The effects of high temperatures on the human body
Published Time:
2016-06-14
1. Human Thermoregulation
The state where the body's heat production and heat dissipation maintain a relative balance is called human thermoregulation. Maintaining a constant body temperature is crucial for normal metabolism and physiological functions. The relationship between heat production and dissipation determines whether the body can maintain thermal balance or if internal heat accumulation increases.
Under normal conditions, heat dissipation occurs through radiation, conduction, and convection. In high-temperature environments characterized by high temperatures, strong radiation, and high humidity, workers experience difficulty with radiative and convective heat dissipation; heat dissipation relies solely on evaporation. In high-temperature, high-humidity conditions, not only are radiative, conductive, and convective heat dissipation ineffective, but evaporative heat dissipation is also hindered.
2. Ambient Temperature and Body Temperature
In high-temperature work environments, body temperature often increases to varying degrees, and skin temperature can also rise rapidly. In high-temperature environments, the body enhances heat dissipation in the following two ways to maintain normal body temperature.
(1) In high-temperature environments, peripheral blood vessels reflexively dilate, increasing skin blood flow and skin temperature. This increases heat dissipation from the skin through radiation and convection.
(2) Sweat glands increase sweat secretion, increasing heat dissipation through sweat evaporation. The evaporation of 1 gram of sweat from the skin surface absorbs 600 kilocalories (2.51 megajoules) of latent heat. The amount of sweat produced is affected not only by ambient temperature but also by work intensity, ambient humidity, and wind speed.
3. Water and Electrolyte Metabolism
At room temperature, a normal person takes in and excretes approximately 2-2.5 liters of water daily. In hot seasons, a normal person sweats about 1 liter daily, while in high-temperature environments performing strenuous physical labor, sweat production increases significantly, averaging 3-8 liters daily. Since sweat is primarily water, containing a certain amount of inorganic salts and vitamins, profuse sweating significantly affects the body's water and electrolyte metabolism, and also has some impact on trace element and vitamin metabolism. When water loss reaches 5%-8% of body weight and is not replenished promptly, symptoms such as weakness, thirst, oliguria, tachycardia, fever, and water and electrolyte imbalance may occur, reducing work efficiency.
4. Digestive System
During high-temperature work, blood redistribution occurs, with peripheral vasodilation and vasoconstriction in the abdominal viscera. This can cause gastrointestinal anemia, potentially leading to reduced secretion of digestive juices (saliva, gastric juice, pancreatic juice, bile, intestinal juice), decreasing the secretion of free hydrochloric acid, proteases, lipases, amylases, and bile acids necessary for gastrointestinal digestion, and consequently impairing gastrointestinal function. Significant sweating and chloride loss reduce the chloride ion reserves needed for gastric acid formation in the blood, also leading to decreased gastric acidity. This can result in decreased appetite, indigestion, and other gastrointestinal problems. Because gastric emptying accelerates in high-temperature environments, food enters the duodenum before chemical digestion is complete, preventing adequate digestion.
5. Circulatory System
In high-temperature conditions, profuse sweating leads to blood concentration. High temperatures cause vasodilation, increasing peripheral blood circulation. The need for physical exertion also increases muscle blood flow. These factors can cause tachycardia and reduced stroke volume, increasing cardiac burden and altering blood pressure.
6. Nervous System
Under high temperature and thermal radiation, the excitability of the cerebral cortex regulatory center increases. Due to negative induction, the motor function of the central nervous system is inhibited, resulting in decreased muscle work capacity, accuracy, coordination, reaction speed, and attention, increasing the risk of workplace accidents.
7. Other
In addition, high temperatures can increase the burden on the kidneys, reduce the body's tolerance to the toxic effects of chemicals, making the toxic effects of poisons more pronounced. High temperatures can also reduce the body's immunity, suppress antibody formation, and decrease resistance to disease.
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