Electrical hazards take a variety of forms and produce different types of injuries.
The National Safety Council reported in its 2014 edition of Injury Facts that there were 961 fatal electrical injuries from 2008 through 2010 due to exposure to electric current, radiation, temperature, and pressure. While relatively uncommon, electrical injuries are noted for having the potential to be particularly debilitating, with a high morbidity and mortality. (Koumbourlis, 2002) The seriousness of electrical injuries stems in part from their ability to produce multisystem trauma and their association with a range of complications, including cardiopulmonary arrest, cardiac arrhythmia, hypoxia, renal failure, and sepsis. (Cooper and Price, 2002) Exposure to electricity may also produce long-term neurological and psychosocial effects and significantly influence the quality of life. (Pliskin et al., 1994; Noble et al., 2006) The principal injury events associated with electrical hazards are electric shocks and arc flash and arc blast. Low-voltage shock injuries result from direct contact of the victim with electric current, while high-voltage shocks typically create an arc, which carries electric current from the source to the victim without any direct physical contact. (Koumbourlis, 2002; Lee et al., 2000) Electric arcing, commonly referred to as arc flash, occurs when current passes through air between two or more conducting surfaces or from conductors to ground, and it has a variety of possible causes, including gaps in insulation, corrosion, condensation, and dust or other impurities on a conducting surface. (Workplace Safety Awareness Council)
Electric arcing may produce temperatures as high as 35,000 degrees and may cause severe burns, hearing loss, eye injuries, skin damage from blasts of molten metal, lung damage, and blast injuries. (Lee, 1982) A critical factor that influences the severity of direct contact with electrical injury is the type of current to which an individual has been exposed. Cooper indicates that exposure to alternating current (AC), the form of current typically found in homes and workplaces, is considered to be three times more dangerous than exposure to direct current (DC) of the same voltage because it is more likely to result in muscle tetany (involuntary contraction of the muscles), extending the duration of exposure. (Cooper, 1995) The exit wounds produced by direct contact with DC current are also more discrete than those produced by AC current. (Bernius and Lubin, 2009) Additional factors that determine the severity of injuries resulting from direct contact with electricity include the strength of the current, the resistance of tissues, the pathway of current, and the duration of exposure. The strength of an electric current, expressed in amperes, is a measure of the energy that flows through a conductor and is a critical determinant in the amount of heat that is discharged to an object. (Cooper and Price, 2002) However, energy and heat may be dissipated by resistance to electric current, and because different tissues or parts of the body offer different resistance to the flow of electricity, the same amount of voltage will produce different currents, and thus varying degrees of damage, in different tissues. (Cooper and Price, 2002; Koumbourlis, 2002; Bernius and Lubin, 2009) Bone, tendons, and fat offer the most resistance to current and will tend to heat up and coagulate, while nerves, blood, and membranes, and muscles offer the least resistance. Skin is the primary resistor to electric current and is an intermediate conductor, but its resistance varies with individuals and conditions. Wet skin, including skin wetted by perspiration, offers minimal resistance and will maximize the current to which it is exposed. The resistance of skin also increases with its thickness, making thick and calloused skin a poor conductor of electrical current. (Koumbourlis, 2002) Cooper and Price point out that resistance to electrical current increases with carbonization of tissue. (Cooper and Price, 2002)
The pathway taken by electric current through the body will determine which and how many organs are at risk and how much electrical energy is converted into heat. (Cooper and Price, 2002; Koumbourlis, 2002) Injuries to the heart and central nervous system are a particular concern. (Koumbourlis, 2002; Bikson, 2004) Current passing through the heart or thorax can cause direct myocardial injury or arrhythmias, while current through the brain may cause respiratory arrest, seizures, and paralysis. (Cooper and Price, 2002; Bernius and Lubin, 2009) Current following a vertical pathway on a parallel axis through the body is particularly serious because it is likely to involve the central nervous system, heart, and respiratory system. (Kombourlis , 2002) A horizontal pathway entering from one hand and exiting through the other may also pass through the heart, but not pass through the brain. (Kombourlis, 2002) In research conducted by Bailey and co-authors, a majority of electrocution when current followed a pathway from upper to lower extremities. (Bailey et al., 2001) Current that passes through the lower part of the body may cause serious injury, but is less likely to prove fatal. (Bikson, 2004; Bernius and Lubin, 2009)
Finally, more prolonged contact with electrical current creates greater opportunities for electrothermal heating, and thereby greater tissue destruction. (Cooper and Price, 2002) In addition to the potential for electric shock to cause serious burn injuries or injuries to vital organs, it can also cause severe muscle contractions and hemorrhaging of muscle fibers that result in fractures or dislocation of joints. (Leibovici et al., 1995) Shocks produced by voltages greater than 200 volts can cause damage to the eyes. (Leibovici et al., 1995) Electric shock can also result in secondary injury events, such as falls from height. (Bernius and Lubin, 2009). Exposure to high electrical voltages, typically classified as greater than 1000 volts, is associated with more serious injury because the greater current flow is likely to produce greater tissue destruction. (Cooper and Price, 2002) A review of electrical injury admissions at a hospital burn unit over a 20-year period found that complications were highest in the high-voltage group, and that this group had the longest mean length of stay and required the most operations. (Arnoldo et al., 2004) Lightning strike victims had the highest mortality rate (17.6%), but the mortality rate for high-voltage admissions (5.3%) was nearly twice that of low-voltage admissions (2.8%). Chudasama and co-authors (2010) also compared high and low-voltage injury groups at a burn center in order to compare outcomes on return to work and neuropsychiatric indicators. High-voltage injury victims had significantly larger total body surface burn areas, longer stays in the intensive care unit, longer hospitalizations, and significantly higher rates of fasciotomy (a surgical procedure which involves cutting the fascia to relieve tension or pressure to a limb), amputation, nerve decompression, and outpatient reconstruction. However, patients in low-voltage and high-voltage groups were found to have similar rates of neuropsychiatric complications, return to work limitations, and delays in returning to work.
A recent study of patients with electrical burns at a burn unit in Brazil also found that complications were more severe and common among patients in the high-voltage group, with longer hospitalizations and more complex surgical procedures due to the greater depth of burns. (Luz et al., 2009) As indicated in the studies comparing high-voltage and low-voltage electrical injury groups, exposure to low voltage electricity should not be taken to indicate low impact, particularly where low voltage is defined as up to 1000 volts. A study of low-voltage and electric flash injury victims by Theman and co-authors found that 57.5% of the patients attempted to return to work on average 107.7 days after injury, but only one – third of patients successfully returned to work 59.38 days after injury, and they concluded that return to work was complicated by continuing psychological, neurological, and musculoskeletal symptoms. (Theman, et al., 2008) A study of victims of electrical injury at a major Ontario burn center found that low-voltage electrical injury was associated with more frequent long-term complications than high-voltage injuries. (Singerman et al., 2008) Most of the low-voltage injuries were electrical flash burns (55% of study population). The most common sequelae (secondary consequences) among the electrical injury victims were neurological and psychological symptoms. Neurological symptoms most frequently involved numbness, weakness, memory problems, paresthesia, and chronic pain, while psychological symptoms most often involved anxiety, nightmares, insomnia, and event flashbacks. Patients who had more neurological symptoms also had more psychological symptoms. Many symptoms were non-specific and frequently were not manifested until months following the injury. A review of potential risk factors among electrocution victims in Quebec found that 25 of 124 victims were exposed to currents in the 240/120 volt range, and that wet extremities and passage of electric current through the thorax were more common in this group than in higher voltage electrocutions. (Bailey et al., 2001) Atrial fibrillation at low-voltage exposures is rare, but has been reported at less than 350 volts. (Varol et al., 2004) Exposure to less than 300 volts from household appliances may result in ventricular fibrillation. (Sances et al., 1979) Fractures may be produced by exposure to electricity in the 110 to 440 volt range. (DiMaio and Dimaio , 2001)