Physical and chemical agents can adversely affect the body; the severity of the effects depends on many factors. If exposure to the irritant is short in duration and frequency, is fairly localized, and the person is healthy, the damage may be unnoticed or reversible. However, if the person is debilitated, diseased, very young or elderly, has lowered resistance, or is on certain medications, the irritant may cause irreversible systemic damage.

Some of the more common physical and chemical agents include extreme heat and cold; ionizing radiation; extremes of atmospheric pressure; electric shock; poisoning; near-drowning; bites of insects, spiders, and snakes; asphyxiation; and burns.

Extreme Heat and Cold

Extreme heat (ICD-9: 992.x) may result in syncope (a transient loss of consciousness [ICD-9: 992.1]), heat exhaustion (ICD-9: 992.x), or heatstroke (ICD-9: 992.0). Causes of these disorders include overexertion in heat, prolonged heat exposure, salt depletion, dehydration, failure of the body’s heat-regulating mech anisms, or a combination of these causes.

Heat exhaustion, sometimes resulting in syncope, is caused by overexposure to heat and insufficient water and salt intake (ICD-9: 992.4). The person is usually pale and the skin is clammy. There is a rapid, weak pulse and shallow breathing. Individuals treated at this stage generally respond promptly to rest, cooling, and weak salty liquids administered orally. Heat cramps in the legs and abdomen result from heavy salt loss.

If the person does not respond or heat exhaustion is not treated, heatstroke may result when the body’s temperature-control mechanism malfunctions.

Heatstroke is a medical emergency. Sweating ceases and the body temperature rises. The skin becomes hot, dry, and flushed. Heatstroke may require hospitalization with intravenous (IV) therapy, cooling therapy, increased fluid intake, temperature monitoring, and muscle massaging. Hypersensitivity to heat may remain for some time. Any of the heat disorders mentioned can be fatal.

Extreme cold may occasion such disorders as chilblain (ICD-9: 991.5), frostbite (ICD-9: 991.x), and hypothermia (ICD-9: 991.6). Causes include overexposure to cold air, wind, or water. Chilblain, a mild frostbite, produces red, itching skin lesions, usually on the extremities, whereas frostbite, the freezing of exposed areas, causes tingling and redness followed by paleness and numbness of the affected areas. Untreated, either condition can lead to gangrene and may necessitate amputation. Hypothermia is a systemic reaction in which more heat escapes from the body than the body can produce; it can be fatal. Treatment of any of the cold disorders includes gradually warming the person, monitoring body temperature, protecting the affected part, preventing infection, and administering pain relievers, or analgesics, as necessary.

Ionizing Radiation

Depending on the duration and intensity of exposure and the form of the irradiating agent, the effects of ionizing radiation (ICD-9: 990) range from mild skin burns (ICD-9: 692.82) to fatal tissue destruction. The exposure to radiation may be via ingestion, inhalation, or direct contact. Causes include (1) occupational or accidental exposure and (2) the misuse of radiation for diagnostic or treatment purposes. Persons at risk include those with cancer who are receiving radiation therapy and employees in nuclear power plants. The harmful effects of radiation may be immediate or delayed, acute or chronic. Treatment is symptomatic and supportive and may include antiemetics, or drugs used to prevent or stop vomiting; simple and palatable foods; blood transfusions; and emotional support.

Extremes of Atmospheric Pressure

Extremes of atmospheric pressure result from a rapid change from a high-pressure to a low-pressure environment or from a low-pressure to a high-pressure environment. Decompression sickness (ICD-9: 993.3) is an occupational hazard for deep-sea divers and airplane pilots who descend or ascend too quickly and for hospital personnel who work in hyperbaric chambers. Systemic damage occurs following rapid decompression when gases dissolved in the blood and other tissues escape faster than they can be diffused through respiration. Nitrogen gas bubbles form in the blood and tissue, causing respiratory problems and pain. Treatment consists of emergency oxygen until the person can be transported to a hyperbaric chamber, where recompression is followed by slow decompression. Supportive measures are also important.

Electric Shock

Electric shock (ICD-9: 994.8) can occur anywhere there is electricity—home, work, or school. The causes of electric shock can be natural (as from lightning [ICD-9: 994.0]) or contrived (due to carelessness or ignorance, or from faulty equipment). The victim must be freed from the source of electric current without the rescuer contacting the current, and treatment must begin immediately. There may be very little external evidence of injury or severe and obvious burns. Other injuries may occur if the victim has been thrown clear of the electrical source by forceful muscular contraction. In this case, possible spinal injuries should be considered. Cardiopulmonary resuscitation (CPR) may be necessary. If the damage is severe, hospitalization may be required to observe the individual, treat any burns, and prevent infection.


Poisoning (ICD-9: 980.x-989.x) is a common occurrence, especially among curious children. In addition, society has become increasingly aware of poisonous chemicals that have been dumped or buried. Such chemicals cause soil and water contamination that result in ecologic and personal damage.

Poisons may be accidentally ingested, inhaled, injected, or absorbed through the skin, but poisoning can also be the result of occupational exposure when working with toxic chemicals; of improper cooking, storage, and canning of food; and of drug overdoses or abuse. Treatment consists of first aid measures, identifying and providing the correct antidote if one exists, and instituting supportive measures. The local poison control center offers valuable help. Prompt, correct treatment can save a life.


Near-drowning (ICD-9: 994.1) is more common during the warm summer months and could be prevented in many cases by following water safety precautions. In near-drowning, the person generally aspirates fluid, or the person may have an obstructed airway caused by a spasm of the larynx when gasping under water, resulting in hypoxemia (ICD-9: 799.02), or insufficient oxygenation of the arterial blood. Later, within minutes or possibly days of near-drowning, the person may experience respiratory distress. Emergency treatment is critical. Hospitalization may be required for oxygenation, airway maintenance, observation of the cardiovascular status of the client, and prevention of further complications.

Bites of Insects, Spiders, and Snakes

Insect, spider, and snake bites (ICD-9: 989.x) occur most often during the warm summer months. Bee, yellow jacket, wasp, and hornet stings may cause localized pain, but they usually require little more than symptomatic treatment. Allergic reactions and multiple stings or bites, however, are a more serious matter and are treated as a medical emergency. Poisonous spider and venomous snake bites require quick emergency measures to prevent venom absorption and life-threatening symptoms from occurring. The victim should be immobilized and transported immediately to a hospital, where the specific antidote can be administered. Whether the bite is considered serious or mild, close observation of the victim is essential.


Asphyxiation (ICD-9: 799.01), which is the lack of oxygen coupled with accumulating carbon dioxide in the blood, may result from near-drowning, hypoventilation, airway obstruction, or inhalation of toxic substances. Emergency treatment is generally required, and it may involve removal of any obstruction, CPR, oxygenation, and intubation. Hospitalization may be necessary to stabilize the victim’s vital signs. Obviously, any breathing difficulty is frightening to the victim, so reassurance and encouragement are needed.


Burns (ICD-9: 940.xx-949.xx) are classified by extent, depth, person’s age, and associated illness and injury. The rule of nines, a formula for estimating the percentage of a body surface burned by using multiples of nine, is useful for assessing the extent of burns. Figure illustrates the rule of nines and burn classification criteria. Burns are classified according to depth and how severe they penetrate the skin’s surface.

  • First-degree or superficial burns affect only the epidermis or outer layer of skin. A mild sunburn is an example. The skin is red, painful, and dry, but there are no blisters.
  • Second-degree or partial-thickness burns involve the epidermis and part of the dermis. The skin appears red, blistered, and may be swollen.
  • Third-degree or full-thickness burns destroy the epidermis and dermis skin layers. These burns may also damage underlying bones, muscles, and tendons. The skin appears white or charred; sensation is lost because nerve endings are destroyed.

Second- and third-degree burns require immediate medical attention. Emergency measures may be necessary to maintain the burn victim’s airway, cool the wound, and prevent serious loss of body fluids. Once the victim has been transported to a hospital, frequently a special burn center, the focus is on maintaining fluid balance and preventing infection. Severe burns can be extremely painful and require a lengthy rehabilitation period, including possible skin grafting and plastic surgery. Emotional support is essential.

Rule of nines and burn classification

FIGURE. Rule of nines and burn classification. (From Thomas, CL [ed]: Taber’s Cyclopedic Medical Dictionary, ed. 21. FA Davis, Philadelphia, 2009, p 2057, with permission.)