Electricity is a process where electrons are passed from atom to atom similar to how a bucket brigade passes pails of water. Typically, these electrons travel through electrical wires that deliver the electricity to its intended destination. For example, power lines transport electricity from power plants to homes and businesses. Insulated wires are then run throughout these buildings so that people can access that electricity at designated power outlets.
Electrical burns account for almost 4% of all burn injuries that require burn center treatment. They occur when electrical currents jumps from a wire, cord, outlet, or appliance and pass through a human body. Skin offers resistance to electricity entering the body, but once electricity has entered the body it is conducted fairly readily leading to potentially serious internal injuries. The type and extent of an electrical injury is determined by current strength, voltage, resistance, duration of contact with the electrical source, pathway of flow, and the circuit type.
Amperes (amps) is the unit of measurement used to describe the strength of an electrical current. Every time 6.242 x 1015 electrons pass a given point in one second, one ampere of current has passed. Milliamps (1/1000th of an amp) are commonly used to describe current strength in connection with the human body. Most people feel a tingling sensation between 1-4 milliamps.
The let-go current is the maximum current strength at which someone can grab and then let go of the source of an electrical current before it impossible for the person to release. The let-go current differs for children (3-4 milliamps), women (6-8 milliamps), and men (7-9 milliamps). After this point, muscle tetany sets in. Muscle tetany is an involuntary contraction of a muscle which can be caused by the flow of an electrical current through the muscle.
Most people are more familiar with referring to electricity in terms of voltage. Voltage describes the force that propels electrons in the same direction. Higher voltages propel larger amounts of electrons over a set increment of time. The table below provides approximate voltage values for context.
|AAA Battery||1.5 V|
|Automobile Electrical System||12 V|
|Household Electricity||120 V (Average in North America)|
|High Voltage Electrical Power Transmission Lines||110 kV (kV = kilovolts; 1,000 times greater than V)|
|Lightning||100 MV (MV = megavolts; 1,000,000 times greater than V)|
Electrical burns can often be divided into the categories of low-voltage and high-voltage burns using 500V as the cutoff point between the two. Low-voltage burns occur almost exclusively on the hands or mouth and follow the pathway of least resistance—nerves, blood vessels, etc.
High-voltage burns can occur on any part of the body and follows the most direct, not least resistant, pathway. As a result, the current is concentrated at both its entrance and exit from the body and commonly leaves blackened patches of skin at the entry and exit points. These types of burns are more likely to affect vital organs that exist between the entry and exit point and are especially fatal when the current passes from hand-to-hand.
A particular type of high-voltage burn is an arc burn. Arc burns do not require any direct contact with an electrical source. Instead, an arc burn is the product of an electrical arc that forms between objects of differing electric potential (normally a highly charged source and something with grounding capacity) which come into near proximity with each other. Electrical arcs can reach temperatures as high as 9,000 °F. An electrical arc can contact a victim leading to arc burns, or the simple proximity to the heat of an electrical arc can produce thermal burns.
Resistance describes the impedance of the flow of electrons. What determines the resistance of a substance is the strength of the bond between the nuclei and outer electrons. Low resistance substances (such as copper and silver) are called conductors and have weak bonds. High resistance substances (such as rubber or glass) are called insulators and have strong bonds.
The body has higher resistance on the outside and lower resistance internally. Skin resistance is affected by the moisture content, thickness, and cleanliness. Calloused skin may be as much as 200 times more resistant than typical skin whereas wet skin may be only 1/5th as resistant. The dermis—a thick layer of living tissue below the epidermis that contains blood capillaries, nerve endings, sweat glands, hair follicles, and other structures—is less resistant than the epidermis. Blood vessels, muscles, and nerves have high electrolyte and water content which gives them low resistance and makes them good conductors. Bone and fat have a higher resistance. This is one reason why electrical burns may lead to large amounts of 2nd or third 3rd degree burns without reaching the 4th degree.
There are two types of circuits that electrical currents can flow in. They are direct current (DC) or alternating current (AC).
Direct current is a current that flows in only one direction and is produced by sources such as batteries, solar cells and dynamo type electrical machines. DCs maintain a single voltage level, meaning it has a frequency of zero. As a result, shocks from a DC cause a single, large muscle contraction. Muscle contractions normally push the individual away from the electrical source resulting in only brief contact with the source.
Alternating current is a current in which the flow of electrons changes direction in rhythmic fashion and is the most prevalent type of electricity in homes and offices. The rhythmic change in electron direction in an AC coincides with changes in voltage level. The voltage level continuously moves between a maximum positive value and maximum negative value. Every time the voltage passes through zero, the current changes directions. AC is considered to be approximately three times more dangerous than DC of the same voltage. In part, this is because the rhythmic flow of electrons causes numerous muscle contractions instead of one large muscle contraction. The result is that muscle tetony that holds the victim in place or even leads to the victim grasping the electrical source. This in turn leads to longer contact duration and more electrical energy enters the body.
Work place hazards are by far the most common source of electrical burns. Work related accidents account for over 60% of electrical burns that require burn center treatment. Not surprisingly, these injuries occur predominantly among males ages 20-60. Professionals in fields such as cable repair, construction, and electrical repair are at the greatest risk.
Downed utility lines also present a significant safety hazard. The minimum OSHA recommended safe distance away from a downed utility line is 10 feet if the utility line is less than 50,000 volts. If the utility line is 500,000 volts the minimum OSHA recommended safe distance is 18 feet. If you’re unsure about the lines voltage, err on the side of caution.
In young children, oral electrical burns are most common. Oral electrical burns are a specific type of low-voltage burn that results from infants biting on or placing an electrical cord in their mouth. In oral electrical burns the current passes from one side of the mouth to the other and can seriously damage the oral cavity. The Electrical Safety Foundation International estimates that every day nearly 7 children are treated in hospital emergency rooms for electrical shock or burn injuries caused by tampering with a wall outlet.
The Burn Injury Management page has full information on treatment for each of the various burn types. A few basic guidelines when dealing with electrical burns include the following: never approach or touch the victim until the source of the burn has been turned off. Electricity will travel through the victim and into anyone providing care unless protective measures are taken. No one benefits by creating multiple victims in an effort to help the initial victim.
Electrical injuries are complex and often extend beyond the burns seen on the surface. Internal organs can be damaged. For all electrical burns, other than minor shocks with no marks to the skin, it is recommended that the victim receive professional medical attention. Medical professionals will be able to verify if involuntary muscle contractions caused any bone fractures or dislocations; if there was any interference with electrical conductivity of organs, such as the heart and nerves, which could lead to seizures or cardiac arrest; and if there is any damage to veins or arteries.
As with all burns, the best practice is to take safety precautions to avoid burns in the first place. The American Burn Association provides a variety of helpful tips to help avoid electrical burns.
- Disconnect appliances by pulling on the plug, not the cord,
- If an appliance has a three-prong plug, use it only in a three-slot outlet; never force it or remove a prong to make it fit a two-slot outlet,
- Check electrical tools regularly for signs of wear,
- Replace cords that are frayed or cracked,
- Replace any tool if it causes even small electrical shocks, overheats, shorts out or gives off smoke or sparks.
- Never use electrical appliances near water,
- Unplug any appliance before repairing it,
- Attach extension cords to appliances before outlets,
- Keep potentially combustible items at least three feet away from all heaters, AND
- Keep everyone out of the area and call 9-1-1 or your local electric utility if you see a downed line.
If you have children, take extra precautions.
- Don’t allow children to play with or near electrical appliances,
- Use plug covers on any electrical outlets accessible to small children,
- Outlet caps that attach to the outlet plate with screws give better protection than those that plug in,
- Make sure any night lights used in child’s room do not resemble toys,
- Make sure such caps are not big enough to be a choking hazard,
- Make sure plug in caps are a similar color to the outlet,
- Teach children to respect electricity as soon as they are old enough.