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Topic № 62
HYGIENIC ASSESSMENT OF TROPIC CLIMATE INFLUENCE ON
LIVING CONDITIONS, WORK CAPACITY AND POPULATION HEALTH
1. Learning objective
1.1. Master hygienic peculiarities of working and living conditions of
population in tropic and hot climate.
1.2. Master the method of assessment of heat exchange and organism
thermoregulation of the body in tropic and hot climate.
1.3. Know types of population pathology in tropic and hot climate conditions.
2. Basics
2.1. Y o u s h o u l d k n o w :
2.1.1. Physiologic peculiarities of thermoregulation mechanisms in hot
microclimate conditions and its influence on the organism and health.
2.1.2. Main types of pathology which are common for tropic and hot climate.
2.2. Y o u s h o u l d h a v e t h e f o l l o w i n g s k i l l s :
2.2.1. To determine parameters of the microclimate and its impact on the
organism.
3. Self-training questions
3.1. Hygienic characteristic of climate and weather in tropic and hot climate.
3.2. Hygienic peculiarities of solar radiation in tropic climate.
3.3. Hygienic peculiarities of daily and seasonal microclimate fluctuation (air
temperature, radiant temperature, humidity, air movement speed) in hot deserts and
humid tropic conditions.
3.4. Meteorological factors’ complex influence on heat exchange and other
physiological processes in the organism in tropic and desert climate conditions.
3.5. Hygienic characteristics of savannah, steppe, arid areas and humid tropic
forest climate.
3.6. Health disorders and diseases typical for tropic and hot climate and their
prophylactics.
3.7. Human adaptation and acclimatization in hot and tropic climate.
3.8. Personal hygiene peculiarities in hot and tropic climate: hygiene of skin,
clothes, hygienic principles of day regimen and their substantiation.
3.9. Peculiarities of inhabited area planning and build-up in arid and humid
tropic climate.
3.10. Peculiarities of sanitary infrastructure of settlements in tropic climate.
Water supply, sewerage system, solid waste disposal. The role of green vegetations in
microclimate conditions improvement in inhabited areas.
3.11. Residential hygiene in hot climate. Planning peculiarities of different types
of buildings according to their insolation and influence on residential microclimate
conditions. Optimal windows orientation, its scientific substantiation. Sun protection
devices.
3.12. Hygienic requirements to natural and artificial residential and industrial
premises ventilation in tropic climate.
3.13. Air conditioning in residential, public and industrial premises as
microclimate optimization measure.
3.14. Peculiarities of requirements to natural lighting of residential premises in
tropic conditions. Natural lighting and microclimate optimization measures
interrelations. Venetian blind influence on these factors.
3.15. Hygienic peculiarities of building materials and constructions which are
used for building in tropic climate.
3.16. Organization and working regimen peculiarities in arid and humid climate.
Microclimate parameters in which physical work is impossible.
1.1. Calculation methods of the assessment of tropical climate influence on heat
condition of organism. (see Appendixes).
4. Self- training assignments
4.1. Using tables or nomogram (topic № 8) determine equivalent-effective
temperature (EET) in ship’s hold where dockers are doing the loading work, if air
temperature according to dry thermometer of aspiration psychrometer is tdry = + 330C,
twet = +280C, air movement velocity v = 0.1 m/sec. According to appendix 4 table 4.1,
determine acceptable working time of dockers in the hold. How could work conditions
be optimized?
4.2. Using nomogram (topic № 8) determine the resultant temperature in
residential premise where air temperature according to dry thermometer is t = +320C, air
movement velocity is v = 0.15 m/sec., absolute air humidity is A = 20 Hg mm, average
radiant temperature is t = + 350C. Loader brigade have to do the hard manual work.
Determine possibility of this work performance according to mentioned microclimate
conditions. How could work conditions be optimized? (appendix 4).
4.3. Calculate the wet bulb globe temperature (WBGT) by Yaglow and Minard
(1955) if the air temperature according to dry and wet thermometer of aspiration
psychrometer is tdry = +340C, twet = +300C, the globe thermometer shows, that t = +280C
(appendix 4). Is it possible to do any physical work in such microclimate conditions?
5. Structure and contents of the lesson
This is a seminary lesson. Self–training assignments are checked at the beginning
of the lesson. Theoretical questions according to chapter 3 appendix 1, 2, 3 and
additional literature are worked on by means of students questioning and teacher’s
explanations. (45 min.)
During the second part of the lesson, students work with the situational tasks. The
tasks have been developed by the chair and they contain different variants of
meteorological characteristics of hot climate and task to assess possible health disorders
and diseases according to these conditions.
When doing the tasks students should use methods and standards found in
appendix 4.
6. Literature
6.1. Principal:
6.1.1. Общая гигиена. Пропедевтика гигиены. // Учебник для иностранных
студентов. / Е.И.Гончарук, Ю.И.Кундиев, В.Г. Бардов и др. – К.: Вища школа,
2000. – С. 163-241.
6.1.2. Даценко І.І., Габович Р.Д. Основи загальної і тропічної гігієни. – К.,
Здоров’я, 1995. – С. 22-31, 333-336.
6.1.3. Даценко І.І., Габович Р.Д. Профілактична медицина. Загальна гігієна з
основами екології. Підручник. – 2 видання: К.: Здоров’я, 2004 – С. 697-732.
6.1.4. Общая гигиена. / Г.И.Румянцев, М.П.Воронцов, Е.И. Гончарук и др.–
М.: Медицина, 1990. – С. 64-67, 169-172, 208.
6.1.5. Румянцев Г.И., Козлова Т.А., Вишневская Е.П. Руководство к
практическим занятиям по общей гигиене. – М.: Медицина, 1980. – С. 61-67.
6.1.6. Lecture materials.
6.2. Additional.
6.2.1. Руководство по тропическим болезням. / Под ред. А. Я. Лысенко. –
М.: Медицина, 1983 – С.5-52.
6.2.2. Тропические болезни: Учебник. /Под ред. Е.П. Шуваловой. – М.:
Медицина, 1989. – С. 6-7.
6.2.3. Факторы, влияющие на здоровье в условиях работы при высоких
температурах: Доклад научной группы ВОЗ // Серия технических докладов №
412. – Женева: ВОЗ, 1970.-38 с.
6.2.4. Новожилов Г.Н., Березин А.А. Методы комплексной оценки
микроклимата и наружных метеоусловий. – Л.: Военно-медицинская академия,
1980. – С. 3-17, 27-30, 35-37, 42-43.
6.2.5. .Бардов В.Г, Сучков Б.П. Методические указания по самоподготовке
студентов лечебного факультета по курсу «Гигиенические аспекты профилактики
тропических болезней». – К.: КМИ, 1988. – 32 с.
7. Equipment required for the lesson
1. Tables :
Climatic zones of the Earth with their hygienic characteristic;
Maximum acceptable values of effective-equivalent (EET) and resultant
temperatures (RT);
Nomograms for EET and RT calculations.
2. Formulas for wet bulb globe temperature (WBGT) calculations according to
Yaglow and Minard; formulas to index of thermal loading (ITL) determination
according to Givony.
3. Situational tasks for self–training assignments.
Appendix 1
Hygienic characteristic of tropic climate
From medico–geographical point of view, tropics are a part of the earth surface
situated in equatorial (from 10 north latitude till 10 south latitude), tropical (from 10 till
20 north latitude and from 10 till 20 south latitude) and subtropical climatic (from 20 till
30 north latitude and from 20 till 30 south latitude) zones.
The most of the land belongs to tropics: almost all Africa, South Asia, south of
East Asia, the most part of Latin America, Oceania. The most part of population lives in
tropics and subtropics. Transitional zone adjoins to tropic zone (Mediterranean area,
front and middle Asia, the south of the USA etc.) and it is characterized as tropic and
mild zones from to medico –geographical point of view.
Sun is the source of heat, light and energy for the biosphere. Sun energy causes
air streams and weather changing in the result, determines area climate. All organic life
on the Earth is connected with solar energy.
The amount of solar energy, reaching the Earth surface depends on the
geographic latitude of the locality because it determines noon Sun height above the
horizon and day and night duration. If the angle of sun rays fall angle is close to 900, the
most radiation falls per unit of the horizontal surface and it has shorter way of
penetration through the atmosphere.
Values of angles for different latitudes of the northern hemisphere during the
equinox (on 21.03 and 21.09) and solstice (on 22.06 and 22.12) are shown in table 1.
Table 1
Sun angle in the noon in degrees (for northern hemisphere)
Latitude
Pole
Polar Circle
Tropics
Equator
21.03
0
23.5
66.5
90.0
22.06
23.5
47.0
90.0
66.5
21.09
0
23.5
66.5
90.0
22.12
0
0
43.0
66.0
Climate classification for tropic countries:
1. Steppe climate;
2. Mediterranean climate;
3. Savannah climate;
4. Subtropical and tropical desert climate;
5. Humid tropical forest climate.
Steppe climate
There are two steppe categories. There are steppes, which are situated in mild
latitudes and steppes which are situated in tropic and subtropical latitudes along the
desert periphery.
In summer time in this zone the prevalent air mass is mild zones continental air
which transforms into continental tropical air. There are frequent hot air temperatures
(30-400) with low humidity in summer. Average temperature of the warmest month is
+240C (in steppe of mild latitudes), in steppes of tropical latitude it is 4-60 degrees
more.
In winter it is warm without frost and snow in tropic zone steppes.
It is snowy and temperature decreases to –100 –200 in mild latitudes steppes.
Mediterranean climate
The climate is warm, average temperature of the coldest month is 0 0C, the
warmest month temperature is +22+280C. The summer is hot and dry, sometimes the
temperature reaches +42+450C due to hot winds (sirocco and mistral) from the North
Africa deserts.
Savannah climate
Savannahs are widely spread in the most part of Africa and South America
tropical part, in Hindustan from 22 south latitude, on the Ceylon island, Myanmar
central part, Indo-China, Australia north part, Hawaii.
Savannah is tropical forest–steppe. Gross grass covering develops here at the
beginning of rain periods. There are trees (evergreen and trees which drop their leaves
in dry season) but they don’t form big areas.
In winter dry continental tropical air prevails, brought by trade winds, in summer
there is wet air from equator. That is why wet weather with heavy precipitations is
frequent in summer, the highest average temperature per month is +25…+300C , but in
winter the weather is dry, the lowest average month temperature is +15…..+180C.
Subtropical and tropical deserts climate
The tropical desert is an environment of extremes. This extremity causes people’s
life impossible because of dry sunny and hot weather prevalence. Average summer
month temperature increases to +25…+300C and day temperature in shadow may reach
+40…+500C.
Water-rich air masses are sporadic in subtropical and tropical zones deserts.
Continental tropical air from trade winds loses its humidity before deserts. There are
deserts of Sahara, Libyan, Nubian, Namibia, Kalahari and also Arabia, South America
and central part of Australia deserts. Complete absence of cloudiness, high solar
radiation amount, high air and ground temperature, dryness and high level of
evaporation, limited or complete absence of water resources are common for deserts.
Average annual air temperature is higher than +180C, in some places it reaches
+250C and more. In summer average month air temperature reaches +28…..+37.50C and
it is +32 C.. +36.50C common in the warmest place but it can reach +400C. Day
temperature often reaches +40.. +450C or even +500C (Sahara, Death Valley).
Maximum average month air temperature was +490C and absolute maximum air
temperature in shadow was +55……+630C (Somali, Africa). During the day ground
temperature may increase up to +800C and at night under conditions of clear sky air and
ground temperature decreases to +10….+10C. In winter average month air temperature
is approximately +100C.
Tropical rainforest climate
Tropical rainforest climate is spread in Equatorial Africa, South America, Central
America, west coast of Indo–China, south-west coast of India, Malaccan peninsula,
Philippines, New Guinea and others. It is widely spread along the Congo and the
Amazon rivers. Climate is hot and humid. Average annual air temperature is high
(+240C….+290C). Important peculiarity is that average month air temperature is
monotonous with little difference between the warmest (+27…+280C) and the coldest
(+24...250C) months. Air humidity is 70-80-% and more. Under high radiant
temperatures and little air movement in tropical rainforests the organism heat exchange
is under great physiologic tension.
Climatic conditions of oceans in tropic latitude
Oceanic climate peculiarities are characteristics of open oceanic and sea areas,
islands and seaside zones of continents where sea air masses are spread. Oceanic
climate is characterized by its latitude, atmospheric circulation, warm and cold ocean
streams. Low range of the fluctuations of the daily (1-3) and annual (10-12) air
temperature is common for oceanic climate.
In hot regions of Atlantic, Pacific and Indian oceans there are following zones:
equatorial, equatorial monsoons, tropical and subtropical. In equatorial zone climatic
conditions are not very distinct from climatic conditions of tropic rainforests. Average
month air temperature of the Indian ocean is +27.5...+290C, western part of the Pacific
ocean is +27.5….+28.50C, eastern part – +24.5…260C, in the Atlantic ocean in summer
it is +23…250C, in spring +25…270C. Precipitation rate is 2 000 – 3 000 mm per year.
There are areas of equatorial monsoons (originated from Arabic “mausem” which
means “season” or Urdu/Hindi “mausam”, which means “weather”) in the north and
south from equatorial zone. Humid equatorial air prevails there in summer. The weather
is often with high temperature (per month +25…280C), frequently cloudy, great amount
of precipitations. In winter there is sea tropic air from trade winds. Oceanic monsoons
have great influence on the south of Asia (Hindustan, Indo-China) because they form
here special climate which is characterized by rainy summer.
Appendix 2
Hygienic peculiarities of residential areas build-up as the measure of living and
working population conditions optimization in tropic regions
Urbanization, rural-urban migration, especially in tropical zone of developing
countries, has created the global social problem. According to WHO and UNCHS
information over 1 billion of population are either homeless, or live in slums which are
dangerous to their health.
Among big cities one should mention Mexico City (31 million population), Sao
Paolo (26 million), Calcutta, Lagos and other.
These are the disadvantages related to urbanization in hot regions of the world:
- slums, squatter settlements, which constitute 50-75% of population;
- overload of public transport: journey to work from slums exhausts people;
- rate of traffic accidents mortality is 4-6 times higher than from infections;
- traffic noise causes nervous and mental, cardiovascular disorders rise;
- air pollution from traffic discharges causes chronic bronchitis;
- communicable diseases rate in big cities is twice higher than in rural areas;
- water and food supply is complicated in arid regions.
Following rules of hygiene in city build-up is of great importance as a measure of
living conditions optimization in these regions.
Hygienic peculiarities of urban build-up in hot regions are:
- functional zoning of city areas – residential zone, industrial zone, communal–depot
zone, traffic, recreational (rest zone), waste collection and disposal zones, taking
into account the wind rose, site landscape, level of underground water, usage of
forest areas, planting of greenery in the streets , flooding preventon measures,
creation of open water reservoirs, fountains in recreational areas.
Creation of favourable microclimate conditions in residential and industrial
premises in tropical regions is achieved by:
- premises windows aspect: in the equatorial zone – northward and southward
(long premises – parallel to the equator to decrease direct insolation), in subtropical
zones of the northern hemisphere - south-eastern – south-western (premises length
should be oriented along to heliothermal axis);
- wall thickness increasing to 0.5 m and more, using bricks, high porous concrete,
clay, high building increasing, galleries equipment, balconies. Roofs should be made of
heat-proof materials and project for 2-3 m out of wall borders, double or isolated
ceiling, floor should be made of concrete or stone slabs. There should be awnings over
windows, gratings, venetian blind, through air ventilation due to double–sided windows
location, natural and artificial ventilation, air conditioning.
Appendix 3
Heat exchange and thermal regulation peculiarities of the organism in tropic
climate
Complex microclimate influence on heat exchange was described in the topic # 8.
There you can find the information that in optimal microclimate heat exchange
mechanisms function without physiologic tension. Heat exchange is performed through
the breathing – 12-15% (heating of expired air and moisture evaporation out of lungs
and mucous surface) and through skin: 45-47% by radiation, 28-30 % by conduction
(convection and conduction), 15-18% - by sweat evaporation from the skin surface.
In tropic climate air temperature and radiant temperature from the Sun, heated
soil surface and other solid surfaces (walls, metal cars and others) often can be higher
than human body’s temperature, due to this human body can’t loose heat by radiation,
convection or conduction, and on contrary due to these mechanisms it can get additional
heat. The only mechanism of heat exchange and heat balance is heat output by
evaporation. In dry air (relative humidity is 40%) and wind presence this mechanism
works rather effective which is common for arid climate areas. Under high humidity
and wind absence in humid climate areas this mechanism doesn’t work properly: sweat
is excreted and flows down without evaporation. Due to this there can be overheating,
heat or sun stroke, organism dehydration. Significant amount of salts, microelements
and vitamins is excreted with sweat. And organism demands additional water (up to 5 –
12 and more liters per day).
WHO and UN specialists have developed medical measures to control living and
working conditions in tropic climate and preventive measures which are implemented in
countries of this climate. Calculation methods of heat load determination and
overheating prevention and its pathology are of great importance among medical
measures.
Appendix 4
Hygienic standards and calculation methods of heat load of organism in hot and
tropic climate conditions
4.1. Maximum allowable equivalent-effective temperature (EET) indices.
Table 2
Labour mode
Without breaks during the
shift
With breaks:
-every 3 hours
-every 2 hours
-every 1 hour
-every 30 min
- every 20 min
For people acclimatized
to high temperature
For non-acclimatized to
high temperature people
light
Labour intensity
medium
hard
30.4
28.9
26.1
32.7
33.3
35.0
38.2
40.5
29.9
31.0
32.7
35.5
37.7
27.6
29.9
30.4
34.4
35.0
32.2
29.4
28.9
30.2
27.4
26.9
EET and resultant temperatures are calculated by means of tables and nomograms
(“Self-training assignments” №4 topic # 8).
4.2. Wet bulb globe temperature determination method and its hygienic
assessment according to Yanglow and Minard (1955).
Wet bulb globe temperature (WBGT) is an integral index of environment
temperature which takes into account temperature, air humidity, radiant temperature and
it is calculated by the following formula (1):
WBGT = 0.1 tdry + 0.7 twet + 0.2 tbulb,
(1)
where, WBGT – is wet bulb globe temperature;
tdry – temperature according to dry thermometer of psychrometer indices;
twet – temperature according to wet thermometer of psychrometer indices;
tbulb radiant temperature according to the black globe thermometer.
According to Yanglow and Minard (1955) if WBGT exceeds 29.40C physical
load for non-acclimatized people is limited. Under 31.10C WBGT physical load is
excluded. Under 32.20C WBGT physical load is excluded for acclimatized people too.
Example 1. Dry thermometer of Assman psychrometre tdry =350C, twet = 280C,
tbulb = 370C. WBGT is:
WBGT = 0,1×35 + 0.7×28 + 0.2×37 = 28
Conclusion: human can work and perform light physical work.
Example 2: Dry thermometer index is tdry = 380C, wet thermometer twet = 350C,
globe thermometer tbulb = 400C:
WBGT = 0.1×38 + 0.7×35 + 0.2×40 = 36.3
Conclusion: under these circumstances physical work is impossible for
acclimatized people too.
4.3. Heat–Load Index (HL) according to Belding and Hatch calculation.
According to this method heat-load is calculated by the formula (2);
HL = М  С  R – Еmax. kcal/hour,
(2)
where: M - intensity of metabolism during work: light work –170 kcal per hour;
medium - 300 kcal per hour; hard – 420 kcal per hour;
R – heat exchange through radiation, kcal per hour;
C- heat exchange through convection, kcal per hour;
Emax- maximum acceptable heat loss through sweat evaporation, kcal per hour.
Loss (-) or income (+) of heat by radiation R is calculated by formula (3):
R = 11×(tbulb - 35) kcal/hour,
(3)
where: tglobe – mild radiation temperature according to the globe black thermometer;
Losses (-) or income (+) of heat by convection is calculated by formula (4):
С = 6×v0.6 ×(tdry - 35) kcal/hour,
(4)
where: v - air movement, m/sec. (v is in the table 4.2);
tdry – air temperature according to dry temperature of psychrometer;
35 – surface body temperature.
Table 3
v m/sec 0.05
v0.6
0.17
0.1
0.25
0.2
0.38
0.3
0.49
0.4
0.58
0.5
0.66
0.6
0.74
0.7
0.81
0.8
0.87
0.9
0.94
1.0
0.99
Maximum heat loss through sweat evaporation (Emax) is calculated by formula
(5):
Еmax. = 12×v0.6 ×(42 - р) kcal/hour,
(5)
where: p - maximum water pressure, Hg mm under dry thermometer of psychrometer.
In case of wearing light clothes calculation result of heat load by formula (2) is
divided by 3.
Authors recommend allowable values of heat–load index in the range of no more
than 400-600 kcal per hour. It should be mentioned that with air movement increase
sweat evaporation intensity increases proportionally. Thus this method is used in
conditions of weak air movement.
Example: During the first part of summer (June) workers brigade is working on
cotton plantation performing work of medium intensity. Metabolism intensity rate
M = 300 kcal per hour. Mild radiant environmental temperature according to black
globe thermometer t = 400C; air temperature according to dry thermometer of
psychrometer tdry = 380C; air movement v = 0.05 m/sec.; maximum air humidity
according to dry thermometer (380C) p = 48 Hg mm.
At first loss (-) or income(+) of heat through radiation should be calculated: R=
11×(40 - 35) = 11×5 = + 55 kcal/hour.
Then loss (-) or income (+) of heat through convection should be calculated
C = 6×0.17×(38 - 35) = + 3.06 kcal/hour.
Then the maximum heat loss by sweat evaporation is calculated Еmax. = 12×0.17×
(42 - 48) = - 12.24 kcal/hour.
Consequently, heat load index (HL) will equal HL = 300 + 55 + 3.06 – 12.24 =
345.82 kcal per hour, and for 6 hours of 7 hours working day (1 hour for break and
lunch) the heat load will equal 345.82×6 = 2 074.92 kcal.
Conclusion: The heat stress doesn’t exceed allowable level (400-600 kcal per
hour).
While assessing results of heat exchange of the organism in tropic climate
calculation, one should mention that huge amounts of macro- and microelements are
excreted with sweat, especially chlorides, potassium, magnesium and that has a negative
influence on heart activity and provoke angina pectoris, cardiac infarctions incidences
especially in non-acclimated people. In order to prevent these complications salt loss
with sweating should be compensated by means of salt rich (fruit) beverages and diet
correction.
Leading specialist of tropic medicine Givoni has developed more accurate but
camber-some thermal load index calculation method. Its realization is effective if using
personal computer or calculator. Thus this method can be used only if there is a
computer at the chair. At chairs without computer the method is just introduced to
students.
4.4. Determination method and hygienic assessment of thermal load index by
Givoni.
Thermal load index allows to calculate heat amount which it is necessary to
excrete from organism through sweat evaporation in heat climate or microclimate
conditions.
This index is calculated by formula (6):
S = (M  C  R)  1/f – Enes 1/f,
(6)
where: S - thermal load index (required sweat excretion amount g/per hour);
M - metabolism intensity kcal per hour (light work- 170 kcal per hour;
medium - 300 kcal per hour, hard –420 kcal per hour);
C – heat exchange through convection, kcal per hour;
R – radiant heat amount which person gets from the Sun, kcal per hour;
Enes - required cooling swear evaporation, kcal per hour;
f - cooling sweat evaporation effectiveness.
Note. Amount of heat is added to thermal production M during calculation. This is the heat, a person
gets through convection from hot air of deserts, tropics (C) and radiation form the Sun and
locality. It should be taken away if the heat is excreted by these methods (when body’s
temperature is higher then air temperature and radiant environmental temperature).
Convection rate is calculated by the formula (7):
C = ×v0.3×(tdry -35),
(7)
where: a – coefficient which depends on clothes (see table 4.3) ;
V – air movement, m/sec;
tdry – air temperature according to dry thermometer of psychrometer.
Value of radiant temperature R is calculated by formula (8):
R  K Cl  K C  K P  In  ( I  a)  (v 0.2  0.88),
(8)
where: KCl –coefficient which depends on clothes;
KCKP –coefficient which depends on environment character and body position
according to the Sun (see table 4.4);
In – solar radiation intensity (for ordinary person at noon in the desert it is 1620
kcal per hour);
a - coefficient which depends on clothes character (see table 4);
v - air movement, m/sec.
The value l/f characterizes effectiveness of cooling by sweat excretion and is
calculated by formula (9):
1/f = е0.6  (
Е nes
 0.12 ),
Е max
(9)
where: e0.6 – 1.82;
Emax – maximal evaporative air ability, calculated by formula (10):
Еmax = ×v0.3× (42 - р),
(10)
where: β – coefficient which depends on clothes character (see table 4) ;
p - maximum air humidity, Hg mm under temperature of dry thermometer of
psychrometer;
v - air movement, m/sec.
Table 4
Coefficient values depending on clothes
Coefficient


а
КСІ
Half-dressed
person
15.8
31.6
0.35
1.0
Light summer
clothes
13.0
20.5
0.32
0.5
Light military
uniform
11.6
13.0
0.52
0.4
Table 4
Coefficients which depend on environment (KC) and human body position
according to the Sun (KP) – KCKP:
Environment
Desert
Forest
Human body position according to the Sun
Sitting back to the Sun Standing back to the Sun
0.396
0.324
0.377
0.266
Researches have confirmed the some people excrete 1 liter of sweat per hour
during 8-hour shift but not more than 12 l per 24 hours. In laboratory it has been proven,
that trained person can excrete to 2 l of sweat during 30 min but after this the person
looses working abilities. (WHO reports series # 412, 1970 ).
Excretion of 1 liter of sweat per hour in desert conditions, the heat balance can be
achieved if the heat load index will equal 600 kcal per hour with low cardio-vascular
system tension and without body temperature increase. But the same sweat excretion
intensity in high air humidity for a dressed person can be accompanied by great
thermoregulation mechanisms tension. In such conditions only 0,5 l of sweat per hour
evaporates, taking heat for latent heat of evaporation formation. (0,6 kcal per g of
sweat). The rest of sweat doesn’t evaporate and moistures the clothes.
Thermal load index (TLI) by Givony can be used for physiological tension
assessment under conditions when sweat excretion equals thermal stress. Higher TLI
can be used for physiological tension of thermoregulation mechanisms assessment.
(WHO technical report series # 412, 1970). TLI can also be used for required water
volumes to restore its reserves of the organism determination.