Lightning: effects on humans, risks at home?

In the event of a storm, lightning is a real danger. Each year in France, it affects between 200 and 300 people, causing nearly 30 deaths. What to do to avoid lightning? In a house ? What are the effects on humans in the event of a lightning strike and what to do when it happens?

On average, since 2000, 453,000 lightning strikes on the ground are detected in mainland France each year and 260 stormy days per year, indicates Météo France. Friday 3, Saturday 4 and Sunday 5 June 2022the context is favorable for the development of thunderstorms over a large part of the territory. It’s possible that these storms are sometimes virulent with hail, very strong gusts of wind and brief but intense rain. Monday, June 6, the weather will be mixed, but the risk of severe thunderstorms will have moved away“, details the site of Météo France. In the event of thunderstorms, lightning is a real danger. Every year in France, it affects between 200 and 300 people, causing nearly 30 deaths. How to protect yourself from it? What effects on the body? Advice from Michel Koutmatzoff, President of the Lightning Protection Association.

Definition: what is lightning?

Lightning corresponds to an electrical discharge that usually occurs during a thunderstorm. This electrical discharge can form inside a thundercloud – called cumulonimbus – between two clouds or between a cloud and the ground, thus causing a flash and a detonation. Because of the friction between the drops of water, the crystals and the grains of ice stirred up by the clouds, electrons (negative electric charge) are formed and are found attached to the heaviest elements accumulated on the base of the cloud. At the same time, the ice crystals, which are lighter, are found attached to the top of the cloud and constitute a positive electrical charge. It’s from this electrical potential difference that lightning is born. And depending on how far away you are from the thunderbolt, you can either hear a brief, powerful snap or a dull rumble.

A person standing in an open area (stadium, field, meadow) is a prime target for lightning.

Who is at risk of being struck by lightning?

The electric charges of the storm cloud seek to reach the ground as quickly as possible. Lightning therefore tends to primarily target the elements closest to the clouds. Logic : the higher an element, the thinner the layer of air to pass through for the electric discharge. This is why trees and tall buildings are the first elements affected by lightning. A standing person, especially in an open area, is also a prime target for lightning. Also, a mountaineer who often finds himself on summits or ridges is particularly exposed to lightning strikes.

What are the effects of lightning on humans?

The effects of lightning on human beings depend on the way in which it reaches them, the intensity of the electric current and the duration of its passage through the body.

Direct lightning strike

A person can be directly affected by the electric shock. Concretely “electric current enters the body through a point of impact (the entry point which is usually on the upper body) and exits through the exit point (which is usually found on the lower body) to reach the ground as quickly as possible“, explains Michel Koutmatzoff. A single landfill can contain up to 100 million volts and 200,000 amps, which is particularly dangerous for the organism. “This is the most violent lightning mode. This electric shock, in the same way that we put our fingers in a socket, can cause cardiac arrest, internal burnsand, in 10% of cases, the death of the person as a result“, underlines the President of the Lightning Protection Association.

Touch voltage lightning strike

© Luciano Cosmo – 123RF

A person can be struck by lightning after touching a metal object (post, fence, etc.). Concretely : the human body is in contact with a struck metallic object. Thus, since metal and the human body are conductive, the electric current of lightning is transmitted to the human body through the metal object. “Depending on the intensity of the lightning and depending on the organs crossed, the passage of electricity in the body can directly or indirectly cause skin burns (ranging from more or less serious superficial burns to necrosis of muscle or bone tissue). ), heart and nervous system disorders (ranging from loss of consciousness to head trauma, even coma with brain damage), organ damage as well as mechanical damage due to violent muscle contractions and falls“, indicates our interlocutor.

Side flash lightning

A person whose feet are in contact with the ground can be struck by lightning. This can happen in particular if the person takes shelter under a conductive structure, such as a tree or a tent, which have themselves been struck by lightning. This is called a “side flash”. Concretely : the difference in electrical potential between the conductor and the head of the individual rises and causes a dielectric breakdown (in other words which does not conduct – or only slightly – electricity but which allows electrostatic forces to be exerted) of the air. The health consequences are the same as those of a direct lightning strike. These accidents can occur outside, but also in a house, through a fixed telephone after the lightning of the external telephone line. This risk of lightning strikes is favored by collective lightning strikes in the open air with propagation from one person to another.

Step voltage lightning strike

A person walking or standing on insufficiently insulated ground can be struck by lightning. This is called a “step voltage” strike. Concretely : lightning strikes the ground and the electric current spreads through the ground, especially around the point of impact. Thus, the electric current very quickly passes through the body of the person or flows on his skin. “Again there is a increased risk of superficial or deep burns (shaped like fern leaves)as well as a risk of cardiac arrestsays Michel Koutmatzoff. Let’s not forget the psychological and neurological complications, which we tend to neglect, because they are invisible and often delayed. Psychological follow-up may be necessary depending on the person’s post-traumatic stress. Indeed, the person struck by lightning may have no memory of the accident or be in a depressed state for months following the lightning strike.

Indirect lightning strike

A person can also have indirect sequelae linked to lightning without having been struck down themselves. These may be traumas related to the fall or the projection of elements affected by lightning, sound traumas related to the noise of lightning (particularly frequent above 120 decibels), ocular lesions due to lightning, gait disorders related to neuromuscular impairment…

Never take shelter under a tree!

When the sky begins to roar, here good habits to adopt :

  • Never take shelter under a tree, especially if the tree is isolated or only part of a small group of trees. The risk of being struck by a lone tree is 50 times higher than that of a standing man.
  • If lightning strikes in the middle of the forest, you must move away from the trunks as much as possible and avoid being close to low branches.
  • In open space such as in a field or in a meadow, do not carry objects – in particular metal, pointed and elongated – above the head such as an umbrella, a pitchfork, a golf club. These so-called “electrically conductive” parts must be lowered or ideally placed on the ground, flat.
  • Do not take shelter under an umbrella.
  • People in groups should keep a distance of at least 3 meters from each other, to avoid the risk of side flash between two people.
  • Move away from all metal structures such as pylons, poles, fences, so as not to be the victim of electrocution by “touch voltage”.
  • Do not stand with your legs apart or walk with long strides when you are in a thunderstorm. The lying position, legs folded in on you, and covered with a raincoat or any insulating plastic material, remains the least risky position.
  • Take shelter in stone huts, in a church, a chapel, or in a closed car (except convertible models, with sunroofs or plastic roofs). On the other hand, it is necessary to avoid taking shelter in a shed which has a sheet metal roof. In this case, remember to fold down or retract the radio aerial.
  • In a house whose interior protection against lightning has not been specially created (even if the house is equipped with a lightning conductor), avoid touching metal parts such as water pipes and taps, as well as machinery. household appliances (washing machine, dishwasher).
  • Do not take a bath or shower during lightning.
  • In the absence of protective devices such as surge arresters, it is strongly recommended to unplug the AC power cord and antenna cable from a television set, and keep them at least one meter away from the set. An unprotected and unplugged television can indeed “implode” during a strong power surge, thus constituting a risk for people in the same room.
  • In the event of a threatening storm, avoid calling with a landline, except in the event of a serious emergency. Prefer mobile phone : its volume, even if it is metallic, remains insufficient to have an attractive effect on lightning.

What outdoor activities should you avoid?

In general, it is better to avoid certain outdoor activities known to be particularly dangerous in stormy weather: fishing, swimming, boating, cycling, golf, mountaineering. Note that water activities are particularly at risk: a wet body is a good conductor of electricity and increases the risk of lightning strikes. Electrical work or roof repairs are also to be banned because they expose you to direct lightning strikes. Before undertaking this type of activity, it is advisable to find out about the weather conditions, for example from Météo France and the national Météorage network.

Person struck by lightning: what to do?

Anyone struck down with certain symptoms such as tingling in the limbs, paralysis of the limbs, amnesia, eye damage, confusion, severe post-traumatic stress, difficulty breathing resembling apnea or loss of knowledge must to be taken to the emergency room. “If you witness a lightning strike, immediately notify the Samu by calling 15 or 112 with a mobile phone“, insists the expert. Take care to indicate to your interlocutors if the victim is conscious, if he is breathing and if you feel his pulse. “Medical help will give you the procedure to follow while waiting for help to arrive and depending on his condition. (cover the person, put them in a lateral safety position, do cardiac massage if they are no longer breathing)”, concludes the specialist.

Thanks to Michel Koutmatzoff, President of the Lightning Protection Association. Interview on July 27, 2019.

Find out more about advice for protection in the event of a storm on the website of the Ministry of the Interior

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