eMedicine Specialties > Emergency Medicine > Environmental

Lightning Injuries

Author: Mary Ann Cooper, MD, Professor, Department of Emergency Medicine, University of Illinois at Chicago
Contributor Information and Disclosures

Updated: Jun 12, 2009

Introduction

Background

Over the last century, records for environmental injuries and mortality indicate that lightning has consistently been one of the top 3 environment-related causes of death and the second most common storm-related cause of death, exceeded only by floods. In typical years, deaths from lightning have exceeded deaths from tornados, hurricanes, and earthquakes. Extreme temperatures, including winter weather and summer heat, are generally the most common environmental killers.¹

Ninety percent of lightning strikes from cloud to cloud; only about 10% of lightning strikes are from cloud to ground (CG). Lightning starts with short (30-50 m) spurts of static energy in a cloud. The lightning retreats back to its origin, refills the original channel, and branches at the end of the original channel to make a second generation of 30- to 50-m channels. Lightning continues with the retreats and new generations until the charge is either expended (intracloud lightning) or randomly works its way downward to make a cloud-to-ground flash.²

Any object under or near the thundercloud will have an opposite charge induced in it, be it a television tower, a tree, a person, or a blade of grass. Multiple upward leaders of current rise from these objects. Most do not contact the main lightning channel but may have sufficient energy to cause injury. Eventually, the downward leader may join one or more of the upward streamers to complete the lightning channel. At that point, a return stroke fills all of the branches and the lightning becomes visible.

Pathophysiology

Lightning cannot be classified as either direct current or alternating current. Lightning is not "scalable"—one cannot use their experience and knowledge of 110-volt lines or high-voltage injuries to predict what lightning will do. The physics of lightning is incredibly complex and substantially different from the physics of generated electricity.

Probably the most important difference between lightning and high-voltage electrical injuries from an injury standpoint is the duration of exposure to the current, which also affects the path it takes. While the energy may flow through the person for an incredibly brief period, usually the vast majority of lightning energy flashes around the person's body surface. Lightning has only brief contact with skin, and, in most instances, the contact is too brief to burn the skin substantially. Entry and exit are inappropriate terms to apply to lightning injuries.²  

Lightning may injure an individual in 6 ways.^2,3,4

• Direct strike (approximately 3-5% of injuries)
• Side splash from another object (approximately 30% of injuries)
• Contact voltage from touching an object that is struck (approximately 1-2% of injuries)
• Ground current effect as the energy spreads out across the surface of the earth when lightning hits a distance away from the person (approximately 40-50% of injuries)
• Upward leader that does not connect with the downward leader to complete a lightning channel (approximately 20-25% of injuries)
• Blunt trauma if a person is thrown and barotrauma from being close enough to experience the explosive force of lightning

As can be appreciated from the estimated distribution of injury mechanisms, few individuals experience the full energy of a lightning strike. Most of the energy is mediated by other factors including the ground, the tree, or other object that once hit transmits it to the person. In fact, less than one third of affected persons have signs of burns. When burns do occur, they are usually superficial.

Internal burns are rare. Myoglobinuria is rarely encountered in lightning injuries, whereas cardiac and respiratory arrest, vascular spasm, neurologic damage, and autonomic instability play a greater role.⁵ Blunt force injuries from falling, being thrown by muscle contractions, or barotrauma from the explosive force of a nearby lightning strike may occur.²

Lightning strikes are primarily a neurologic injury that affects all 3 components of the nervous system: central, autonomic, and peripheral.

Frequency

United States

For the past 40 years, lightning has consistently been the second largest storm-related killer in the United States,⁶ with an annual mortality of 45-50 killed. Sources of lightning injury data (the National Center for Health Statistics and Storm Data) systematically underestimate the number of fatalities by 28-42% for 2 reasons.^2,7 Much of the data is taken from newspaper accounts, so if the clipping-service budget is cut or if people struck by lightning do not make the news, they are not entered into the statistics. In addition, most survivors do not need to be admitted and do not show up in medical data banks. 

Many survivors do not seek immediate medical care and only come to the attention of medical personnel when they seek care for effects of the shock that have not resolved by a few days after their injury. Because injuries are so infrequently reported compared with fatalities, a rule of thumb developed from many studies is that injuries occur about 10 times more often than fatalities do.

Although most injuries occur outdoors, a number of people are injured indoors every year, including individuals who incur landline telephone-mediated strikes.^8,9 Use of cell phones, iPods, and other portable electronic devices does not increase the risk of injury except by distracting the individual from paying attention to warning signs such as storm clouds and thunder.

Injuries range from tiny static electricity like exposures to cardiac arrest.^{2,10,11,12,13}  No good statistics are available for the distribution of severity across the injured population. 

International

Compiling and recording statistics internationally is also a challenge because of the lack of a good reporting system.

Lightning is much more common near the equator. Total annual fatalities are estimated to be about 24,000, and annual injuries are estimated to be about 240,000 for the tropical and subtropical areas of the world, where lightning is most common and the economies tend to be more subsistent, agrarian, and labor intensive than they are in the more developed and temperate climates.²  In general, lightning injuries and deaths decrease in any country as the economic system, urbanization, and housing improve not only because direct numbers exposed to lightning decreases but because housing that contains plumbing and wiring provides substantial protection.  

Mortality/Morbidity

The lightning fatality rate is 8-10%. Cardiac arrest at the time of the injury is usually the cause of death; however, injury from blunt trauma (eg, falling down a slope) can also be a mechanism of injury or death.

• Lightning injury is a neurologic injury, affecting all 3 parts of the nervous system.^{14,15,16,17,18,19,20,21,22}
  • Brain – Neurocognitive changes, sleep disturbance, personality change, seizures, learning disability, postconcussive headaches, nausea, attention deficit, distractibility
  • Autonomic nervous system - Regulation of blood pressure and cardiac response (positive tilt test results, dizziness, hypertension), GI insult, impotence, sympathetically mediated pain syndromes
  • Peripheral nervous system - Chronic pain, sensory problems
• Often, these injuries are ongoing and not easy to quantify or to treat.
• Survivors tend to be young, employed, family people who suffer loss of income and disability and become a large cost for the community as well as substantially changing the family dynamics and economic productivity.²³
• Although lightning injuries during recreational activities tend to predominate in developed countries, nearly one third of US lightning injuries are work-related, on-the-job injuries. In less developed, more labor-intense agrarian societies, the proportion of work-related injuries and deaths is probably higher.²⁴
• The most common days of injury in the United States are on Saturdays, Sundays, and Wednesdays, probably reflecting the recreational activities on the weekends. The most common time of day to be injured by lightning is from noon to 6 pm, with 6 pm to midnight following, related to not only when thunderstorms occur but also to when people are most likely to be outdoors.^2,1

Race

No direct relationship to race is known to exist. An indirect relationship may be present based on employment or recreational activities.

Sex

In a US study from 1959-1994, males were 4.6 times more likely to be killed and 5.3 times more likely to be injured by lightning than females. This is not because of any physiologic differences but is a consequence of males' increased exposure to potential lightning-strike situations, such as outdoor activities or work, as well as probably to their higher level of risk-taking behaviors.²

Age

The age groups with the highest incidence are people younger than 16 years and adults aged 26-35 years. Few adults older than 50 years are injured. This is probably related to the decreased chances of exposure of this age group during outdoor recreation or employment.²

Clinical

History

Lightning injuries are obvious if they occur in a group setting where witnesses are present. However, lightning injuries can be difficult to diagnose if the person presents without witnesses or is unable to relate the details of his or her injury.

Often, the person can relate what happened to them. However, it is common for the person to have anterograde amnesia or confusion.⁵ While the person may be able to carry on a reasonably coherent social conversation, giving demographic and billing data, the examiner may also observe that he or she repeats the same questions multiple times or may not remember events in the ED. More disturbing symptoms such as not recognizing a family member should be suspect.

Conscious patients most often complain of muscle aches, dysesthesias, and weakness, or other neurologic/musculoskeletal problems.^2,5

• Outside exposures
  • Lightning may strike as far as 10 miles in any direction from a thunderstorm, before the rain starts, or while the sky is still clear. At least 10% of lightning hits when blue sky is visible.^25,26,27,28
  • The most dangerous times for lightning injury are when the person underestimates the likelihood of being hit (ie, before the storm or at the apparent end of the storm).
• Risk factors
  • Only 3 factors determine whether something is statistically more likely to be hit by lightning: isolation, height, and narrowness of the tip of the object facing the cloud. Only the first 2 apply to people.
  • A common myth is that metal attracts lightning. Although metal easily conducts electrical energy once it is hit by lightning, metal does not attract lightning.
  • Cell phones, iPods, and other portable (not hard-wired) electronic devices do not increase the risk of injury except by distracting the individual from taking notice of nature's warning signs of dark clouds, thunder, and lightning. 
  • Clothing, footwear, wetness, or other physical factors do not affect whether someone is likely to be hit by lightning, although some factors may affect their likelihood of survival or injury pattern.^29,11
• Indoor exposures^25,26,27,18
  • In general, being inside a substantial, habitable building such as a house, library, or school is one of the safer areas to seek shelter. The increased safety is credited, in part, to the fact that these structures tend to have plumbing and wiring in them, acting as a Faraday cage to transmit any electricity around the inhabitants. Unfortunately, it is also true that lightning may hit or hit near a structure or recreational facility and be transmitted into the building through the plumbing, electrical wiring, emergency medical service (EMS) or fire dispatch radio, or other routes. This includes facilities with indoor pools, which should be evacuated using the same rules as outdoor pools. Individuals should avoid touching plumbing or objects that are electrically hard-wired to the structure's electrical system including computers and electronic games wired to televisions and computers.  
  • At the time of this writing, taking shelter in any structure that includes the word shelter (eg, bus shelter, sun shelter, park shelter, golf shelter, rain shelter) generally provides no protection. To date, national lightning-protection building codes (National Fire Protection Association: NFPA 780) address only physical protection of shelters but not for people using them. Many believe that these structures may substantially increase the risk of lightning injury by increasing the functional height of the individuals standing under them, by increasing the risk of a side flash or ground current from a transmitted stroke in structures with a lightning protection system, or by other mechanisms too long to go into in this discussion.
  • Being inside a fully enclosed metal vehicle is a very safe place due to the fact that electricity will flow along the outside of any metal structure that it hits, not due to the miniscule effect of rubber composite tires. While being inside a vehicle when it is hit has been likened to "being inside a garbage can where someone threw two cherry bombs" and may be quite unpleasant, there has never been a substantiated electrical injury to a person inside a vehicle unless they were touching a handheld radio hard-wired to those lightning rods on the outside of the car that we call antennas or some similar connection to the outside.
• Telephone injuries⁹
  • Hard-wired telephones become the conduit for the charge to enter or to escape from the structure (and the person). Although the telephone system may be grounded adequately for electrical surge protection, lightning is too fast and strong for typical grounding systems to be effective and reaches the person before the circuit breaker or other protection can be effective.
  • Injuries to persons using telephones or telephone headsets, such as those who take phone orders, used to be common but have decreased substantially now that wireless systems are more ubiquitous.  
  • Older portable phones, seldom used now in the United States, were a rare source of lightning injury to people standing within a yard or so of the base station or charger. Those injuries were caused by the lightning jumping from the charger to anything close by and have little to do with the phone the person was carrying.
  • No lightning danger is inherent to cellular phones. Although many reports of lightning injuries involve people who are using cellphones, these reports represent the ubiquity of cellphone usage and of their users' inattentiveness to weather conditions and have nothing to do with the phones themselves.
  • In the past, acoustic injury was possible from the loud static noise in the earpiece of early portable phones, but, to date, acoustic damage involving cellular phones has not been reported.⁹
• Blunt injuries
  • These injuries occur because of muscular contractions, which may throw the person many yards or cause the person to fall.
  • Barotrauma may also occur from the almost instantaneous expansion and contraction of the air near the column of a nearby lightning strike.

Physical

Physical presentation may vary from mild disorientation with no immediate physical signs to cardiac arrest (the only direct cause of death) and anoxic brain injury.

• Cardiorespiratory symptoms
  • Cardiorespiratory arrest is the only known direct cause of death but is still uncommon. Lightning acts as massive defibrillation, sending the heart into momentary asystole, from which the heart often spontaneously recovers. Autonomic nervous system control of cardiac rhythm has been shown to be affected by lightning. In addition, for unknown reasons, respiratory arrest usually lasts longer than the initial cardiac arrest; thus, a secondary cardiac arrest from hypoxia, from more serious brain injury prolonging the respiratory arrest, or from other unknown causes may occur.^2,5,11,12
  • Many changes may be observed on the ECG, but the most commonly reported is QT prolongation, which generally resolves over several months and does not commonly require treatment. The indicated treatment depends on the resulting abnormality.^2,11,12,13
• Neurologic symptoms
  • Patients who are awake are usually able to carry on reasonably appropriate social conversation. However, they may develop disabling neurocognitive deficits similar to those of people with blunt head injury, which may not be apparent until survivors attempt to return to their previous work and are unable to process new information, organize their activities, and multitask.^2,30
  • Acute pain, numbness, or other dysesthesias may be reported. Chronic pain syndromes may develop from lightning injuries and may be due to nerve injury, sympathetic nervous system injury, spinal column injury, or other causes.²
  • Sympathetic nervous system injury may cause vascular spasm; temporary paralysis and mottling of an extremity (keraunoparalysis); transient hypertension, which usually does not need treatment; and late problems with positive tilt test results, vertigo or dizziness, tinnitus, hypertension, and pain syndromes.^2,15,16
  • If the patient is unconscious, suspect and investigate anoxic brain injury or underlying brain injury.
• Dermatologic symptoms³¹
  • Deep burns: Because lightning usually has extremely brief contact with the skin, deep burns are rare.¹⁰ If burns occur, treat them like any other high-voltage injury, including investigating for myoglobinuria.
  • Superficial burns: Burns may appear linear (often secondary to vaporized sweat or rainwater), punctate, or in pathognomonic fernlike patterns.¹⁰ Burns may also be secondary to heating metal, such as necklaces, coins in the pocket, or cleats on the bottom of athletic shoes.
• Blunt injury
  • Consider concomitant myoglobinuria if blunt injury is present.
  • Fractures are uncommon and occur more rarely in lightning injuries than in high-voltage injuries. Being thrown tens of yards because of intense muscle contraction is frequently reported. If the patient has a history of a fall or being thrown a distance, investigate for fractures and blunt injuries.
  • Organ contusions, pulmonary hemorrhage, and cardiac contusions have been reported but are rare.
  • The ear is the sensory organ most commonly injured by lightning. Tympanic membrane rupture is common and may occur from concussive or explosive force, direct current entry (often associated with burns to the canal or disruption of the ossicles), or from basilar skull fracture. Hearing loss, tinnitus, and other eighth nerve symptoms including dizziness and unsteadiness are common.⁵
  • Nearly every type of eye injury has been reported with lightning injury, including cataracts, macular holes, retinal separation, and iritis.³² Cataracts may be a late sequela of lightning injury, as are chronic pain syndromes, sleep disturbance, and severe headaches.

Causes

• Despite popular belief, nothing attracts lightning. The primary physical factors that make an object statistically more likely to be struck are isolation, height, and narrowness of the tip of the object facing the cloud. Only the first 2 factors apply to people.
  • Risk factors include being outside without knowing the weather forecast, not paying attention to the weather, or not having or following an evacuation plan.
  • While lightning can be seen hundreds of miles away on the Great Plains or not at all in heavily forested areas, thunder usually can be heard for about 10 miles away. By the time one hears thunder one is already in danger and should be seeking shelter or seeking a safer shelter. "When thunder roars, go indoors!" is the theme taught to children for injury prevention and is the theme of National Lightning Safety Awareness Week.
  • The only reason that cell phones and iPods are dangerous in thunderstorms is that they distract the individual from paying attention to the weather and hearing thunder, the primary warning signal for lightning. They do NOT attract lightning.
  • Although lightning during recreation accounts for the most injuries, a large number of lightning injuries, as many as one third in some studies, are work related. In addition, a measurable number of injuries occur inside structures every year.
  • Certain geographic areas are more prone to lightning, such as mountain (between 1 pm and 6 pm), parts of Florida and the Gulf Coast, the Eastern Seaboard, and the major river valley areas of the Midwest. This primarily has to do with weather patterns, moisture content of the air, and updrafts.
• Hurricanes and, often, floods can be predicted days ahead of time, and tornadoes can be predicted minutes to hours in advance, allowing time for people to prepare, evacuate, or seek appropriate shelter. Small thunderstorm cells arise and disappear and lightning occurs far too often and unpredictably for the government to issue warnings for every event. The National Weather Service (NWS) issues severe storm or thunderstorm warnings upon danger of (1) straight-line winds faster than 60 miles per hour, (2) hail three-fourths inch or larger in diameter, or (3) tornadolike gusts.
  • Although more and more NWS offices in lightning-prone areas are warning of lightning risk, lightning safety remains primarily an individual responsibility that requires individual decisions for prevention.
  • Since 1997, the National Collegiate Athletic Association (NCAA) coach and sports medicine handbook has listed conditions under which practices and games should be called for lightning danger.²⁵ The book clearly states that individuals who believe that their life is in danger should not be punished for exercising judgment and evacuating the field, despite coaches' objections. Multiple professional and college level games, including those being televised, have been delayed or called for lightning risk in the last decade.  
  • One exception to the individual responsibility caveat is when an adult such as a parent or coach or an organization such as a pool, school, park, or scouting organization is responsible for children. In those cases, the adult or organization is accountable and responsible for being aware of lightning safety rules, exercising prudent judgment, having an evacuation plan in mind, and exercising that plan when appropriate to protect the children from harm and injury.
  • Event planners should be more proactive and may need to monitor the weather hours to days in advance. A number of online, real-time services may be accessed or subscriptions purchased. Some will warn via cell phones, pagers, or other electronic devices, which is particularly handy for camps and large outdoor sports venues. Lightning safety plans should include safer areas for shelter, appropriate signage and written material in event programs, and clear warning signals with different "all clear" signals.^25,27,18  
  • Lightning protection for stadiums and other outdoor venues, including the Olympics, can be done surprisingly inexpensively, particularly if initially planned in the construction.

• Search for CME/CE on This Topic »

• Lightning Injuries (Trauma)
• Burns, Lightning Injuries (Plastic Surgery)

• Environmental Exposures and Injuries Center
• Lightning Strike Overview
• Lightning Strike Causes
• Lightning Strike Symptoms
• Lightning Strike Treatment