What Magnetic Fields Do to Your Brain and Body

By Erica Tennenhouse | May 25, 2018 11:39 am
(Credit: pippeeContributor/Shutterstock)

(Credit: pippeeContributor/Shutterstock)

There’s no escaping magnetic fields—they’re all around us. For starters, the Earth itself is like a giant magnet. A spinning ball of liquid iron in our planet’s core generates the vast magnetic field that moves our compass needles around and directs the internal compasses of migrating birds, bats, and other animals. On top of that, ever-industrious humans have produced artificial magnetic fields with power lines, transport systems, electrical appliances, and medical equipment.

We may not be able to see, hear, feel, or taste the magnetic fields that surround us, but some may wonder whether they can still exert effects on our bodies and brains. This question becomes more pertinent, and the answers more tantalizing, as the strength of the magnetic field in question gets cranked up.

Everyday Exposure

A magnetic field arises whenever a charged particle, like an electron or proton, moves around. Since the electric currents running through blenders, hairdryers, and wires in the walls of our homes consist of flowing electrons, they all generate magnetic fields. Through these sources, the average person is exposed to magnetic fields reaching 0.1 microtesla in strength on a daily basis. By comparison, the Earth’s magnetic field, which we are always exposed to (as long as we remain on the planet’s surface), is about 500 times stronger. That means the magnetic force penetrating your body as you lounge around your home or spend a day at the office is decidedly insignificant.

From time to time, a scientific study finds a link between living near high-voltage power lines and illness. Heightened risk of childhood leukemia is the most commonly cited potential health consequence, but whether or not the risk is real has been hard to pin down. One glaring issue is that scientists have yet to figure out the mechanism by which such weak magnetic fields—which are still in the microtesla range for homes next to power lines—could adversely affect the human body. In 2010, the International Commission on Non-Ionizing Radiation Protection concluded that the evidence that living near power lines increases the risk of the deadly blood cancer “is too weak to form the basis for exposure guidelines.”

(Credit: VILevi/Shutterstock)

An MRI machine. (Credit: VILevi/Shutterstock)

What’s the Threshold?

Meanwhile, a team of scientists at the Utilities Threshold Initiative Consortium (UTIC) has been busy working to figure out the threshold at which the human body shows a physiological response to a magnetic field. According to Alexandre Legros, a medical biophysicist at the Lawson Health Research Institute and Western University in London, Ontario and a UTIC scientist, the smallest magnetic field that has reliably been shown to trigger a response in humans is around 10,000 to 20,000 microtesla. But crucially, to produce the effect, the field cannot be static like Earth’s magnetic field; rather, it must change directions over time. When these strong, direction-shifting magnetic fields get directed at a human, small electrical currents begin to pulse through the body. Above that threshold, the currents can stimulate super-sensitive cells in the retina, known as graded potential neurons, giving the illusion of a white light flickering even when the affected person is in darkness; these visual manifestations are known as magnetophosphenes.

The 10,000-microtesla threshold is well above the strength of any magnetic field encountered in everyday life. So in what situations might magnetophosphenes occur?

Medical Magnets

“There’s only one circumstance in which you may perceive magnetophosphenes,” says Legros: “If you’re in an MRI [magnetic resonance imaging] machine and moving your head fast.” An MRI scanner is essentially a big magnet that produces a powerful magnetic field of around 3 tesla (or 3 million microtesla) — millions of times larger than the fields we’re normally exposed to. But because it’s a static magnetic field, MRI scanners don’t exert any noticeable effect on the body. That would change, however, if the patient inside the scanner were to rapidly move his or her head back and forth. “Moving quickly induces a time-varying field, so by doing that you are inducing currents in different structures of your brain,” says Legros. Those currents may lead to nausea, loss of balance, a metallic taste in your mouth, or in some cases, magnetophosphenes.

On par with the magnetic field of an MRI is the one produced by a medical procedure known as transcranial magnetic stimulation (TMS). But unlike MRI, which makes detailed pictures of the inside of the body, the purpose of TMS is to stimulate the brain. That task requires an electric current, which is why TMS relies on a magnetic pulse rather than a static magnetic field. When this pulse is delivered via an electromagnetic coil placed against the scalp, the resulting current jolts a particular part of the brain with the aim of treating neurological diseases like depression.

Out-of-this-World Magnetic Fields

The magnetic fields associated with MRI and TMS are the strongest that a human might realistically be exposed to. Still, they are “hilariously puny” compared to those found beyond our planet, says Paul Sutter, an astrophysicist at Ohio State University and chief scientist at the COSI Science Center in Columbus, Ohio. At the extreme lies the aptly-named magnetar, which is a rare type of neutron star with a magnetic field one thousand trillion times stronger than Earth’s.

An artist's impression of a magnetar. (Credit: ESO/L. Calçada/Wikipedia (CC BY 4.0))

An artist’s impression of a magnetar. (Credit: ESO/L. Calçada/Wikipedia (CC BY 4.0))

If any human ever got close to a magnetar, they would quickly find themselves in dire straits. “Strong magnetic fields can start to do surprising things,” says Sutter. At the atomic level, the strong magnetic field would move all of the positive charges in your body in one direction and the negative charges the other way, he explains; spherical atoms would stretch out into ellipses and soon they would start to resemble thin pencils. That drastic change in shape would interfere with basic chemistry, causing the normal forces and interactions between atoms and molecules in the body to break down. “The first thing you would notice is your entire nervous system, which is based on electrical charges moving throughout your body, is going to stop working,” says Sutter. “And then you basically dissolve.”

Sutter guarantees that our local neighborhood — which he defines as a radius of a few hundred light-years around Earth — has been surveyed and certified magnetar-free. None of these exotic objects are approaching us, and none of the massive stars nearby are likely to turn into magnetars when they die. The nearest magnetar is a safe distance of tens of thousands of light-years away. So, at least for the time being, we can rest easy and take comfort in our planet’s own meager magnetic field.

CATEGORIZED UNDER: Environment, Health & Medicine
  • OWilson

    We, and everything around us, is composed of positively charged protons, and negatively charged electrons.

    We are surrounded by an almost infinity of electromagnetic fields from cell phones, all electrical appliances and even space itself.

    It is hard to imagine that those fields have no effect on the body or the brain.

    But are human lifespans are increasing most where those appliance are used most?

    “More study needed!” :)

    • Ana Beatriz


    • Cee Betterchoice

      I disagree. This article makes a compelling case for the insignificant levels of the magnetic fields we generate. Your concern seems to be based on an emotional response, not one based on any empirical foundation.

      • OWilson

        I personally have no emotional concern with everyday EMFs.

        My basis for that is actually very personal empirical observation. :)

        In a former life, I was involved in land compensation resolution issues with NIMBY residents opposing a new electrical power transmission line on the edge of their residential subdivision.

        There opposition was based on reduced property values and EMFs which were currently under scrutiny at the time.

        We agreed property values could be affected by the visual aspect of these lines, and compensation offered, including the option to re-locate at no expense. and in addition a generous disturbance allowance which would allow them to actually upgrade their current housing.

        The issue of EMFs was resolved by a small hand held EMF monitoring device.

        I took the most vocal of the objectors to an adjacent power corridor and we measured the strength of the radiation, under, and at various short distances from the power lines.

        Them I took the same meter into their houses and we checked the ambient EMFs from their appliances, including the old CRT TVs. computer, electric stove, washers dryers, and microwave ovens etc.

        It was no contest!

        Eventually they all signed up for the very generous compensation, nobody left, and the line is now sending electricity down the line to their neighbors who can share the same electrical amenities that they themselves enjoy.

        After all, their own electricity, phone, cable, cell phone facilities, internet, gas, water and sewer lines came across other people’s land, and if everybody said no, where would modern society be? :)

    • Jeffrey Millinger

      more study needed for you… for those of us who have studied, we already know the answers.

  • Not_that_anyone_cares, but…

    Indeed “…living near power lines increases the risk of the deadly blood cancer…”

    But then consider that just ‘…living n̶e̶a̶r̶ ̶p̶o̶w̶e̶r̶ ̶l̶i̶n̶e̶s̶ increases the risk of the deadly blood cancer…’

    • OWilson

      Years ago there were a lot of studies purporting to show that living near transformers ans sub stations posed a hazard to health.

      The correlation was clearly there, but it turned out that folks who were forced by poor economic circumstance to live in the mainly industrial areas where these ugly facilities were often sited, had other local health hazards as well, pollution, even lifestyle choices.

      The correlation was there, but it was difficult to pin down the cause to measurable EMF’s that drop off sharply with distance to the point where a modern household with a full suite of appliances can actually show higher readings of EMF.

      Correlation is not cause, but can serve as a convenient scapegoat for impatient social engineers. :)

      • Brian Wilson

        I appreciate your comments on this topic. it shows both intelligence and thoughtfulness.

        • OWilson

          Thank you! I don’t think we are related! :)

          My views come from a lifetime of interest in my favorite areas of science, politics, and the human condition, in 6 disparate countries I’ve had the good fortune to live in!

          In other words. old age! :)

  • https://johnthimakis.wordpress.com/ John Thimakis

    “and then you would basically dissolve”.
    Sounds worse than encountering a black hole.

  • PhishPhace

    I once saw a movie of a frog being levitated in a magnetic field. Didn’t seem to hurt it. However, considering we are exposed to magnetic and electromagnetic fields a billion times stronger than natural background; it makes one wonder what the long term effects are.

  • Christmas Snow

    The effect of magnetism on the body is interesting. There is a new field of chemistry and biochemistry under strong magnetic fields, awaiting discovery.


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