Medicine

TROPICAL HYGIENE A HYGIENICAL ESTIMATION OF INFLUENCING OF TROPICAL CLIMATE ON THE CONDITIONS OF LIFE, CAPACITY AND HEALTH OF POPULATION. HYGIENICAL, TOXICOLOG...

TROPICAL HYGIENE

A HYGIENICAL ESTIMATION OF INFLUENCING OF TROPICAL CLIMATE ON THE CONDITIONS OF LIFE, CAPACITY AND HEALTH OF POPULATION.

HYGIENICAL, TOXICOLOGICAL AND EPIDEMIOLOGICAL PROBLEMS OF FEED OF POPULATION OF TROPICAL REGIONS.

ORGANIZATION AND CONDUCTING OF SANITARY EXAMINATION OF FOOD PRODUCTS AND PREPARED MEAL IN THE COUNTRIES OF TORRID ZONE. METHODS OF MEDICAL CONTROL  AFTER THE FEED OF POPULATION OF COUNTRIES OF TROPICAL REGION.

Thermal interaction between the human body and the environment

In order to give a basic background of the perception of thermal comfort and the parameters that influence it, a brief description of  the  the thermal interaction between the human body and the environment (as described more extensive in ASHRAE Fundamentals, (2001)) is given.

.

The Heat Generated (M-W) is the total metabolic heat production within the body (M = metabolic rate required for the persons activity + metabolic level required for shivering) minus the energy production expended as external work done by the muscles (W). The net heat production (S) can either be stored increasing the body temperature or dissipate to the environment through the skin surface and respiratory tract.

The heat dissipation from the body to the immediate surroundings occurs by several modes of heat exchange:

  • Sensible heat flow from the skin. The sensible heat exchange from the skin surface must pass through clothing to the surrounding environment (the unit that expresses the clothing insulation is clo; 1clo = 0.155m2KW-1). These paths are treated in series and can be described in terms of heat transfer from the skin surface, through the clothing insulation to the outer clothing surface and to the environment. This heat flow is equal to the sum of convection and radiation heat transfer at the outer clothing surface. The heat losses are typically expressed in terms of environmental factors, skin temperature and skin wettedness.

  • Evaporative heat loss from the skin. The evaporative skin loss from the skin depends on the amount of moisture on the skin and the difference between the water vapour pressure at the skin and the ambient environment. It is a combination of latent heat flow from the evaporation of sweat and from the evaporation of moisture diffused through the skin.

  • Respiratory losses. According to ASHRAE Fundamentals, (2001), “During respiration the body loses both sensible and latent heat by convection and evaporation of heat and water vapour from the respiratory tract to the inhaled air. A significant amount of heat can be associated with respiration because the air is inspired at ambient conditions and expired nearly saturated at a temperature only slightly cooler than tcr (temperature of core compartment)”. Respiratory heat loss is often expresses in terms of sensible and latent heat losses.

How does the human organism lose a heat?

Major part of heat loses through the skin and mucous, other part goes on heating of food, water and breathes air. Through the skin loses main heat mass: for after one authors - 85-90%, after other - even 95%, so, only 4-6% loses on heating of food, breathe air and waters.

http://www.1cro.com/medicalphysiology/chapter21/kap%2021.htm

 

Because of that interestingly will learn how the heat is lost by skin. Appear, that skin loses a heat by three ways:

by radiation,

taking and

on evaporation of sweat moisture.

For data of Rubner, we can say, that man attached to light work in room conditions

loses by radiation about 40%,

taking - about 30% and

by evaporation - about 20% of heat.

These ciphers are directed for orientation, and really they consider vacillate dependency on conditions.

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.

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

21.03

22.06

21.09

22.12

Pole

0

23.5

0

0

Polar Circle

23.5

47.0

23.5

0

Tropics

66.5

90.0

66.5

43.0

Equator

90.0

66.5

90.0

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 00C, 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.

 

 

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.

 

 

 

METHODS OF EQUIVALENT-EFFECTIVE AND RESULTANT TEMPERATURES DETERMINATION

 

The equivalent-effective temperature (ЕЕТ) is a contingent-numeral determination of human subjective heat feeling (“comfortable”, “warm”, “cold” ect.) under different ratios of temperature, humidity, air movement, and the resultant temperature (RТ) – also the radiant temperature. These standard units of ЕЕТ and РТ correspond to temperature of still (0 m/s) 100 % water saturated air. The feeling of the heat or cold results from the different variations of these EET and RT standard units.

ЕЕТ and РТ were elaborated in special box conditions with different ratio of microclimate characteristics and drawn up in tables and nomograms.

At first, temperature, humidity, air movement are measured for EET determination in the certain room. The value of EET is determined in accordance to these data (see table 4) and an appropriate conclusion is drawn. Usage of this table is simple: ЕЕТ is determined at the intersection of air temperature value (first and last columns), air movement and humidity (at the top of the table).

The equivalent-effective temperature is determined at the intersection of dry-bulb (at the left) and wet-bulb (at the right) thermometers of the psychrometer and the air movement (m/min on the curved lines) on nomogram (see fig. 1).

Fig. 1. Nomogram of the effective temperature determination

 

The following actions should be performed to find out the resultant temperature from the nomogram (fig. 2). First, the point, where the air movement corresponds to the air temperature (by dry thermometer) is found. Then, a line starting from that point to the radiant temperature value is drawn, and from the point, where this line and the temperature scale to the right intersect, another line is drawn – to the value of the absolute air humidity (right scale). The resulting temperature value will be at the intersection of the last line and the nomogram curves.

 

air movement, m/s                                                         а

air movement, m/s                                          b

Fig. 2. Nomogram of the resultant temperature determination

(a – during light work; b – during hard work)

The example of the RT determination is shown on the fig 8.2. with dotted lines.


Table 4

 

Normal scale of the effective temperatures for the averagely dressed people during light work

 

t° in С degree

Air movement in meters per minute

t° in С degree

0

15

30

60

90

150

210

100%

50%

20%

100%

50%

20%

100%

50%

20%

100%

50%

20%

100%

50%

20%

100%

50%

20%

100%

50%

20%

0

0

0.9

1.3

0.9

0.4

0

1

1

1.8

2.1

0.8

0.1

0.4

0.0

1

2

2

2.7

3.0

0.3

1.0

1.4

0.5

0.0

2

3

3

3.7

3.9

1.3

2.0

2.3

0.3

0.5

0.9

3

4

4

4.5

4.7

2.4

3.0

3.2

0.8

1.7

1.9

0.7

1.0

0.5

4

5

5

5.4

5.5

3.4

4.0

4.1

1.9

2.6

2.9

0.4

0.1

0.5

1.0

5

6

6

6.2

6.3

4.5

4.9

5.1

3.0

3.6

3.9

1.6

1.2

1.6

0.5

1.0

6

7

7

7.1

7.1

5.5

5.8

5.9

4.2

4.6

4.7

2.9

2.3

2.8

0.3

0.5

1.1

7

8

8

7.9

7.9

6.6

6.9

6.9

5.3

5.7

5.8

4.2

3.5

3.9

1.0

1.9

2.2

0.2

0.3

0.8

8

9

9

8.8

8.7

7.7

7.7

7.7

6.4

6.8

6.8

5.4

4.5

4.9

2.2

2.9

3.3

0.2

1.0

1.4

0.3

0.3

9

10

10

9.7

9.6

8.8

8.7

8.7

7.6

7.7

7.7

6.6

5.7

5.8

3.5

4.2

4.4

1.1

2.1

2.5

0.6

0.9

1.5

10

11

11

10.5

10.3

9.9

9.6

9.4

8.8

8.8

8.8

7.9

6.8

6.9

4.9

5.3

5.5

2.4

3.3

3.6

0.9

2.2

2.8

11

12

12

11.3

11.1

10.8

10.5

10.2

9.9

9.6

9.4

9.1

8.0

8.0

6.1

6.3

6.4

3.9

4.5

4.6

2.2

3.3

3.9

12

13

13

12.1

11.8

12.0

11.4

11.1

11.0

10.5

10.3

10.3

8.9

8.9

7.3

7.4

7.4

5.2

5.7

5.9

3.6

4.5

5.0

13

14

14

13.0

12.5

13.1

12.3

11.9

12.1

11.5

11.2

11.5

10.0

9.7

8.6

8.5

8.4

6.6

6.9

7.0

5.1

5.8

6.1

14

15

15

13.9

13.3

14.1

13.2

12.8

13.1

12.4

12.0

12.7

11.0

10.6

10.0

9.8

9.5

8.0

8.1

8.1

6.6

7.0

7.2

15

16

16

14.7

14.1

15.2

14.1

13.5

14.3

13.4

12.8

13.9

12.0

11.6

11.3

10.7

10.5

9.4

9.1

9.1

8.0

8.2

8.3

16

17

17

15.5

14.8

16.2

15.0

14.2

15.3

14.3

13.6

15.1

13.0

12.5

12.5

11.7

11.4

10.8

10.2

10.1

9.5

9.5

9.4

17

18

18

16.3

15.5

17.3

15.7

15.0

16.4

15.2

14.4

16.2

14.0

13.3

13.7

12.7

12.4

11.9

11.3

11.1

10.8

10.5

10.4

18

19

19

17.2

16.3

18.4

16.6

15.7

17.5

16.1

15.3

17.4

14.9

14.2

15.0

13.8

13.4

13.3

12.4

12.1

12.2

11.7

11.4

19

20

20

18.0

17.0

19.4

17.4

16.5

18.7

17.0

16.0

18.5

15.9

15.1

16.2

14.8

14.4

14.6

13.5

13.1

13.5

12.9

12.4

20

21

21

18.8

17.7

20.4

18.3

17.2

19.8

17.8

16.7

19.6

16.7

15.8

17.4

15.9

15.1

16.0

14.6

14.1

14.9

13.9

13.4

21

22

22

19.5

18.3

21.4

19.1

18.0

20.9

18.6

17.5

20.9

17.6

16.7

18.6

16.9

16.0

17.2

15.6

15.0

16.2

15.0

14.4

22

23

23

20.3

19.0

22.5

19.9

18.5

21.9

19.4

18.3

22.0

18.6

17.5

19.9

17.9

16.7

18.3

16.6

15.9

17.5

16.1

15.3

23

24

24

21.1

19.7

23.5

20.6

19.3

23.0

20.3

19.0

23.1

19.5

18.3

21.1

18.8

17.6

19.6

17.8

16.8

18.8

17.1

16.2

24

25

25

22.0

20.4

24.5

21.5

20.0

24.0

21.2

19.6

24.2

20.5

19.0

22.3

19.6

18.5

21.0

18.8

17.8

20.0

18.1

17.2

25

26

26

22.8

21.2

25.5

22.3

20.7

25.1

22.0

20.4

25.3

21.2

19.8

23.4

20.6

19.3

22.1

19.7

18.5

21.2

19.1

18.0

26

27

27

23.5

21.8

26.6

23.0

21.3

26.1

22.8

21.1

26.5

22.0

20.5

24.5

21.5

20.1

23.4

20.8

19.4

22.5

20.1

18.8

27

28

28

24.2

22.5

27.6

23.9

22.0

27.2

23.5

21.8

27.8

22.9

21.2

25.7

22.4

20.8

24.5

21.6

20.2

23.6

21.0

19.8

28

29

29

25.0

23.1

28.6

24.6

22.6

28.2

24.3

22.4

28.8

23.6

21.9

26.8

23.3

21.5

25.9

22.5

21.0

24.9

21.9

20.5

29

30

30

25.8

23.6

29.6

25.4

23.6

29.3

25.2

23.1

29.8

24.5

22.5

28.1

24.1

22.2

27.1

23.4

21.7

26.3

22.8

20.9

30

31

31

26.5

24.2

30.8

26.2

23.9

30.3

25.9

23.6

30.8

25.3

23.3

29.2

25.0

22.9

28.2

24.3

22.5

27.5

23.8

22.1

31

32

32

27.2

24.6

31.7

27.0

24.5

31.4

26.7

24.2

32.1

26.2

23.9

30.3

25.8

23.6

29.4

25.1

23.2

28.8

24.6

22.9

32

33

33

28.0

25.2

32.8

27.8

25.1

32.4

27.4

24.9

33.2

27.0

24.5

31.5

26.5

24.2

30.6

26.0

23.9

30.2

25.5

23.5

33

34

34

28.6

25.9

33.9

28.4

25.6

33.5

28.3

25.4

34.5

27.6

25.1

32.8

27.3

24.9

32.2

26.7

24.5

31.6

26.4

24.2

34

35

35

29.5

26.4

34.8

29.1

26.2

34.6

28.9

26.0

35.5

28.4

25.8

34.0

28.1

25.4

33.5

27.5

25.2

33.1

27.2

24.9

35

36

36

30.1

27.0

35.9

29.9

26.8

35.8

29.5

26.3

36.8

29.2

26.3

35.3

28.8

26.1

35.0

28.3

25.8

34.6

28.0

25.5

36

37

37

30.7

27.4

37.0

30.5

27.3

36.9

30.3

26.9

38.0

29.9

26.9

36.6

29.6

26.7

36.5

29.1

26.4

36.4

28.9

26.2

37

38

38

31.4

28.1

38.0

31.2

27.9

38.0

31.0

27.4

39.2

30.6

27.4

38.0

30.3

27.3

38.1

29.9

27.0

29.5

26.8

38

39

39

32.1

28.6

39.0

32.0

28.4

39.1

31.7

28.0

40.4

31.4

28.0

39.4

31.1

27.9

39.9

30.6

27.5

30.4

27.3

39

40

40

32.8

29.1

40.0

32.7

28.9

40.2

32.4

28.5

41.6

32.1

28.5

40.7

31.9

28.3

41.4

31.4

28.1

31.2

27.9

40

41

41

33.4

29.6

41.1

33.3

29.3

33.1

29.3

32.8

29.0

42.2

32.6

28.9

32.2

28.8

32.0

28.4

41

42

42

34.1

30.1

34.0

29.9

33.8

29.8

33.5

29.5

33.3

29.4

33.0

29.1

32.1

29.0

42

43

43

34.9

30.5

34.8

30.3

34.5

30.3

34.2

30.1

34.1

30.0

33.8

29.6

33.7

29.4

43

44

44

35.5

31.0

35.4

30.9

35.2

30.9

35.1

30.5

35.0

30.4

34.6

30.1

34.5

30.0

44

45

45

36.2

31.4

36.1

31.3

36.0

31.3

36.0

31.0

35.8

30.9

35.4

30.6

35.3

30.5

45

46

46

36.9

31.9

36.9

31.9

36.7

31.6

36.7

31.4

36.5

31.3

36.3

31.1

36.2

31.0

46

47

47

37.6

32.3

37.6

32.2

37.5

32.2

37.5

32.0

37.4

31.8

37.3

31.6

37.2

31.4

47

48

48

38.4

32.8

38.4

32.7

38.3

32.6

38.3

32.4

38.3

32.3

38.3

32.1

38.3

32.0

48

49

49

39.2

33.2

39.2

33.2

39.1

33.1

39.2

32.9

39.2

32.8

40.0

32.7

39.5

32.4

49

50

50

39.9

33.6

40.0

33.5

40.0

33.5

40.0

33.3

40.3

33.2

40.6

33.1

32.9

50

 

Comment. Relative air humidity is shown in percentage.

 

Methods of the assessment of human heat balance by calculation of heat emission

 

the assessment of human feeling of the heat/cold is performed comparing the heat production during work and heat emission. heat emission is calculated as a sum of the irradiation, conduction and water evaporation.

The basic data are:

a) the human heat production in a calm state accounts to 0.8 – 1.5 kcal (3.34 – 6.27 kj) per 1 kg body weight per 1 hour, during hard work – 7-9 kcal/kg×h;

b) the body surface of “average” human (170 cm of height and 65 kg of body weight) is approximately 1.8 m2 (see table 5);

c) 100% of the body surface takes part in heat emission by conduction and sweat evaporation;

d) 80% of the body surface takes part in heat emission by irradiation (see table 5).

40 % of the body surface takes part in heat emission by irradiation relating to the one-sided heat radiation source.

Table 5

Dependence of the human body surface on body weight

Body weight, kg

Body surface, m2

100 %

80 %

40

1.323

1.058

45

1.482

1.186

50

1.535

1.228

55

1.635

1.308

60

1.729

1.383

65

1.830

1.464

70

1.922

1.538

75

2.008

1.606

80

2.098

1.678

85

2.188

1.750

90

2.263

1.810

95

2.338

1.870

100

2.413

1.930

 

1. heat emission by irradiation (radiation) can be calculated using the following formula:

qirr. = 4.5×(т1 – т2) s

(1)

where: q – heat emitted by irradiation, kcal/h;

  т1 – body temperature, °с;

  т2 – internal wall surface temperature, °с;

  s – body surface area, m2.

 

2. Heat emission by conduction can be calculated using the following formula:

qcon = 6(т1 – т2) × (0.5 + √‾v) s

(2.1)

qcon = 7.2 (т1 – т2) × (0.27 + √‾v)s

(2.2)

where : q – heat emitted by conduction, kcal/h;

   6; 0.5 – constant coefficients if air movement is less than 0.6 m/s;

   т1 – body temperature, °с;

   т2 – air temperature, °с;

   7.2; 0.27 – constant coefficients if air movement is higher than 0.6 m/s;

   v – air movement, m/s;

   s – body surface area, m2.

 

3. The maximum amount of water evaporated from the body surface can be calculated using the following formula:

рevap = 15(fmax  fabs) × (0.5 +√‾v)s

(3.1)

where: рevap – water. evaporated from body surface under this conditions, ml/h;

15 – constant coefficient;

fmax – maximum humidity under skin temperature of the body;

fabs – absolute humidity under currant air temperature.

“fabs” – can be calculated using the following formula:

(3.2)

where: f max– maximum humidity under air temperature, hg mm. ;

 frel.– relative humidity under current air temperature, %;

 (fmax  fabs) – physiological humidity deficit, hg mm.;

 vair movement, m/s;

 s body surface area, m2.

Quantity of emitted heat may be calculated by multiplication of the result by 0.6 (calorie evaporating coefficient of 1 g of water). or by putting the coefficient “9” in formula (3.1) instead of “15” (0.6×15 = 9). it is necessary to remember that an adequate heat self-feeling remains stable if sweat evaporation is not more than 250 ml (it takes 150 kcal).

 

Example of the calculation:

a “standard men” (body surface is 1.8 m2, height – 170 cm, body weight – 65 kg) in light clothing with body temperature of 360c works physically hard (570 kcal/h) in a room. microclimate characteristics of the room are: air temperature 320c, average radiant temperature 220c, air movement 0.7 m/sec., relative humidity 70%. evaluate the feeling of this man. estimate the heat emission by irradiation (heat emission from 80% body surface) and conduction using the formula (1)

qirr = 4.5(36-22)×1.8×0.8 = 90.72 kcal/h

qcond = 7.2×(36-22)×(0.27 + 0.83)×1.46 = 160 kcal/h

For calculation of the maximum amount of water evaporated from body surface, the maximum humidity under 36° с is determined according to table “maximum pressure of water vapour at different temperatures”. maximum humidity is 42.2 hg mm according to this table.

Absolute humidity under the air temperature 32° с is determined using the formula (3.2):

fаbs. =  = 29.5 hg mm

insert the calculation results into the formula (3.1):

рevap =15× (42.2 – 29.5)×(0.5 = 0.83)×1.8 = 456 ml/h.

heat emission by evaporation under this condition is:

456×0.6 = 273.6 kcal/h.

calculate the total heat emission:

q = 90. 72 + 160.0 + 273.6 = 524.32 kcal.

Comparing the heat emission and heat production (570 kcal/h) for the assessment of the feelings of the human, we can conclude, that the heat production exceeds the heat emission, and thus the microclimate of this room causes the “heating”.

Comment: these calculations ignore heat emission by breathing: inhaled air heating and water evaporation from lung surface. this amount is near 15% of total heat emission in comfortable conditions. we inhale the air of certain temperature and humidity. an exhaled air is heated to the body temperature and is saturated to the 100% humidity.

Heat exchange and thermal regulation peculiarities of the organism in tropic climate

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.

Hygienic standards and calculation methods of heat load of organism in hot and tropic climate conditions

 

Maximum allowable equivalent-effective temperature (EET) indices.

 

Table 2

 

Labour mode

Labour intensity

light

medium

hard

Without breaks during the shift

30.4

28.9

26.1

With breaks:

 

 

 

-every 3 hours

32.7

29.9

27.6

-every 2 hours

33.3

31.0

29.9

-every 1 hour

35.0

32.7

30.4

-every 30 min

38.2

35.5

34.4

- every 20 min

40.5

37.7

35.0

For people acclimatized to high temperature

32.2

29.4

28.9

For non-acclimatized to high temperature people

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

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

v0.6

0.17

0.25

0.38

0.49

0.58

0.66

0.74

0.81

0.87

0.94

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 = α×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):

,      (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 * (),                        (9)

where:  e0.6 – 1.82;

   Emax – maximal evaporative air ability, calculated by formula (10):

Еmax = β ×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

Half-dressed person

Light summer clothes

Light military uniform

15.8

13.0

11.6

31.6

20.5

13.0

а

0.35

0.32

0.52

КСІ

1.0

0.5

0.4

 

Table 4

 

Coefficients which depend on environment (KC) and human body position according to the Sun (KP) – KCKP:

 

Environment

Human body position according to the Sun

Sitting back to the Sun

Standing back to the Sun

Desert

0.396

0.324

Forest

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.

 

HEAT TRANSFER,

 in physics, process by which energy in the form of heat is exchanged between bodies or parts of the same body at different temperatures. Heat is generally transferred by convection, radiation, or conduction. Although these three processes can occur simultaneously, it is not unusual for one mechanism to overshadow the other two. Heat, for example, is transferred by conduction through the brick wall of a house, the surfaces of high-speed aircraft are heated by convection, and the earth receives heat from the sun by radiation.

Heat Transfer Heat can be transferred by three processes: conduction, convection, and radiation. Conduction is the transfer of heat along a solid object; it is this process that makes the handle of a poker hot, even if only the tip is in the fireplace. Convection transfers heat through the exchange of hot and cold molecules; this is the process through which water in a kettle becomes uniformly hot even though only the bottom of the kettle contacts the flame. Radiation is the transfer of heat via electromagnetic (usually infrared) radiation; this is the principal mechanism through which a fireplace warms a room.© Microsoft Corporation. All Rights Reserved. 

CONDUCTION

This is the only method of heat transfer in opaque solids. If the temperature at one end of a metal rod is raised by heating, heat is conducted to the colder end, but the exact mechanism of heat conduction in solids is not entirely understood. It is believed, however, to be partially due to the motion of free electrons in the solid matter, which transport energy if a temperature difference is applied. This theory helps to explain why good electrical conductors also tend to be good heat conductors (see Conductor, Electrical). Although the phenomenon of heat conduction had been observed for centuries, it was not until 1882 that the French mathematician Jean Baptiste Joseph Fourier gave it precise mathematical expression in what is now regarded as Fourier's law of heat conduction. This physical law states that the rate at which heat is conducted through a body per unit cross-sectional area is proportional to the negative of the temperature gradient existing in the body.

The proportionality factor is called the thermal conductivity of the material. Materials such as gold, silver, and copper have high thermal conductivities and conduct heat readily, but materials such as glass and asbestos have values of thermal conductivity hundreds and thousands of times smaller, conduct heat poorly, and are referred to as insulators (see Insulation). In engineering applications it is frequently necessary to establish the rate at which heat will be conducted through a solid if a known temperature difference exists across the solid. Sophisticated mathematical techniques are required to establish this, especially if the process varies with time, the phenomenon being known as transient-heat conduction. With the aid of analog and digital computers, these problems are now being solved for bodies of complex geometry.

CONVECTION

Conduction occurs not only within a body but also between two bodies if they are brought into contact, and if one of the substances is a liquid or a gas, then fluid motion will almost certainly occur. This process of conduction between a solid surface and a moving liquid or gas is called convection. The motion of the fluid may be natural or forced. If a liquid or gas is heated, its mass per unit volume generally decreases. If the liquid or gas is in a gravitational field, the hotter, lighter fluid rises while the colder, heavier fluid sinks. This kind of motion, due solely to nonuniformity of fluid temperature in the presence of a gravitational field, is called natural convection. Forced convection is achieved by subjecting the fluid to a pressure gradient and thereby forcing motion to occur according to the law of fluid mechanics.

If, for example, water in a pan is heated from below, the liquid closest to the bottom expands and its density decreases; the hot water as a result rises to the top and some of the cooler fluid descends toward the bottom, thus setting up a circulatory motion. Similarly, in a vertical gas-filled chamber, such as the air space between two window panes in a double-glazed, or Thermopane, window, the air near the cold outer pane will move down and the air near the inner, warmer pane will rise, leading to a circulatory motion.

The heating of a room by a radiator depends less on radiation than on natural convection currents, the hot air rising upward along the wall and cooler air coming back to the radiator from the side of the bottom. Because of the tendencies of hot air to rise and of cool air to sink, radiators should be placed near the floor and air-conditioning outlets near the ceiling for maximum efficiency. Natural convection is also responsible for the rising of the hot water and steam in natural-convection boilers (see Boiler) and for the draft in a chimney. Convection also determines the movement of large air masses above the earth, the action of the winds, rainfall, ocean currents, and the transfer of heat from the interior of the sun to its surface.

RADIATION

Wilhelm Wien German physicist Wilhelm Wien won the 1911 Nobel Prize in physics. His discoveries in the field of radiation, including the laws that govern heat radiation, laid the foundation for the development of the quantum theory.© The Nobel Foundation 

 This process is fundamentally different from both conduction and convection in that the substances exchanging heat need not be in contact with each other. They can, in fact, be separated by a vacuum. Radiation is a term generally applied to all kinds of electromagnetic-wave phenomena. Some radiation phenomena can be described in terms of wave theory (see Wave Motion), and others can be explained in terms of quantum theory. Neither theory, however, completely explains all experimental observations. The German-born American physicist Albert Einstein conclusively demonstrated (1905) the quantized behavior of radiant energy in his classical photoelectric experiments. Before Einstein's experiments the quantized nature of radiant energy had been postulated, and the German physicist Max Planck used quantum theory and the mathematical formalism of statistical mechanics to derive (1900) a fundamental law of radiation (see Statistics). The mathematical expression of this law, called Planck's distribution, relates the intensity or strength of radiant energy emitted by a body to the temperature of the body and the wavelength of radiation. This is the maximum amount of radiant energy that can be emitted by a body at a particular temperature. Only an ideal body (blackbody,) emits such radiation according to Planck's law. Real bodies emit at a somewhat reduced intensity. The contribution of all frequencies to the radiant energy emitted by a body is called the emissive power of the body, the amount of energy emitted by a unit surface area of a body per unit of time. As can be shown from Planck's law, the emissive power of a surface is proportional to the fourth power of the absolute temperature. The proportionality factor is called the Stefan-Boltzmann constant after two Austrian physicists, Joseph Stefan and Ludwig Boltzmann, who, in 1879 and 1884, respectively, discovered the fourth power relationship for the emissive power. According to Planck's law, all substances emit radiant energy merely by virtue of having a positive absolute temperature. The higher the temperature, the greater the amount of energy emitted. In addition to emitting, all substances are capable of absorbing radiation. Thus, although an ice cube is continuously emitting radiant energy, it will melt if an incandescent lamp is focused on it because it will be absorbing a greater amount of heat than it is emitting.

Opaque surfaces can absorb or reflect incident radiation. Generally, dull, rough surfaces absorb more heat than bright, polished surfaces, and bright surfaces reflect more radiant energy than dull surfaces. In addition, good absorbers are also good emitters; good reflectors, or poor absorbers, are poor emitters. Thus, cooking utensils generally have dull bottoms for good absorption and polished sides for minimum emission to maximize the net heat transfer into the contents of the pot. Some substances, such as gases and glass, are capable of transmitting large amounts of radiation. It is experimentally observed that the absorbing, reflecting, and transmitting properties of a substance depend upon the wavelength of the incident radiation. Glass, for example, transmits large amounts of short wavelength (ultraviolet) radiation, but is a poor transmitter of long wavelength (infrared) radiation. A consequence of Planck's distribution is that the wavelength at which the maximum amount of radiant energy is emitted by a body decreases as the temperature increases. Wien's displacement law, named after the German physicist Wilhelm Wien, is a mathematical expression of this observation and states that the wavelength of maximum energy, expressed in micrometers (millionths of a meter), multiplied by the Kelvin temperature of the body is equal to a constant, 2878. Most of the energy radiated by the sun, therefore, is characterized by small wavelengths. This fact, together with the transmitting properties of glass mentioned above, explains the greenhouse effect. Radiant energy from the sun is transmitted through the glass and enters the greenhouse. The energy emitted by the contents of the greenhouse, however, which emit primarily at infrared wavelengths, is not transmitted out through the glass. Thus, although the air temperature outside the greenhouse may be low, the temperature inside the greenhouse will be much higher because there is a sizable net heat transfer into it.

In addition to heat transfer processes that result in raising or lowering temperatures of the participating bodies, heat transfer can also produce phase changes such as the melting of ice or the boiling of water. In engineering, heat transfer processes are usually designed to take advantage of these phenomena. In the case of space capsules reentering the atmosphere of the earth at very high speed, a heat shield that melts in a prescribed manner by the process called ablation is provided to prevent overheating of the interior of the capsule. Essentially, the frictional heating produced by the atmosphere is used to melt the heat shield and not to raise the temperature of the capsule (see Friction).

What is the heat losing way by radiation?

From physics we know, that any more heated body radiates more heat, than less heated. So, even not colliding with it, it gives to it its heat, while the temperatures of both bodies will not complete with each other.

Man in room conditions is usually circled by objects with more low temperature, than his body, that is why takes place heat losing by radiation.

•Also heat is lost by installation. In this case a heat is lost by two ways - conduction and convection.

Conduction is a heat transition on the strength of contiguity of objects, and also air parts from more heated to less heated. Convection is a heat transmission on the strength of mediators - air, steam, liquid, the fractions of which, heating attached to contact with more warm body, bear off heat and return it attached to contiguity with more cold objects. On the strength of temperature difference in intermediate environment, for example, in air, the convectional streams are generated.

The third way of heat losing is evaporation of moisture.

A human skin is always covered by sweat, water of which evaporates. For this process it is necessary expenditure of warm /secretive evaporation temperature /.

http://ppo.tamuk.edu/ehs/Heat_Stress/heatstress.htm

 

HEAT DISORDERS

http://www.answers.com/topic/heat-disorders

Heat disorder results from unaccustomed or prolonged exposure to excessive heat causing the body's cooling mechanism to break down leading to damages to the body's heat regulating mechanism. Heat exhaustion and heat stroke are similar problems, but they are not the same. Heat exhaustion refers to overheating of the body due to excessive loss of fluids or in rare cases salt depletion. Heat stroke, a more severe condition that occurs when the body's thermoregulatory system stops working. Heat exhaustion is not fatal but heat stroke can be and can bring about an irreversible coma and even death.

A heat disorder results when a person engages in physical activity to the extent where the heat production within his body exceeds its ability to lose heat adequately. This results in a rise in inner body (body core) temperature to the levels at which normal body functions are interfered with. This may lead to temporary or permanent disturbances in bodily functions.

CAUSES AND THE RISK FACTORS?

Heat disorder is due to unaccustomed or prolonged exposure to excessive heat. It is more common in hot climates and results from excessive sweating, leading to loss of fluids and salts and disturbances of the electrolyte balance in the body fluids. Many of the symptoms are the same as for heat exhaustion. However, cessation of sweating, difficulty walking, disorientation, fainting or unconsciousness indicates heat stroke. The key symptom to look for is disorientation. The risk increases with inter current illnesses, such as gastrointestinal disorders where there has been a vomiting and diarrhoea. Any illness such as diabetes may make this condition more likely to occur and elderly people should be especially careful.

KNOW THE DIFFERENCE

It's important to note the differences between the three main heat related disorders. While heat cramps can be uncomfortable, they are not life threatening. Heat stroke on the other hands needs immediate medical attention. When it comes to heat, your body is like a car. If either one overheats, it can cause minor or major problems. But knowing what to do can help your body (or your car for that matter) to keep running. When a person has heat stroke, it's like a car running with almost all the water boiled out of the radiator. It's very serious, and can lead suddenly and without warning to a complete breakdown. Learn to recognize the symptoms and treat the problem accordingly.

Heat cramps - are associated with lack of fluids, high temperature, excessive salt and fluid losses due to profuse sweating when the bodies attempt to rapidly lose heat. Feeling most like a severe muscle pull, heat cramps are forceful and painful. Heat cramps, while painful, is not life threatening. It presents as intermittent muscle contractions in both the gastronomes or hamstring area (back of calves). 

Heat exhaustion - a more severe condition caused by extreme body heat. Excessive heat and dehydration can cause the body to overreact, thus raising your body temperature to over 39OC. Heat exhaustion is a serious condition and should be carefully monitored. 

Symptoms includes:

  • Paleness, cool, clammy skin

  • Profuse sweating with an elevated body temperature

  • Extreme fatigue

  • Dizziness, lightheadedness

  • Nausea, vomiting

  • Fainting

  • Muscle cramps in the limbs, abdomen or back

  • Rapid, shallow breathing

Heat stroke - is the most dangerous heat related disorder, often putting victim's lives in danger. Heat stroke is a medical emergency, anyone exhibiting the signs and symptoms should be rushed to the nearest medical facility. Heat stroke does not have to be caused by exercise or exertion. High temperatures, lack of body fluids and overexposure to the elements can all bring about heat stroke. It manifests with a body core temperature of 41OC and above.

SYMPTOMS

The key symptom to look for is disorientation. A person who is functioning well mentally isn't in danger. Someone who's "jelly brained" is in trouble and will be too disoriented to help themselves. Many of the symptoms are the same as for heat exhaustion; however, cessation of sweating, difficulty walking, disorientation, fainting or unconsciousness indicates heatstroke. The first sign to look for in a victim is red, hot, flushed skin. When the body overheats, it can go into crisis. Usually we sweat when we're hot, but when someone has heat stroke; there is no sweat, so it is critical that they receive emergency care immediately to relieve their body of heat. 

Other signs of Heat stroke include:

  • Restlessness

  • Anxiety, confusion, aggressive behaviour

  • Red, swollen eyes

  • The pulse rate increases rapidly and may reach 160.

  • Fast rise in body temperature above 41OC when sweating stops and the patient feels as if burning up.

  • Loss of consciousness. Survivors are likely to have permanent brain damage.

Table 1Classification, medical aspects and prevention of heat illness (from (6)).

Category and clinical features

Predisposing factors

Underlying physiological disturbance

Treatment

Prevention

1. Temperature regulation heatstroke

Heatstroke: (1) hot dry skin usually red, mottled or cyanotic; (2) t re, 40.5C (104F) and over; (3) confusion, loss of consciousness, convulsions, t re continues to rise; fatal if treatment delayed

(1) Sustained exertion in heat by unacclimatised workers; (2) lack of physical fitness and obesity; (3) recent alcohol intake; (4) dehydration; (5) individual susceptibility; and (6) chronic cardiovascular disease

Failure of the central drive for sweating (cause unknown) leading to loss of evaporative cooling and an uncontrolled accelerating rise in t re, there may be partial rather than complete failure of sweating

Immediate and rapid cooling by immersion in chilled water with massage or by wrapping in wet sheet with vigorous fanning with cool dry air, avoid overcooling, treat shock if present

Medical screening of workers, selection based on health and physical fitness, acclimatisation for 5–7 days by graded work and heat exposure, monitoring workers during sustained work in severe heat

 

 

 

 

 

2. Circulatory hypostasis heat syncope

Fainting while standing erect and immobile in heat

Lack of acclimatisation

Pooling of blood in dilated vessels of skin and lower parts of body

Remove to cooler area, rest recumbent position, recovery prompt and complete

Acclimatisation, intermittent activity to assist venous return to the heart

 

 

 

 

 

3. Water and/or salt depletion

(a) Heat exhaustion

(1) Fatigue, nausea, headache and giddiness; (2) skin clammy and moist; complexion pale, muddy or hectic flush; (3) may faint on standing with rapid thready pulse and low blood pressure; (4) oral temperature normal or low but rectal temperature usually elevated (37.5–38.50C) (99.5–101.30F); water restriction type; urine volume small, highly concentrated; salt restriction type; urine less concentrated, chlorides less than 3 g/L

(1) Sustained exertion in heat; (2) lack of acclimatisation; and (3) failure to replace water lost in sweat

(1) Dehydration from deficiency of water; (2) depletion of circulating blood volume; (3) circulatory strain from competing demands for blood flow to skin and to active muscles

Remove to cooler environment, rest recumbent position, administer fluids by mouth, keep at rest until urine volume indicates that water balances have been restored

Acclimatise workers using a breaking-in schedule for 5–7 days, supplement dietary salt only during acclimatisation, ample drinking water to be available at all times and to be taken frequently during work day

 

 

 

 

 

(b) Heat cramps

Painful spasms of muscles used during work (arms, legs or abdominal); onset during or after work hours

(1) Heavy sweating during hot work; (2) drinking large volumes of water without replacing salt loss

Loss of body salt in sweat, water intake dilutes electrolytes, water enters muscles, causing spasm

Salted liquids by mouth or more prompt relief by I-V infusion

Adequate salt intake with meals; in unacclimatised workers supplement salt intake at meals

 

 

 

 

 

4. Skin eruptions

(a) Heat rash (miliaria rubra; ‘prickly heat’)

Profuse tiny raised red vesicles (blister-like) on affected areas, pricking sensations during heat exposure

Unrelieved exposure to humid heat with skin continuously wet with unevaporated sweat

Plugging of sweat gland ducts with retention of sweat and inflammatory reaction

Mild drying lotions, skin cleanliness to prevent infection

Cool sleeping quarters to allow skin to dry between heat exposures

 

 

 

 

 

(b) Anhydrotic heat exhaustion (miliaria profunda)

Extensive areas of skin which do not sweat on heat exposure, but present gooseflesh appearance, which subsides with cool environments; associated with incapacitation in heat

Weeks or months of constant exposure to climatic heat with previous history of extensive heat rash and sunburn

Skin trauma (heat rash; sunburn) causes sweat retention deep in skin, reduced evaporative cooling causes heat intolerance

No effective treatment available for anhydrotic areas of skin, recovery of sweating occurs gradually in return to cooler climate

Treat heat rash and avoid further skin trauma by sunburn, periodic relief from sustained heat

 

 

 

 

 

5. Behavioural disorders

(a) Heat fatigue – transient

Impaired performance of skilled sensorimotor, mental or vigilance tasks, in heat

Performance decrement greater in unacclimatised and unskilled worker

Discomfort and physiologic strain

Not indicated unless accompanied by other heat illness

Acclimatisation and training for work in the heat

 

 

 

 

 

(b) Heat fatigue – chronic

Reduced performance capacity, lowering of self-imposed standards of social behaviour (e.g. alcoholic over-indulgence), inability to concentrate, etc.

Workers at risk come from temperate climates, for long residence in tropical latitudes

Psychosocial stresses probably as important as heat stress, may involve hormonal imbalance but no positive evidence

Medical treatment for serious cases, speedy relief of symptoms on returning home

Orientation on life in hot regions (customs, climate, living conditions, etc.)

 

http://www.globalhealthaction.net/index.php/gha/article/view/2057/2538

 

PREVENTION

It is possible to avoid suffering the ill effects of heat related disorders by taking a few simple precautions. Heat related disorders are preventable. Like many sicknesses, it's easier to take steps against it than it is to treat it. 

Acclimatisation
Acclimatisation is the ability of the body to undergo physiological adaptations so that the individual is able to cope better with the environmental and physiological heat stress. 

Hydration
The easiest way to avoid Heat stroke and other heat disorders is to keep your body well hydrated. This means drinking plenty of water before, during and after exposure to the elements. Drink, drink, drink, eight or more glasses of water a day during normal weather conditions and twice that during high heat periods and exercising or working in hot conditions. 

Clothing
What you wear can play a big factor in how your body will handle the heat. Excessive and tight clothing can contribute to dehydration by impeding evaporation of sweat. This causes the body to produce more sweat in order to cool the body and also leads to rise in body temperature. Light colored, loose fitting clothing will aid your body in breathing and cooling itself down naturally. Tight clothing restricts such a process and dark colors absorb the sun's light and heat. 

Limit Yourself
Watching how much activity you're participating in during hottest part of the days is also important. Heat stroke can set in less than an hour. If you feel yourself getting warm or lightheaded, it's best to take a time out and rest in the shade. Try to schedule your runs during the cooler hours of the day - morning or early evening.

6 DO'S FOR PREVENTION OF HEAT DISORDERS

  • Do drink water until you are no longer thirsty and then a little more. Takes frequent breaks and drink plenty of cool water. Even when you're not thirsty, your body is losing fluid, which needs to be replaced.

  • Do rest well before and in between strenuous exercises.

  • Do loosen your clothing while resting.

  • Do report sick if you are not feeling well before, after or during strenuous exercises or activities

  • Do avoid exercises if medical leave is granted.

  • Do remember the 7 R's of the first aid for heat disorders.

WHAT YOU CAN DO
7 R MANAGEMENT

  • Recognise early signs and symptoms of heat related illness.

  • Rest the victim in cool, shady environment preferably into an air-conditioned building.

  • Remove all clothing to cool the body, if possible; soak the person in a cool bath.

  • Resuscitate with CPR, if victim is unconscious. Contact an ambulance right away.

  • Reduce the victim's body temperature as fast as possible by applying a wet towel around neck, armpit and groin or splash water on his body and fan him or her.

  • Re-hydrate the victim if he is conscious, by giving plenty of fluids, taking it slowly rather than gulping it down.

  • Rush the victim to the nearest medical facility. Prompt treatment is necessary to prevent rapid deterioration into coma or death.

WHAT YOUR DOCTOR CAN DO

  • Treat severe heatstroke with rapid cooling by immersion in ice water /used of Body Cooling Unit (BCU) a special equipment that dispenses continuous fine sprays of water until the body temperature drops below 38OC, followed by cooling with cold wet towels under a fan.

  • Give intravenous fluids to correct the salt and water balance in the body.

http://www.nmsu.edu/safety/programs/industrial_safety/heatstress_intro.htm

http://healthmagazine.ae/heat-disorders-or-heat-related-illness/

NUTRITION IN TROPICAL COUNTRY

INTRODUCTION

In the developing areas of the world, some of the greatest health problems are directly related to inadequate nutrition. These include early childhood malnutrition due to calorie-protein deficiencies as well as iodine deficiency goiter, blind­ness due to lack of vitamin A, and a host of infectious diseases made worse by poor nutrition.

Iron-deficiency anemia and dental caries, widespread disorders related to malnutrition, have neither geographic nor socioeconomic boundaries. Even in highly developed societies there may be large segments of the population in which hunger and undernutrition impair physical and men­tal performance.

Nutrition is the science of food, the materials or nutrients in food, what they do and how they interact — all in relation to health. Nutrition comes from food, good food that one enjoys (for eating has always been one of the pleasures of life), from food in variety so as to supply the more than 50 known nutri­ents that are necessary for proper nutrition, thereby providing the best of health that one's genetic or hereditary background permits.

Nutrition as a science can be regarded as the study of six main categories of food components: protein, carbohydrate, fat, minerals, vitamins, and water. The first three categories - protein, carbohydrate, and fat — are the only ones that provide calories. Protein provides 4 Calories/gm, as does carbohydrate. Fat provides slightly more than twice as much— 9 Calories/gm.

Although minerals and vitamins provide no calories, they function in the many metabolic processes whereby one obtains and utilizes energy from foods and builds and then maintains body tissues. Minerals also function as vital constituents of many body tissues. Iron is a necessary component of hemo­globin, myoglobin, and the cytochromes, and calcium and fluoride are required for sound teeth and bones.

Nutrition is important in modern health and medicine — in improving and maintaining good health and in improving poor health.

The acute and severe vitamin deficiencies as manifested by the classical nutritional diseases — scurvy, pellagra, beri­beri, and xerophthalmia are prevalent in many other parts of the world.

Rational nutrition and its provision in tropical regions

Rational nutrition and its provision in arid and humid areas with tropical climate is considered according to abovementioned natural peculiarities, social development of the countries, natural resources presence, which allow to solve economical and nutrition problems. For example countries of Middle East are rich with oil and despite the Arabian peninsula desert climate they trade and can receive food products from other countries. Due to these circumstances, the qualitative and quantitative sufficiency of population nutrition is satisfied.

Countries with dry climate which don't have considerable natural resources can't effectively solve the problems of sufficient nutrition for their population (e.g. Ethiopia).

Local peculiarities of food production also influence quality and quantity of nutrition. In dry regions, savannah, half-deserts, cattle-raising is spread thus one side nutrition of cattle origin food is used. In other, humid regions, food of plant origin prevails. Ethnic and religious traditions also play an important role in nutrition of certain countries’ population.

From the "Hygiene of nutrition" section (topic  23) it is known that rational nutrition is nutrition which provides normal organism growth and development, its high working ability, resistance to negative environment factors influence.

Conditions of rational nutrition are the following:

-         energetic value of food intake. It means correspondence to organism energy expenditure, including undigested part of food (in middle climate this part is 10%, in tropical climate it is considerably more);

-         quality value of dietary intake, which means presence of all substances in necessary amount and their balance;

-         rational diet. It means correspondence of food intake to biological rhythms (food intakes in certain time of the day). Also the certain number of food intakes, intervals between them, balance between the values of different food intakes during the day;

-         enzymatic constellation. It means correspondence of food products quality to enzyme ability of individual digestive system (quality of culinary processing, condition of food intake, spices, and other factors, that make the food easy for digestion and assimilation).

- epidemiological and toxicological food safety which means the absence of infectious organisms, helminthes and poisoning substances in toxic concentrations;

According to WHO data energetic and quality nutrition value of some developing countries population doesn't correspond to physiological requirements and famine is spread in some cases.

The energy and protein deficiency can cause the edematous form of starvation – Kwashiorkor, which affects children first of all. This disease affects muscles and lower extremities swell so much that toes can't be seen under the swelling. Person losses physical strength, working ability, anemia can appear.

In conditions of the total starvation, predominant energy deficiency in tropical regions may cause the cachexia, which is characterized by growth delay, severe atrophy of muscles and subcutaneous fatty tissue. Skeleton contours are seen under the skin and the head is disproportionally big.

In tropical developing countries children suffer from sprue, alimentary dwarfism, after breast diarrhea, anemia, liver cirrhosis, debility.

Among vitamin deficiency diseases (hypo- and avitaminosis) there are malignant anemia, scorbutus, xerophthalmia, beri-beri, rachitis, keratomalacia, pellagra, ariboflavinosis etc..

Endemic diseases of minerals deficiency or excess amount of microelements are typical for some localities: endemic goiter, caries, teeth fluorosis, rachitis, iron deficiency and microcytic hypochromic anemia, selenodeficiency miopathy, molibdenosis, Keshan disease, alimentary selenosis etc.

On the other hand among well provided population such diseases as obesity, gout, atherosclerosis, hypertension, urine acid diathesis, hypervitaminosis and brain blood circulation disorder can appear.

Diseases are also connected with poverty and low culture level of population and poor food quality and they are manifested by high temperature when microorganisms reproduce and preserve their virulent properties.

The most widely spread are the following diseases bacteriological, amoebic dysentery, typhoid fever, patatyphoids, hepatitis A, poliomyelitis, zoonotic infections, food poisoning of microbial and non-microbial origin, enzymopathia, food allergies, bio- and geohelminthosis.

Suppressed appetite is one of peculiarities of hot climate, also there are disorders of food digestion which are caused by spices. (The supressed appetite and digestion are the hot climate particularities. That is why spicy meals with pepper and other digestive system stimulators are used.) People change their diet by taking food in the evening and in the morning instead of day time.

Hygienic characteristic of widespread food products of tropical region

Cereals are widespread among plant food products in arid and humid tropical areas. Wheat contains 10-20% of protein in cellulose, which causes bread pores; rice - 12% of proteins and cellulose - 1% and it’s used for cereals but not for bread,maize (corn) - 7% of proteins, millet, sorghum, gaoliang - 10-13% of proteins. Fungi (ergot, brand, aspergillus etc.) especially after heavy rainfalls, present in cereals may be harmful for human health and can cause micotoxicosis.

Beans are also widespread because they are rich with proteins (15-17%), fats (6%), tough cellulose and soy (18-19% fats) and peas, lentils, chick-pea etc.

Oil-bearing crops are widespread too. They are ground peas, coconut tree, rape, wild turnip/bittercress, mustard, olives, sesame, safflower, cocoa, tung-tree, cotton-plants. These plants are characterized by significant amount of polyunsaturated fatty acids  linoleic acid (33-50%), oleic acid (29-44%).

Manioc is prevalent among vegetables in tropical countries, especially in humid tropics, savannas. Weight of manioc tuber is 2 kg, it contains 24% of carbohydrates, 1% of proteins, 0.5% of fats, 3% of cellulose. Some sorts have up to 80 mg/kg poisonous cyanogenic glucosydes and may be harmful for health.

The sweet potato or yam is the second widely spread vegetable in tropics and subtropics. Its tuber weight is 4-5 kg. It contains 24% of carbohydrates, 2% of proteins, 1.5% of fats, 3% of cellulose. In the South-East Asia and Oceania, yams aregrown, which contain 29% of carbohydrates, 25% of proteins, 0.03% of fats, 1% of cellulose. There is a sago palm in Indonesia and Malaysia and starch groats as it’s made of core of its trunk. Sago contains 80% of starch, 3 % of proteins, 0.25% of fats. In hot climate regions pumpkins, melons and watermelons are widely used.

Among fruits citrus plants are widespread: oranges, tangerines, grapefruit, shaddocks, lemons, citrons, kumquats. These fruits are rich with sugar, organic acids and have significant dietetic properties.

Bananas play significant role in nutrition of tropics population because they are rich with sugar and vitamins, they contain 22-27% of carbohydrates, 1.3-1.5% of proteins, 0.1-0.6% of fats.

In arid areas of Asia, Africa, date palms are grown. They are called “desert bread” because of their nutritious properties. It contains 72% of carbohydrates, 7% of proteins, 2,5% of fats, 3-6% of cellulose, vitamins B.

In Indonesia and Polynesia bread tree and jackfruit are cultivated. They contain 19% of starch, 12% of sugar, 1.5% of proteins, 0.2-0.5 % of fats. Mango, mangosteen, tamarind, loquat are used in the South Asia; the pineapples, guava, sapota, avocado - in the Central America. All these fruits have high nutrition and taste qualities.

Full-value protein deficiency is significant disadvantage of these plants. Also they don’t contain enough essential acids, or the wrong balance between them, except soy and legumes. In case of one side nutrition with these plants and without sufficient assortment, the partial protein deficiency and anemia (due to the meat products’ hemoiron absence) develop.

  

Methods of medical control of sufficiency and safety of tropical regions’

population nutrition

 

In developed countries of tropical region medical control methods are similar to those, which are used in Europe. They are the following:

-         methods of nutritional status assessment of research population group;

-         methods of energy expenditure assessment, organism energy and necessary substances of dietary intake provision (calculations and laboratory methods of research);

-         methods of expert assessment of food products and ready meals for their freshness and safety (see chapter "Hygiene of nutrition").

In developing countries these methods are used by medical service in big cities or centers of administration. In rural regions these methods are applied but their results and implementation are not very effective.

Based on these results and according to the WHO recommendations, the Methods and measures of preservation and storage of food products in tropics are developed and introduced. They consider usage of antibiotics and preservatives etc.

Methods and measures of alimentary and foodborne infections and invasions, microbial and non-microbial origin food poisonings prevention are developed. Sanitary culture elements, sanitary education of population, prophylactic immunization (vaccination) etc. play significant preventive role.

 

Calculation methods of nutrition assessment and correction

 

4.1. Method of alimentary calorimetry by P.E. Kalmukov

This method allows to determine the total sum of energy expenditure for certain research period and to make corrections of intake in case of weight loss or excessive gain. It can be done by intake calories calculation in condition of adequate nutrition (taking into account part of ration which wasn't eaten) and with permanent body weight.

Researches are carried out for 15 days. If body mass doesn't change during this period - energy expenditure corresponds to digested food energy (10% of eaten intake isn't digested). If during this period a person looses weight, we can considerthat every 1 kg of body weight loss equals 4 100 kcal shortage for both for adults and children, and every 1 kg of weight gain equals extra 6 800 kcal for adults and 5 000 kcal - for children. These figures are called energy equivalents (EE).

During calculations it should be considered, that ideal theoretical body mass by Brock's index equals height in cm minus 100.

During nutrition correction for people with body weight loss, corresponding food amount is added to ration and for people with excessive weight, food amount is decreased but not less than by l 000 kcal (the level, at which the nitrogen balance (protein nutrition index (PNI, %) is not yet disturbed). Protein nutrition index is urea nitrogen share in general nitrogen content in urine in %.

Example 1. Adult person has excessive body mass of 10 kg, and in order to decrease it to ideal theoretical body mass he gets limited ration of l 000 kcal instead of necessary 3000 kcal per day. How long can this intake be used without pathological changes in the organism?

Calculation:    

Example 2. Person performs medium intensity physical work, and receives intake, worth 3 000 kcal, during 15 days. During this period, person looses 1 kg of body mass. How can the daily intake be optimized?

Calculation: Body weight decrease by 1 kg during 15 day means 4 100 kcal shortage. Thus, addition to the daily intake is:

Addition 

 

4.2. Methods of proteins and fats sufficiency assessment.

Protein sufficiency is calculated using protein nutrition index (PNI) which is expressed in % corresponding to urea nitrogen correlation to total nitrogen in urine (see table 1).

Table 1

Protein nutrition index, %

Level of protein nutrition

95-90

adequate

90-85

sub adequate

85-80

low

80-70

sub compensated

70-30

insufficient

30-25

significant disorder

 

Fat sufficiency is calculated using the following formula:

D= M × C × 0.0632

where:    D - fats amount in g;

M- middle subcutaneous thickness in mm (it is determined under lower angle of the right scapula, on the back surface of the right shoulder and on the side surface of belly);

C - body surface in cm2, determined according to the table 2.