second group contains factors of natural
surrounding which are necessary (in certain
amount) for normal life activity (food-stuffs,
solar radiation, microclimatic factors and
others). For this group the following parameters,
must be set optimum, minimum and maximum
admissible parameters.
36
The methodical scheme of hygienic norms of
substantiation using, the example of MAC for some
toxic substance.
  • The first stage is study physical and chemical
    properties of the substance, elaboration of
    methods of quantitative determination of this
    substance in different subjects, determination of
    its regimen of action on the human (duration,
    interruption, changes of intensity), ways of
    getting into the organism, study migration in
    different elements of the surrounding,
    mathematical prediction of duration of existence
    in different surroundings.

37
The second stage is study direct influence on the
organism. It is started from 'sharp' experiments
the main purpose of which is getting initial
toxicometric data about the substance
(determination of LD50, or LC50 threshold of
strong action (LIMac) and other. With the
knowledge of physical and chemical properties of
the substance, its initial toxicological
characteristics and approximate level of MAC can
be calculated.
38
  • The third stage - is conduction of 'subsharp'
    experiment during l-2 months for determination of
    cumulating coefficient and the most vulnerable
    physiologic systems and organs specification of
    mechanisms of action and metabolism.

39
  • The fourth (basic) stage is carrying out chronic
    experiment which lasts 4-6 months in the case of
    modelling of working conditions, 8-12 - communal
    conditions, 24-36 - in study processes of aging
    or induction of tumours.
  • During the experiment integral parameters are
    studied. They reflect condition of animals,
    degree of strain of regulative systems, functions
    and structure of organs which take part in
    processes of metabolism (activity of enzymes),
    influence of functional loadings.
  • Numbers of MACs of toxic chemical substances in
    the Ukraine are various
  • - for the air of working zone - more than 800,
  • - water- 700,
  • - atmosphere air- 200,
  • - food-stuffs - more than 200,
  • - soil - more than 30.

40
  • The first law of hygiene
  • can be formulated as follows the infringement of
    level of health of the people (disease,
    decreasing of the resistance, immunological
    status, adaptation-compensatory opportunities of
    organism), caused by physical, chemical,
    biological and psychogenic etiological factors,
    can occur only at presence of three driving
    forces
  • source of pollution,
  • mechanism of its influence or ways of its
    transference
  • and human susceptible organism.
  • At the absence of one of these conditions, the
    disturbances of health will not take place.

41
What is pollution?
The word comes from the Latin pollutus, which
means made foul, unclean, or dirty. Some is
obvious like smoke which you can see but much of
it is not obvious at all. Yet you're eating it
and drinking it and breathing it most of the
time. And what is worse is that all this muck
affects all other life on Earth.
42
You can find pollution made by people just about
everywhere on the planet. Even remote places like
the Arctic are badly polluted by nasty chemicals
made by people. The polar bears and seals there
have poisonous chemicals made by people in their
bodies and so do the Inuit people who live with
them. These nasty things kill many animals and
make others sick -- including penguins in the
Antarctic.
43
On a degree of danger distinguish four groups of
chemical substances pollutes I - especially
high toxic (middle death doze -LD5? - is lower
than 50 mg/kg of weight of body) II - high
toxic (LD5? 50 - 200 mg/kg) ? - middle toxic
(LD5? 200 - 1000 mg/kg) IV - low toxic (LD5?-
more than 1000 mg/kg) The concept about first
driving force of process of change of level of
health allows to study laws of change of
polluting substances in an environment, their
decomposition and transformation under influence
of the physical and chemical factors of an
environment. The basic purpose of these measures
is the decreasing of concentration of polluting
substances in an environment up to a level, which
is safety for health of the population.
44
The following ways of toxic, radioactive and
biological agents transmission are possible


AIR
MAN
polluting substance
water
MAN
polluting substance
Animals
Plants

SOIL

polluting substance
MAN
45
Major condition of high stability of the organism
to adverse factors of environment is healthy way
of life, excluding the using of alcoholic drinks,
smoking, other harmful habits, rational
nutrition, rational mode of work and rest,
observance of rules of personal hygiene, using of
wide improving opportunities of physical culture
and sports, self preparing.
46
The second law of hygiene
The second law (negative anthropogenic action) -
people unfavorably influence on the environment
in connection with their physiological, domestic
and industrial action.
  • During the process of live the man allocates in
    environment excrement (faces, urine), which are
    very dangerous in the epidemic and sanitary
    attitude.
  • Human activities can release substances into
    the air, water and soil some of which can cause
    problems for humans, plants, and animals.

47
  • Traditional forms of pollution include
  • air pollution, water pollution, and
    radioactive contamination while a broader
    interpretation of the word has led to the ideas
    of ship pollution, light pollution, and noise
    pollution.

48
  • Serious pollution sources include chemical
    plants, oil refineries, nuclear waste dumps,
    regular garbage dumps (many toxic substances are
    illegally dumped there), incinerators, PVC
    factories, car factories, plastics factories, and
    corporate animal farms creating huge amounts of
    animal waste.
  • Some sources of pollution, such as nuclear
    power plants or oil tankers, can release very
    severe pollution when accidents occur. Some of
    the more common contaminants are chlorinated
    hydrocarbons (CFH), heavy metals like lead (in
    lead paint and until recently in gasoline),
    cadmium (in rechargeable batteries), chromium,
    zinc, arsenic and benzene.

49
Common Sources of Primary Pollutants
  Source  Pollutants Chemical Formulae
Cars, Trucks, Buses    Nitrous oxide,      carbon monoxide,      carbon dioxide,     hydrocarbons  NO2   CO  CO2  CxHy
                     Industry   Nitrous oxide,      carbon monoxide,      carbon dioxide,      hydrocarbons   others          NO2           CO          CO2          CxHy
 Aerosol cans    CFCs         (chlorofluorocarbons),     hydrocarbons    Various
Burning   Coal   Carbon monoxide,     carbon dioxide     sulfur dioxide           CO          CO2          SO2 
50
  • There are several main types of pollution and
    well-known effects of pollution which are
    commonly discussed. These include
  • smog,
  • acid rain,
  • the greenhouse effect,
  • and "holes" in the ozone layer.
  • Each of these problems has serious implications
    for our health and well-being as well as for the
    whole environment.

51

Acid rain forms when moisture in the air
interacts with nitrogen oxide and sulphur dioxide
released by factories, power plants, and motor
vehicles that burn coal or oil.
  • This interaction of gases with water vapour
    forms sulphuric acid and nitric acids. Eventually
    these chemicals fall to earth as precipitation,
    or acid rain. Acid rain pollutants may travel
    long distances, with winds carrying them
    thousands of miles before they fall as dew,
    drizzle, fog, snow or rain.

52
  • Hazards of Acidic Rain .
  • Discoloration of houses,
  • Rusting of metals.
  • Damage of crops.
  • Skin cancer
  • Damage to marine life
  • Lead poisoning due to damage to lead pipes.
  • Prevention
  • i. Treatment of industrial smoke
  • ii. Increase plant growing i.e. Forestation

53
Green House Effect Green houses are glass huts
seen in hilly areas and in the agricultural
processing areas. Mechanism When light falls on
any surface which is transparent, some rays are
reflected and some are refracted. A process of
partial retention of light takes place in the
green house, so temperature in the glass house is
increased.
Causes of Green house effect The air pollution
causes emission of gases like CO2, CH4, CO,
CFC's,NO2,,Chlorine, Methyl chloroform These
gases are known as Green house gases. These gases
cause partial retention of light in the air and
so temperature of the atmosphere increases
54
  • Hazards of Green House Effects
  • Global warming
  • Increased evaporation from sea.
  • Melting of Ice at poles of earth.
  • Increase in sea level.
  • Floods.
  • Disturbance at coastal areas due to increased sea
    level.
  • Prevention
  • Decreased industrialization
  • Treatment of Industrial smoke
  • Check unfit automobiles.

55
  • Damage to the ozone layer is primarily caused
    by the use of chloroflurocarbons (CFCs). Ozone is
    a form of oxygen found in the earth's upper
    atmosphere. The thin layer of ozone molecules in
    the atmosphere absorb some of the sun's
    ultraviolet (UV) rays before it reaches the
    earth's surface, making life on earth possible.
    The depletion of ozone is causing higher levels
    of UV radiation on earth, endangering both plants
    and animals.

56
  • The third law of hygiene (of natural
    pollution)
  • The environment is polluted not only under the
    action of people, but some pollutants come from
    natural sources.
  • Volcanoes spew out ash, acid mists, hydrogen
    sulfide, and other toxic gases.
  • Sea spray and decaying vegetation are major
    sources of reactive sulfur compounds in the air.
  • Forest fires create clouds of smoke that blanket
    whole continents.

57
  • Trees and bushes emit millions of tons of
    volatile organic compounds (terpenes and
    isoprenes).
  • Pollen, spores, viruses, bacteria, and other
    small bits of organic material in the air cause
    widespread suffering from allergies and airborne
    infections.
  • Storms in arid regions raise dust clouds that
    transport millions of tons of soil and can be
    detected half a world away.
  • Bacterial metabolism of decaying vegetation in
    swamps and of cellulose in the guts of termites
    and ruminant animals is responsible for as much
    as two-thirds of the methane (natural gas) in the
    air.

58
The fourth law of hygiene is the law of
positive anthropogenic influence on environmental
of human society. However we must not think,
that the environment is absolutely defenseless in
front of the activity of the man. The nature has
huge resources of self-preservation,
self-updating, self-regulation, maintenance of
ecological balance, self-cleaning, but these
reserves are not boundless.
59
  • Factors Which Keep the Composition of Air
    Constant
  • Wind, which dilutes, sweeps away or
    aspirates the impurities and gets replaced by
    pure air.
  • Rain, which washes the air and removes gases as
    well as suspended impurities.
  • Oxygen and ozone, which oxidise the organic
    matter present in the air.
  • Plants absorb CO2 and give off oxygen in
    sunlight. During sunlight, chlorophyll
    present in green leaves of the plants absorbs
    carbon from carbon dioxide of the atmosphere and
    gives off free oxygen, but at night this process
    gets reversed.
  • Sun affects the temperature, pressure and volume
    of air. Thus heating of air during the day and
    its cooling at night brings about the air
    movements.
  • Changing weather and other climatic and
    meteorological factors affect the direction and
    velocity of air movements over vast a tomospheric
    areas.

60
The fifth law of hygiene
The fifth law of hygiene is the law of inevitable
negative influence of the muddy environment on
health of the population. People also become
ill through exposure to hazards in the
environment. Many diseases are linked to
environmental problems such as polluted drinking
water, poor waste disposal and air and exposure
to mosquitoes and other carriers of disease.
61
Effects of Air Pollution
  • Air pollution can affect our health in many
    ways with both short-term and long-term effects.
    Different groups of individuals are affected by
    air pollution in different ways. Some individuals
    are much more sensitive to pollutants than are
    others. Young children and elderly people often
    suffer more from the effects of air pollution.
  • People with health problems such as asthma, heart
    and lung disease may also suffer more when the
    air is polluted.

62
  • Examples of short-term effects include
    irritation to the eyes, nose and throat, and
    upper respiratory infections such as bronchitis
    and pneumonia. Other symptoms can include
    headaches, nausea, and allergic reactions.
    Short-term air pollution can aggravate the
    medical conditions of individuals with asthma and
    emphysema. In the great "Smog Disaster" in London
    in 1952, four thousand people died in a few days
    due to the high concentrations of pollution.

63
  • Long-term health effects can include chronic
    respiratory disease, lung cancer, heart disease,
    and even damage to the brain, nerves, liver, or
    kidneys. Continual exposure to air pollution
    affects the lungs of growing children and may
    aggravate or complicate medical conditions in the
    elderly. It is estimated that half a million
    people die prematurely every year in the United
    States as a result of smoking cigarettes.

64
Air Pollutant Health Effects
Carbon Monoxide (CO) Colourless and odourless gas.  Reacts with haemoglobin in preference of oxygen. This reduces the amount of oxygen being carried around the body and can result in suffocation. Fortunately, this reaction is slow and requires very high concentrations before advserse effects are felt.
Nitrogen Dioxide (NO2) Brown poisonous gas.  Effects trachea and lungs causing respiratory problems.
Ozone (O3) Colourless gas, slightly sweet odour at low concentrations.  Causes eye irritations at concentration of 0.3ppm and respiratory problems at higher concentrations
PAN gas Effects eyes, nasal passages and respiratry system.
65
The sixth law of hygiene
  • The sixth law of hygiene is the law of
    positive influence of the factors of a natural
    environment on health of the population.
  • The natural factors of the environment (air,
    water, good-quality food) have a positive
    influence on peoples health. They provide
    preservation and strengthening of the human health

66
Good nutrition is a basic component of health.
It is essential for the attainment of normal
growth and development. Not only physical growth
and development, but also the intellectual
development, learning and behavior are affected
by malnutrition. In short, nutrition affects
human health from birth till death.
67
Air is vital to maintain life and serves to
ensure a constant supply of life giving oxygen to
the body through the process of respiration. One
can refuse polluted food and water but not the
polluted air. An unlimited, relatively clean air
is necessary for comfortable and healthful living.
Functions of Air 1. It serves to maintain Life
through constant oxygen supply. 2. It helps in
regulation of body temperature cooling power of
the air being an important factor. 3. It helps in
functioning of sensations like smell and
hearing. 4. The adverse function is through the
polluted air, which becomes a source of
spreading various diseases, whether bacterial or
otherwise.
68
Impurities due to Respiration

Inspired air Expired air
Oxygen 20.95 16.50
Nitrogen 79.02 79.06
C02 0.04 4.44
Water vapours Varies Saturated
Temperature Varies As of body temperature
69
The sun is a source of electromagnetic energy including radio waves, infrared, visible light, ultraviolet, x-rays, gamma rays, and cosmic rays. Each band has its own characteristic wavelengths and properties as a result of wavelength. Visible light is "visible" because its wavelengths can be detected as various colors by the human eye. Ultraviolet, although invisible, also has various wavelengths and properties.
70
Category Wavelength (nanometres, nm) Relevance to life on earth
Ultraviolet (UV) 100-400 Causes short- and long- radiation term damage to exposed living matter, particularly, in humans, sunburn, photoageing and cancer of the skin
Visible light 400-800 Allows us to see enables plants to create food molecules drives human biorhythms lifts human mood
Infrared radiation 800-17,000 Warms our bodies
.
71
The light you can see has a wavelength of 400-760
(nm). UV rays region ? long-wave ultraviolet
radiation ? 315-400 nm region ?
middle-wave ultraviolet radiation ? 280-315
nm region ? short-wave ultraviolet radiation
? 120-280 nm.
72
The solar ultraviolet radiation wave lenght less
then 290 nm is completely absorbed by oxygen and
ozone of the upper atmosphere. Atmospheric
pollution by factory waste helps the ozone layer
destruction resulting in appearance of ozone
holes. The shortest and the most harmful UV
waves reach the earth surface through these
ozone holes.
73
Positive effects UV rays are necessary for our
body to produce vitamin D, a substance that helps
strengthen bones and safeguards against diseases
such as Rickets. Some scientists have shown that
Vitamin D lowers the risk of getting some kinds
of internal cancer, like colon cancer. UV light
is also used as a therapy for psoriasis, a
condition in which the skin sheds its cells too
quickly, resulting in itchy, scaly patches on
various parts of the body. When exposed to
ultraviolet rays, the growth of the skin cells is
slowed, relieving the symptoms. UV rays are also
used in various commercial functions, such as
disinfecting fish tanks and sterilizing medical
equipment. Animal life makes their own use of
these wavelengths toocertain animals can
actually see ultraviolet light, and use it to
their advantage. Bees use the reflection of UV
off of flower petals to guide their pollen
collecting. 
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2.1.
  • Is ultraviolet light harmful?
  • The difference has to do with the ability of UV
    rays to penetrate body surfaces.
  • UV-A is also known as "blacklight" and is
    generally harmless. It results in skin tanning
    and is used in medicine to treat certain skin
    disorders.
  • UV-B has a very high penetrating ability and
    prolonged exposure is responsible for some types
    of skin cancer, skin aging, and cataracts
    (clouding of the lens of the eye).
  • UV-C has extremely low penetrating ability and is
    nearly completely absorbed by the outer, dead
    layer of skin where it does little harm. It does
    reach the most superficial layer of the eye where
    overexposure can cause redddening and painful but
    temporary irritation, but it cannot penetrate to
    the lens of the eye and cannot cause cataracts.
    UV-C is also known as "germicidal UV."

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Over the years, researchers of human comfort have
established the variables that affect a human's
thermal sensations and they have established the
ranges of these variables within which the
average person is comfortable.
Six primary comfort variables These "comfort"
variables include air temperature, relative
humidity, air motion, and mean radiant
temperature. The mean radiant temperature is the
average temperature of all of the surfaces that
surround the person in question. These four
variables are called the "environmental
variables" because they represent the environment
surrounding the body. A second set of
variables, called the "personal" variables, are
controlled by the individual. The two are the
clothing insulation value, termed the "clo"
value, and the metabolism rate.
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Thermoregulation of human organism on 85 is
realized through the skin. The most of the heat
(45 ) organism loses by the emitted radiation,
30 by convection and conduction, 10 by
evaporation (perspiration).
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High humidity of air sharply decreases heat loss
by perspiration. Heat loss by conduction first of
all depends on temperature of subjects contacting
with body, and by convection (circulation) - also
on speed of air moving. Heat loss by convection
is proportional to square root of speed of air
moving (vV). In air temperature 33C heat loss by
convection stops, and in further increase of
temperature body heating takes place. If
temperature of environment is equal to body
temperature heat loss by conduction and radiation
stops. Thus, in conditions of high temperature
and humidity in absence of air moving adaptive
possibilities of thermoregulation are sharply
narrowed and tensed.
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TemperatureTemperature is a measure of the
amount of heat (average molecular kinetic energy)
in a material, such as air. Temperature is the
average amount of moving energy contained by
particles moving around in the atmosphere.Temper
ature is measured with thermometers that may be
calibrated to a variety of temperature scales.
The basic unit of temperature (symbol T ) in the
International System of Units (SI) is the kelvin
(Symbol K). In most of the world, the degree
Celsius scale is used for most temperature
measuring purposes.
Many physical properties of materials including
the phase, density, solubility, vapor pressure,
and electrical conductivity depend on the
temperature. Temperature also plays an important
role in determining the rate and extent to which
chemical reactions occur. This is one reason why
the human body has several elaborate mechanisms
for maintaining the temperature at 37 C, since
temperatures only a few degrees higher can result
in harmful reactions with serious consequences.
Temperature also controls the type and quantity
of thermal radiation emitted from a surface.
79
                           A barometer is used
to measure air pressure. The average pressure
exerted by the atmosphere on sea level is 1 bar.
The millibar (one-thousandth of a bar) is the
unit commonly used to report air
pressure.Generally, air pressure decreases with
higher altitude. Pretend air pressure is like a
column of air reaching into the sky. The higher
up the land is, the shorter the column of air is
on top of it. A shorter column has less mass and
weighs less. As such, there is less air on top of
mountains pushing down than there is down in a
valley.
Air PressureAir pressure is the force of air
pushing down on earth. Air pressure due to
weather is also known as Atmospheric Pressure.
Air pressure is the result of Earths gravity
pulling on the atmosphere.
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Water vapor in the air is called humidity.
Hygrometers are used to measure humidity.
Relative humidity is the amount of water vapor in
a volume of air compared to the maximum amount of
vapor that volume of air could possibly hold.
Relative humidity is measured by a psychrometer
and reported as a percentage.                    
        
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Wind is the movement of air from a location of
high pressure to a location of low pressure as
pressure equalizes. Wind is described in terms of
its direction and speed. Wind vanes are used to
indicate wind direction. Wind vanes point into
the wind, meaning they point in the direction
from which the wind is coming. Winds are named
for the direction from which they are coming.
Anemometers measure wind speed. Wind speed is
reported in kilometers or miles per hour (km/h or
mph), or in centimeters or meters per second
(cm/s or m/s).
83
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