Electricity is a form of energy generated by the flow of electrons across a potential gradient from high to low concentration through a conductive material. Electrical shock injuries in humans are caused by contact with an electrical current, either natural lightning or mechanically generated.
Electrical injuries may be caused by accidents or by intentional misuse of electricity. There are similar risks from both occurrences.
Electrical injuries are classified according to three factors: power source (lightning or human-generated electricity); voltage (high or low); and type of current (alternating or direct). Each is associated with certain patterns of injury. Most electrical injuries are accidental.
The minimum current that humans can feel is 1 milliampere (mA). An ampere, named for the French mathematician and physicist André-Marie Ampère (1775–1836), is a measure of the amount of electric charge passing a given point per unit of time. One ampere represents 6.241 x 1018 electrons passing a given point in a wire in one second of time. In general, a current of 100 mA will be lethal if it passes through sensitive parts of the human body; a current as low as 60 mA can cause ventricular fibrillation, irregular contraction of the muscles in the two lower chambers of the heart.
Electric shocks have been used in medicine to treat mental illness, particularly depression (electroconvulsive therapy or ECT); to correct irregular heart rhythms (defibrillation and cardioversion); and to relieve pain by stimulating opioid receptors in the central nervous system (transcutaneous electrical nerve stimulation or TENS).
Electricity was used as a form of torture or punishment almost as soon as it was known to cause accidental workplace injuries. Since the 1930s, tyrannical regimes have used cattle prods and similar devices to torture people. Tasers are used by some U.S. police departments; these electroshock devices cause strong involuntary contractions of the muscles controlling movement, thus temporarily incapacitating suspects who may be violent or intoxicated.
Electrocution as a method of capital punishment was introduced in the late 1880s on the recommendation of a committee in New York State seeking a more humane method of execution than hanging. American inventor and businessman Thomas Alva Edison (1847–1931) recommended the use of alternating current to electrocute criminals, maintaining that it would cause instantaneous death. The first use of the electric chair in New York in 1890, however, was a disaster, requiring eight minutes to cause death. American engineer and entrepreneur George Westinghouse (1846–1914) is reported to have said that it would have been more humane to use an axe. As of 2015, only six states still use the electric chair for execution; it is a secondary option in all of these states.
Risk factors for electrical injuries include:
Electrical injuries were rare in industrialized societies until the 1870s and 1880s, when a series of inventions by Thomas Edison and George Westinghouse made it possible to transmit electricity over long-distance wires from one location to another for commercial and scientific purposes. The first fatal industrial accident involving an electric shock occurred in Lyon, France, in 1879.
As of the early 2010s, electrical injuries were responsible for about 1,000 deaths in the United States each year, or about 1% of all accidental deaths. About one-fourth of these fatalities were caused by natural lightning. Electric shocks are responsible for approximately 5% of all admissions to specialized burn treatment units in North America.
In the United States, about 80% of all electrical injuries occur in adult men, largely because of occupational choices. Among children, the male: female ratio is 3:1. Low-voltage injuries are most common among toddlers; high-voltage injuries primarily affect risk-taking adolescents and adults in high-risk occupations.
According to the U.S. Bureau of Labor Statistics, electric shocks are the second leading cause of death in the construction industry in North America. With regard to injuries caused by contact with overhead power lines, between 27% and 60% of cases resulted in more than 31 days lost from work—compared to 18% to 20% for all other occupational injury and illness. Injuries caused by electric shocks are also costly to employers. In fact, a researcher at the Electric Power Research Institute in Palo Alto, California, estimated that the cost to American employers is approximately $15.75 million per case in direct and indirect costs.
Electrical injuries cause damage to the cells of human tissues, and the resulting symptoms can affect a wide range of systems within the body.
Electricity damages the cells in human tissues in two basic ways: heating and blast force. The passage of electrical current through cell membranes causes their temperatures to rise, leading to disruption of the cell membrane itself (at 108°F, or about 42°C); denaturation of protein molecules in the cell (at 113°F, or 45°C); and destruction of deoxyribonucleic acid (at 149°F or higher, or 65°C or higher), which is commonly denoted as DNA, or the material that carries an organism's genetic material. Inmost cases of high-voltage electrical shock, heat damage occurs immediately at contact points but requires one to three seconds to injure deeper tissues. The blast force of electric current can cause significant blunt trauma injuries.
The overall severity of electrical injury depends on the current's pressure (voltage), the amount of current (amperage), the type of current (direct [DC] versus alternating [AC]), the body's resistance to the current, the current's path through the body, and how long the body remains in contact with the current. The interplay of these factors can produce effects ranging from barely noticeable tingling to instant death; every part of the body is vulnerable. Although voltage primarily determines the severity of the injury, low voltage can be just as dangerous as high voltage under the right circumstances. People have been killed by shocks of just 50 volts. Electric voltage of 380 volts or less is considered low voltage. The U.S. national electric code defines high voltage as 600 volts or higher. High voltage is generated at power plants and is transformed down to approximately 120 volts for most wall outlets in homes.
Electric shocks can affect all the major organ systems in the human body. How electric shocks affect the skin is determined by the skin's resistance, which in turn is dependent upon the wetness, thickness, and cleanliness of the skin. Thin or wet skin is much less resistant than thick or dry skin. When skin resistance is low, the current may cause little or no skin damage but severely burn internal organs and tissues. Conversely, high skin resistance can produce severe skin burns but prevent the current from entering the body.
The nervous system (the brain, spinal cord, and nerves) is particularly vulnerable to injury. In fact, neurological problems are the most common kind of nonlethal harm suffered by electric shock victims. Some neurological damage is minor and clears up on its own or with medical treatment, but some is severe and permanent. Neurological problems may be apparent immediately after the accident or gradually develop over a period of up to three years.
Damage to the respiratory and cardiovascular systems is most acute at the moment of injury. Electric shocks can paralyze the respiratory system or disrupt heart action, causing instant death. Also at risk are the smaller veins and arteries, which dissipate heat less easily than the larger blood vessels and can develop blood clots. Damage to the smaller vessels is probably one reason why amputation is often required following high-voltage injuries.
Many other sorts of injuries are possible after an electric shock, including cataracts, kidney failure, and substantial destruction of muscle tissue. Victims may suffer a fall or be hit by debris from exploding equipment. An electric arc flash may set clothing or nearby flammable substances on fire. Arc flashes can produce light intense enough to cause permanent blindness as well as heat intense enough (5,000°F to 7,000°F, or 2,760°C to 3,870°C) to melt bone and vaporize the surfaces of nearby human beings and other objects. Strong shocks are often accompanied by violent muscle spasms that can break and dislocate bones. These spasms can also freeze victims in place and prevent their breaking away from the source of the current. Alternating current is considered three times as dangerous as direct current for this reason: high-voltage direct circuit (DC) tends to cause one strong muscle spasm that throws the victim away from the source, whereas the cyclical flow of electrons in alternating circuit (AC) of the same voltage causes paralysis of the muscles that holds victims in contact with the current.
Diagnosis relies on gathering information about the circumstances of the accident, a thorough physical examination, and monitoring of cardiovascular and kidney activity. When possible, witnesses of the accident should be questioned about the circumstances of the event, particularly if the victim has lost consciousness or normal mental status. The victim's neurological condition can fluctuate rapidly and requires close observation. A computed tomography (CT) scan or magnetic resonance imaging (MRI) scan may be necessary to check for brain injury. Blood and urine samples may be taken. In some cases, the doctor may make a trial incision into burned muscle to assess the extent of tissue damage. The tissue sample is frozen and examined under a microscope to see whether the muscle tissue is still viable. If an arm or leg damaged by electricity is determined not to be viable, immediate amputation is necessary.
Treatment of an electrical injury usually begins at the scene, although first responders will generally take the victim to an emergency department or specialized burn or trauma center as soon as possible. The victim of a severe electrical injury may be examined and treated by a variety of specialists, including emergency physicians, plastic surgeons, neurologists, ophthalmologists, and orthopedic surgeons.
When an electric shock accident happens at home or in the workplace, the main power should immediately be shut off and the emergency number 911 should be called. If that cannot be done, and current is still flowing through the victim, the alternative is to stand on a dry, nonconducting surface such as a folded newspaper, flattened cardboard carton, or plastic or rubber mat and use a nonconducting object such as a wooden broomstick (never a damp or metallic object) to push the victim away from the source of the current. The victim and the source of the current must not be touched while the current is still flowing, for this contact can electrocute the rescuer. Emergency medical help should be summoned as quickly as possible. Trained electricians must use line personnel's gloves to separate the victim from the circuit by a specially insulated pole. Looping a polydacron rope around the injured patient is another method of pulling the person from the electric power source. Ideally, the electrician or first responder should stand on a dry surface during the rescue. People who are trained to perform cardiopulmonary resuscitation (CPR) should, if appropriate, begin first aid while waiting for emergency medical help to arrive.
Burn victims usually require treatment at a specialized burn center. Fluid replacement therapy is necessary to restore lost fluids and electrolytes. Severely injured tissue is repaired surgically, which can involve skin grafting or amputation. Antibiotics and antibacterial creams are used to prevent infection. Victims may also require treatment for kidney failure. Following surgery, physical therapy to facilitate recovery, and psychological counseling to cope with disfigurement, may be necessary.
Safety laws enacted by the U.S. Occupational Safety and Health Administration (OSHA) and the 50 U.S. states have helped to provide safe working areas for those dealing with electricity, such as electricians.
The mortality rate for electrical injuries in the United States is less than 5%. Many survivors, however, require amputation or are permanently disfigured by their burns. Anxiety disorders are common in survivors of high-voltage electrical injuries. About 73% of pregnant women injured by lightning or high-voltage electricity lose the fetus. Injuries from household appliances and other low-voltage sources are less likely to produce extreme damage.
Prevention of electrical injuries in the home or workplace begins with age-appropriate education about the nature of electricity and the importance of safety measures. The National Safety Council in the United States and Hydro-Québec (a power company) in Canada have handouts, videos, quizzes, and fact sheets about electrical safety on their websites ( http://www.nsc.org/ and http://www.hydroquebec.com/security/index.html ), some of which are listed under Resources below. These materials are written for the general public and are intended to help people recognize dangerous situations and take steps to protect themselves and their families before an electrical accident occurs.
People who are employed in workplaces with high-voltage electrical equipment or whose jobs require working with electricity should follow all safety precautions recommended by the National Safety Council:
Parents and other adults need to be alert to possible electric dangers in the home. Damaged electric appliances, wiring, cords, and plugs should be repaired or replaced. Only people with the proper training should attempt electrical repairs. Hair dryers, radios, and other electric appliances should never be used in the bathroom or any other location in which they might accidentally be exposed to water. Young children need to be kept away from electric appliances and should be taught about the dangers of electricity as soon as they are old enough. Electric outlets require safety covers in homes with young children.
People should be particularly careful when using metal ladders outside or when installing outdoor television or citizen band (CB) radio base antennas, as accidental contact with an overhead power line can be fatal.
During thunderstorms, people should go indoors immediately, even if no rain is falling, and boaters should return to shore as rapidly as possible. People who cannot reach indoor shelter should move away from metallic objects such as golf clubs and fishing rods and lie down in low-ground areas. Standing or lying under or next to tall or metallic structures is unsafe. An automobile is appropriate cover, as long as the radio is off. Telephones, computers, hair dryers, and other appliances that can act as conduits for lightning should not be used during thunderstorms.
See also Occupational Safety and Health Administration .
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American Burn Association, 311 S Wacker Dr., Ste. 4150, Chicago, IL, 60606, (312) 642-9260, Fax: (312) 6429130, email@example.com, http://www.ameriburn.org .
American College of Emergency Physicians, 1125 Executive Cir., Irving, TX, 75038-2522, (800) 798-1822, Fax: (972) 580-2816, firstname.lastname@example.org, http://www.acep.org .
American Society of Plastic Surgeons, 444 E Algonquin Rd., Arlington Heights, IL, 60005, (847) 228-9900, http://www.plasticsurgery.org .
Chicago Electrical Trauma Research Institute, 4047 W 40th St., Chicago, IL, 80532, (773) 904-0347, (800) 516-8709, email@example.com, http://www.cetri.org/ .
Environmental Protection Agency, 1200 Pennsylvania Ave. NW, Ariel Rios Bldg., Washington, DC, 20460, (202) 272-0167, http://www.epa.gov/ .
National Safety Council, 1121 Spring Lake Dr., Itasca, IL, 60143-3201, (630) 285-1121, (800) 621-7615, firstname.lastname@example.org, .
Rebecca J. Frey, PhD
Revised by William A. Atkins, BB, BS, MBA