Tropical Hygiene

TROPICAL HYGIENE. The main feature of the climate of tropical and subtropical areas, of interest from the standpoint of practical hygiene, is the intensity of solar radiation. The tropical zone is also characterized by a regular wind regime accompanied by a regular annual course of cloudiness and rainfall. In world literature, practically tropical climate is considered the climate of humid coasts, since in tropical countries these very areas, favorable for the establishment of all kinds of plantations, are predominantly inhabited by man. In the USSR only the southern part of the Caucasian coast of the Black Sea from Tuapse to Batumi and the southern part of the coast of the Caspian Sea (Lenkoran) have a climate approaching that of subtropical places. The Central Asian republics only border the subtropical zone, but due to the continentality of the climate, very high temperatures are reached in the summer months, which poses a whole series of questions to practical hygiene, common with the questions of hygiene in the tropics proper. The direct influence of tropical climate on man is manifested primarily along the line of thermoregulation and the associated water exchange, as well as through the action of chemically active rays. If at a latitude of 53°, 49% of the rays of the violet part of the spectrum reach the earth's surface (the rest is absorbed by the atmosphere), then at a latitude of 30°, 61% of them reach, and at the equator - 65%. The greater richness of the solar spectrum with chemically active rays and the greater duration of the action of these rays determine significant pigmentation of the exposed parts of the body. The pigment, absorbing the thermal energy of solar rays, accelerates the onset of sweating and intensifies it. Sweating and water loss through the lungs are the main factors regulating body temperature in a hot climate. According to Rubner, in a temperate climate, heat loss due to the evaporation of water occurs only by 12%. With an increase in air temperature to 29°, already 70% of the heat given off by the body goes due to the evaporation of water. Calculations show that thermoregulation at high temperatures is determined almost exclusively by the ability of the surrounding air to absorb evaporating moisture. The latter circumstance explains the enormous importance of air movement for thermoregulation. Thus, at a temperature of 35° and 90% relative humidity, to dissipate the heat produced by the organism due to exchange at rest, 4 m³ of air must be used completely. Thus, high relative humidity, characteristic of the tropical climate of coasts, determines the particular discomfort of staying in this climate and requires special adaptations for continuous air circulation in the room. It should be noted that shade is not always a salvation with regard to overheating of the organism, since on the sun the humidity of the air decreases significantly, which promotes heat dissipation. A very unfavorable factor for the organism is also the absence of significant fluctuations in temperature during the day. It has been noted that prolonged stay in a uniform tropical climate weakens the function of regulatory mechanisms of heat production and heat dissipation and makes it difficult to return to countries with a temperate climate. An increase in water loss through the skin and lungs has great significance for metabolism: a large amount of various substances are excreted with sweat, on the other hand, the work of the kidneys is reduced. Pulmonary blood filling in the tropics turns out to be reduced, and the capacity of the lungs increases by 7-8%, breathing is less frequent and less deep, carbon dioxide excretion is reduced. The basal metabolism is reduced by 10-15% during prolonged stay in the tropics. The main purpose of clothing in the tropics is protection from solar radiation and from ripening. Clothing must also guarantee good ventilation and evaporation of water. Underwear must be soft so as not to cause irritation of the skin, irrigated with sweat, and elastic so as not to adhere to a wet body. A fabric made of a mixture of flax and paper is recommended. Clean paper, due to the thin hairs with which it is covered, has a tendency to mat, especially after repeated washing. Any dyeing of fabric reduces its hygroscopicity and permeability for air, as does sizing and starch. Underwear should therefore not be colored and should not be starched. Upper clothing should also be sewn from material that can be washed. The color of clothing determines its ability to reflect thermal rays and its permeability for chemically active rays. Light colors reflect the maximum amount of thermal rays. If the amount of thermal rays passed by white material is taken as 100%, then light yellow passes 102%, light gray 152%, red 158%, light brown 198%, black 208%. White material, however, is permeable to ultraviolet rays. Therefore, for outer clothing, material of a khaki color is recommended, not too thin. The thickness of the material is also significant from the point of view of its permeability for chemically active rays. In favor of thickness, however, the weight of the material should not be increased. The cut of clothing must guarantee good ventilation. Clothing should not tightly fit at the waist, at the collar, to avoid irritation of the skin and retention of moisture; it is necessary to avoid all lacing. Clothing should also be calculated for protection against insect bites - leg wraps, mosquito nets, etc. The headgear must guarantee air circulation - porous material, special holes. Helmets of the tropical type, having a circular ventilation space between the rim, adjacent to the head, and the outer cover, are useful. Shoes should also be easily ventilated (canvas). To combat excessive sweating of the feet, it is recommended to place shoes in hermetically sealed boxes at night, into which a vessel with a small amount of formalin is introduced. It is desirable to have two or three changes of shoes so that they can dry well. Hygiene of nutrition in the tropics must take into account the peculiarities of the need for food, the distribution of meals, and the influence of high temperature on the preservation of food products. Due to the decrease in metabolism during prolonged stay in the tropics and reduced heat dissipation, the total caloricity of the ration can be slightly reduced compared to a temperate climate. Meat nutrition, as increasing the organism's need for the introduction of fluid, should be limited by increasing the amount of plant food and fruits. Spices are recommended to stimulate the secretion of digestive juices. To compensate for the salts excreted with sweat, it is desirable to introduce a sufficient amount of salt; Due to the increase in metabolism caused by protein food, it is recommended to move lunch to cooler hours, towards evening. The need for the introduction of fluid in the tropics increases compared to a temperate climate by 2.3 times or more. Instead of pure water, drinks containing a certain amount of salts and tannin (liquid tea) are recommended, which quench thirst better, and with their introduction water is retained in the organism longer. Alcohol has a particularly harmful influence in the tropics. It disrupts thermoregulation, intensifies sweating, which is already burdensome, and increases the need for fluid, which leads to overloading the heart. "Maturation" of meat in the tropics is not always possible due to the possibility of fly attacks and rapid decomposition. At low night temperature, it is possible to kill the animal at night and leave the meat until morning protected from flies. Meat is best preserved in refrigerators at a temperature slightly above zero (from 0° to 4°). Frozen meat is not suitable for the tropics, since after thawing it undergoes bacterial spoilage extremely quickly. Fish spoils very quickly in the tropics. Canned goods are suitable only for single use of an open can, since the contents of open cans spoil quickly. Dried meat and smoked products can be used. The latter are preserved in hermetic packaging, in plaster or lime. Special precautions are needed to protect food products from contamination by flies, infected water, etc. For dishes, mesh cabinets and lids for dishes made of mesh, impermeable to flies, are necessary. Dishes in humid tropics tend to rust. Thorough tinning, enamel is recommended. Due to the easy decomposability of food residues, special attention must be paid to thorough washing of dishes. The need for water for all human needs in the tropics is higher than in a temperate climate, mainly in connection with the need for abundant ablutions. The water consumption per capita per day increases to 500-1000 l. Accordingly, water sources must be calculated. Reservoirs must be arranged so that they cannot serve as a source of reproduction of mosquitoes (meshing of cisterns). Water disinfection is carried out by chlorination or in filters of the cadin type. Water for drinking is best boiled. Scooping water, in which the water carrier's feet get into the water, is inadmissible (danger of introducing bacterial infections, typhus). The arrangement of housing in a hot climate must ensure its minimal heating, good ventilation, protection from insects and rodents. The long side of the house is desirable to be located from west to east, which leads to the least heating of the long walls.

When siting houses, the direction of the prevailing winds must be taken into account; the length of the building should be, if possible, perpendicular to the wind direction. In many cases, it is advisable to construct the house on piles to achieve ventilation from the floor level as well. Verandas are usually built on the north side. The architecture of Spanish houses, built in the form of a closed quadrangle surrounding a courtyard, is also advisable; the outer smooth walls have almost no windows or have ventilation openings covered by shutters; windows open into the inner courtyard. Living quarters should be equipped with fans, placed in pairs on opposite walls facing each other. To protect against tropical rains, wide roof slopes and shutters are necessary. Natural porous stone is recommended as the primary building material, followed by cement or concrete. In rainy areas, excessive shading of houses is undesirable; the sun must have access to the house so that the walls can dry. Kitchens and toilets are built outside the living house but are connected by a covered passage. In rooms, it is desirable to avoid pictures and extra carpets on the walls, behind which insects can hide. Shortly before the World War, special devices for cooling and reducing air humidity in rooms began to come into use. They are based on the principle of cooling air below its dew point followed by reheating to the desired temperature. For hospitals in the tropics, a barrack system is desirable. - The choice of site for a settlement must take into account the distance from the places of emergence of harmful insects. When planning settlements, it is necessary to avoid the crowding of houses, which hinders air circulation and intensifies heating due to the reflection of rays from the walls. To avoid intensified heating of the soil, it is recommended to arrange lawns between houses. The wild almond (Terminalia catappa), which grows quickly and has a flat crown that does not hinder the wind, is highly praised as a tree that provides shade. Soil toilets, burning of garbage, and timely removal of excrement are of special importance in the tropics due to the speed with which all residues decompose and the possibility of mass fly emergence. The removal of excrement in small settlements is done in barrels; in large cities, a well-organized sewerage system is necessary; garbage is burned. Great importance is attached to the observation of the condition of reservoirs and the taking of measures against the possibility of mosquitoes breeding in them. Puddles, barrels of water, accumulations of water in hollows, etc., are dangerous. Cemeteries are recommended to be located in places with low-lying groundwater. The construction of crematoriums is desirable. - On transport in the tropics, white-painted, well-ventilated wagons with windows protected from the sun and refrigerator wagons for products are recommended. Personal hygiene in the tropics requires the correct distribution of working and rest hours. It is necessary to get up early to use the cool morning hours for work and sports. Skin care requires a shower in the morning and a bath in the evening before dinner. Frequent splashing with water is not recommended to avoid skin irritation; in particular, excessive use of soap, which deprives the skin of its natural fat content, should be avoided. Excessive skin degreasing leads to the stagnation of sweat and the development of lichen tropicus. To prevent this very distressing condition, it is recommended to rub an indifferent powder into the skin after washing. For sleep, hard hair pillows and light porous mattresses are recommended. In some places in the tropics, long, very narrow rolls stuffed tightly with hair are placed along the body in bed; during sleep, these are grasped by the hand and foot, thereby reducing the contact of body parts and increasing the surface for heat dissipation. Of special importance is the provision of a correctly arranged mosquito net for the bed, impermeable to flies, mosquitoes, and gnats. The best material for a net is thick tulle. Eyes are protected from the action of bright sunlight by smoked glasses.

Sh. Moshkovsky. Lit.-see literature to article Tropical diseases.