Electrical Injury and Electric Shock
(Information for the injured and the interested)
Michael S. Morse, Ph.D.
If you have arrived at this page, it is not unlikely that you are the victim of an electrical contact and you have come here looking for answers to many seemingly unanswerable questions. We get many emails and calls from individuals who are suffering from the long term effects of an electrical contact and have been told that their symptoms are just not possible. Before you read further, I will tell you that electrical injury can manifest in many forms and with many symptoms. Even household (sometimes called low voltage) contacts can have a devastating impact on one's health and life.
If you have been told that your symptoms don't make sense, raise your hand now…
Let’s not blame the medical community too much. Electrical injury is widely misunderstood but for some very good reasons. The biggest reason is that the field has completely changed since 1990 and most physicians (and most informational sources) have not yet caught up with those changes. Physicians are busy folks. Some responses to electrical contact are so rare that the typical doctor might never see such a case except by scouring the literature much of which is relatively new.
When electricity was a new technology:
We have been using commercial electricity in this country since the late 19th century and much of our earliest knowledge was gleaned from anecdotal reports of electrical injury. True scientific characterization of human response to electricity came of age in the last half of the last century. We quickly came to know that electricity is dangerous stuff. Almost as quickly we came to know that the benefits of properly used electricity far outweigh the risks. You need not be a scientist to know that more people live with it than are killed or injured by it.
The early research:
Research in the mid-twentieth century by a man named Charles Dalziel set the standards for our understanding of electrical injury. To those who have not kept up with the latest research, these standards may also be used to define the boundaries for injuries that can be caused by electricity. Read on and you will see that such a belief is unfortunately quite flawed.
The early research gave us a table of human responses to electricity (shown below with information from work by Dalziel and others) that was widely believed to be the definitive statement about electrical contact. As a matter of fact, up until near the end of the twentieth century it pretty much was. The problem with this table is that it crams a large amount of information into a few very generalized representations. Rather than being cut in stone, the table of human responses should best be looked upon as a starting point for analyzing any electrical contact. Each electrical contact should be considered in light of its similarities and differences to the information represented in the table. To truly understand any electric shock, one must understand much more about human interaction with electricity than the information found in the table of human responses.
Human Response to Electrical Contact
Current level (Approximate average values)
Sensation - tingling (first perception)
|Painful shock but no loss of muscle control||9 milliamps|
16 milliamps for males (10 milliamps for females)
Painful muscle contraction/difficulty breathing
50 milliamps (hand to hand contact)
Myocardial sustained contraction
Greater than 1 ampere (>1000 milliamps)
Burns (Thermal Injury
Greater than 1 ampere (>1000 milliamps)
Shortcomings of the Table of Human responses to electrical contact:
First and most important is that the table fails to recognize human variability. We are incredibly variable machines. What may not even phase one person may kill another or cause lifelong disability for a third. The research that created this table, highlights the extent of human variability unfortunately, that information is lost in the simplicity of its presentation in a single table.
Second, the information in the table has lost the context of electrical path (current path between entry and exit points of the electricity) and shock duration (time of contact), both of which have immense impact on the injury from any contact. Some versions of this table do in fact have footnotes that explain these boundaries. The representations so often quoted and reprinted represent an average for 3 second hand-to-hand contacts for 70 kg males. Much of the data is also extrapolated from animal studies.
Third, this table compares electrical apples and oranges. It contains information about sensation as well as effects on the heart. Even with human variability, sensation is somewhat of an absolute but effects on the heart are very random. As a generalization, if the shock did not kill you, (even if the shock was greater than 50 milliamps hand to hand), it did not fibrillate your heart. The truth is that if everyone who received a 50 milliamp or larger shock suffered ventricular fibrillation, almost every weekend garage hobbyist would probably die eventually from an electric shock. Research suggests that the risk of fibrillation is linked to the duration of the shock and the phase of the heart. There are many variables that influence how or if the human heart is impacted by any given electrical contact.
Typical Electrical Injury:
Human response to electrical contact is widely varied. Injuries from electric shock may be thought of as either primary or secondary.
Primary injuries occur because current has passed through the body and has had an impact on the tissues. Primary injury is usually related to the amount of electrical energy of the shock. (Energy will be discussed later.) Energy is necessary to heat the tissues. If tissues heat enough, they will be damaged or burned. Most heating typically occurs at the skin surface but some may occur within the body, especially with high voltage or long duration shocks. Since electricity can cause muscles to contract beyond the ability to let-go of the source of the electricity, it is possible to become attached to even a household electric circuit and receive a shock of significant duration and thus significant energy. Any tissue in the body traversed by the current can in fact be subject to thermal injury. With household current, internal thermal injury is rare but does occur. Nerve injury is a common primary response to many, even brief shocks.
Secondary injury can result when one struggles to get away from the source of the shock (as is the very typical human response.) If one's muscles are forcefully contracted by the electricity and they cannot let-go from the source of the electric current, there is typically an overwhelming effort made to break free. The result of such an effort can be seen in soft tissue injury and tears and in some cases, even in broken bones.
In summary, the typical electrical injury may be characterized as being burns caused by electrical tissue heating with most likely injury at the skin surface. Secondary injuries from trying to escape the source of the current follow when one is drawn into the area of the shock by involuntary muscle contraction.
Ventricular Fibrillation from Electrical Contact:
As with any other tissues that the current may touch, the heart is affected by electricity. Electrical current that traverses the heart can interfere with the heart's rhythm and cause the heart to fibrillate which will lead to death absent proper and immediate medical intervention. The good news is that if one's heart did not fibrillate as the immediate result of the shock, the likelihood of future fibrillation decreases fairly rapid with time. (NOTE: This is not an absolute and prudent treatment always involves a period of observation and EKG monitoring.)
Atypical Electrical Injuries:
The rest of this page will deal with myths and atypical responses to electrical contact. It is the atypical response that requires the most study and analysis so as to understand the effects that are linked to the electricity. It is also, the atypical response that is least understood.
Myths and mysteries about electric shock explained:
1. It is the current not the voltage that causes injury:
Absolutely true but it just is not that simple.
Voltage is directly linked (and proportional) to current by Ohm’s law which says that Current = Voltage divided by Resistance (I=V/R). This is more often stated as V=IR.
Voltage is the voltage drop between the entry and exit points.
Resistance is the resistance between the entry and exit points. Human resistance can vary wildly. Our skin was designed to be a barrier to the flow of electricity but when it gets wet it no longer protects and serves. For shocks in very wet environments skin resistance can drop to only a few hundred ohms while in very dry environments, skin resistance can come up to hundreds of thousands of ohms. (As a sidenote, many experts like to use a compromise value of 1000 ohms as typical human limb to limb resistance.)
So, it is true that it is the current that causes the injury and it takes more voltage to drive the same current through dry skin versus wet skin but for all practical purposes, voltage and current are forever linked.
Research Fact: Modern research in electrical injury has shown that some of the most perplexing injuries are not linked to either voltage or current.
2. No burns, no injury:
Another great myth.
Most electrical burns occur because of high tissue (skin) resistance at the entry or exit points of the current. This is coupled with high current density because all of the energy of the contact is focused at a small area of electrical entry or exit. Lots of energy focused on a single point = burns.
Throw a little moisture in the mix and/or spread out the current entry over a wider area and you can have one whopping big shock with no indication that it ever occurred.
Research Fact: Not to get too scientific but this is proven by statistics that show that almost half of all household voltage shocks yield no entry or exit wounds.
3. Electrical injury is all about the energy put in the body during an electrical contact:
Close but not quite true.
Think of energy as the total amount of electricity that one receives during an electrical contact. More energy certainly does mean more risk of injury but it does not define the limits of the injury from electricity.
Energy = (Power x duration of contact) where Power = (Voltage x Current)
Energy = Voltage x Current x duration of the contact
Energy is big in considering electric shock. Thermal wounds (burns) both internally and externally are the function of the energy of the shock. What this says, is more voltage (which we all now know means more current) and more time = more energy. More energy means more heating and more heating means more injury.
Heating however is not the only way that tissues are injured by electricity so read on.
Up until the end of the twentieth century, we could stop here but there is so much more that has just been discovered.
4. The path followed by the current limits the location of the injury:
The theoretical current pathway is the shortest line between entrance and exit points of the electric current.
Well, if the theoretical current path adhered to the laws of physics it would be great thing, but it doesn’t … well almost doesn’t.
The broad theory says the body should be treated like a “structureless gel” and that current follows the shortest point from entry to exit. As a result, the only injuries that can occur will occur on or near that line since the only energy imparted to the body is on or near the theoretical current line.
Bah humbug! (That is right, you heard it here… Bah humbug.)
Way too many electrical injuries manifest symptoms remote to the theoretical current path so there must be a problem with this theory.
Problem 1. Anyone who has ever seen the inside of a body knows that it is not a structureless gel. It turns out that we are full of stuff that conducts electricity in different amounts and different ways.
Problem 2. The structureless gel theory violates an extension of Ohm’s law. Ohm's Law says that current will flow in all pathways but in inverse proportion to the resistance of the pathway. Electrical engineers know this as the current divider rule. An absolute about the flow of current in any circumstance is that current will go through any conductive path but most of it will go where it is easiest to go (path of least resistance) and some of it will go through paths of higher resistance and almost none of it will go through paths of very high resistance. None of it will flow through paths that are insulators.
In the human body, low resistance paths tend to be both the shortest paths and also the paths that include bulk tissues like muscle and high conductive tissues like fluids and nerves. Things like bones tend to be very poor conductors of electricity.
So, the structureless gel theory almost works. I even have research to prove it.
It is certainly possible that the imperfections in the theory may explain a lot of the unexplainable injuries from electricity.
5. If pathway and energy don't explain the injury then the symptoms must be imagined:
There is just too much evidence that many of the same "unexplainable" symptoms occur in too many independent instances to be imagined. That is of course unless a lot of people around the world are imagining the same responses to electrical contact independent of each other.
One very promising explanation is something called “Electroporation” which in short says that a high electric field will punch holes in some cells and cause injury.
OK, back to English now.
A high electric field means a large number of volts per inch. (Divide the voltage between entrance and exit by the distance between electric entry and exit points and you have the electric field… sort of.)
Lets try to understand the concept.
If you bite into a power cord (which is an incredibly bad idea) the entrance and exit points will be spaced by only a fraction of an inch and the electric field could approach 1000 volts per inch. If you have the same voltage shock that goes between your left and right hand (with spacing of around 72 inches), the electric field may be just volts per inch.
Electroporation probably only applies in very high voltage shocks or shocks where the entry and exit points are very very close together. In any case, injury from electroporation can only occur along the current path so we still have not explained all those other injuries.
What do we know about those injuries that produce symptoms that somehow defy explanation?
Welcome to the 21st century understanding of electric shock.
Research has shown that there is a rare class of electrical injury that was pretty much unknown until recently. In fact, it is so rare that most physicians will never see a case in their career. This class of electrical injury defies explanation by all prior theories. Still we know with scientific certainty that it exists.
How do we know you ask?
Well, thank science (and Al Gore) for the World Wide Web. Prior to the 1990’s few researchers were really able to study unexplainable symptoms following electrical contact. The problem was that it was almost impossible to get enough subjects in any one place to conduct a valid study. As a young researcher and consultant, I (along with others) in the field began to notice the occasional case where the symptoms from the shock did not follow from the parameters of the shock. Symptoms were not explainable by any currently accepted theory of electrical injury. Yet, there they were.
Was it possible that all those people in this growing population from which we were gathering data were liars, crazy, or malingerers?
Forget being a crazy optimist who believes in the honesty of the average human, I am also one who believes in the validity of valid statistics. If you get enough people together with common electrical contact scenarios and you look at the commonality among the symptoms that follow and then do some statistical magic, out pops the only conclusion that one can reach as a scientist... there must be an unexplained class of electrical injury that occurs in some small and random number of electrical contacts.
Symptoms reported by those who manifested this type of response to electrical contact were:
Not proportional to the energy of the shock
Not related to the voltage of the contact
Not related to the duration of the contact
Not related to the theoretical path of the current
In some cases, the symptoms sounded pretty darn extreme if not ridiculous because all the literature back then said that such symptoms were just not possible.
The problem was that people around the country and the world were suffering the same set of symptoms. Absent a tool like the World Wide Web by which these people could find each other, no one seemed to really knew that they existed as a common population. Once brought together, it became apparent that there exists a very rare class of electrical injury that must be the result of some as of yet unexplained injury to the body caused by electrical contact. (Remember, we are pretty darn complex machines and our ability to understand ourselves is really in its infancy.)
We have come to describe this class of injury using the term Diffuse Electrical Injury (DEI).
What is Diffuse Electrical Injury?
Diffuse Electrical Injury (also called in the literature by a variety of other names such as electric shock syndrome or post electric shock syndrome), is an injury to the human body following an electrical contact where the body response is often neither proportional to the parameters (voltage, current, or duration) of the shock nor is the tissue response limited to the theoretical current pathway. The manifestations of DEI are an assortment of path related physical symptoms (tingling, weakness to name just two) and remote symptoms where the remote symptoms can be of either a physical or neuropsychological nature (general fatigue, broad diffuse pain, personality changes, depression, short term memory loss to begin the list.) The fingerprint for DEI consists of these symptoms taken in the context of the chronology of their occurrence.
Do we know the mechanism of Diffuse Electrical Injury?
Sadly, we do not but I suspect that it is only a matter of time before research ultimately finds other mechanisms of injury from electricity that serve to explain the symptoms.
Do we know if DEI (or any of its fine aliases) really exists:
Yes we do.
Multiple researchers including ourselves have been studying this broad array of symptoms found in these many individuals who are for the most part geographically isolated from each other. The scientific literature from multiple researchers now recognizes that there is in fact a common set of symptoms among many who have suffered from what might best be classed as a rare type of electrical injury.
So, what is the problem?
This injury still flies under the diagnostic radar of modern technology.
Ego often won’t let scientists and medical practitioners acknowledge that things exist that have not yet been explained or cannot yet be seen. Imagine all the diseases that were unexplained before the advent of such incredible technologies as x-rays, CAT scans, MRIs etc. It is hopefully only a matter of time.
Without imaging and without knowledge of the mechanism, we know the injury exists because the statistics and the scientifically accepted literature says that it exists. Just because we have not yet developed the technology to image it and we have not yet learned enough about the human machine to explain it does not make it something of a purely imagined nature. That which we cannot see, we must not disregard or we may be destined never to see it.
If you suffer from this class of injury, know two things:
First you are not alone
Second, science is always advancing. There is hope for the future.
For more information on electrical injury and to request scientific literature click on the the request literature tab.