# Do strong magnetic fields have any health effects? **URL:** \ **Category:** Factual Questions\ **Created:** [May 9, 2014, 6:30am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035 "2014-05-09T06:30:54Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![sara20](https://avatars.discourse-cdn.com/v4/letter/s/e79b87/32.png) [@sara20](https://boards.straightdope.com/u/sara20)\ **Post date:** [May 9, 2014, 6:30am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/1 "2014-05-09T06:30:54Z")
I had a couple MRI’s in a short period of time which involve being placed in a giant magnet the size of a dump truck and laying there for a hour. After that I began to experience health problems and hormone problems, as well as night sweats and feeling cold all the time. I am wondering do strong magnetic fields have any negative health effects, especially on hormones? Also can it have any effect on the Hypothalamic–pituitary–adrenal axis. And is it possible that it has health effects we do not know of yet? For example 50 years ago we were told DDT was so safe we can eat it as seen here [DDT so safe you can eat it 1947 - YouTube](https://www.youtube.com/watch?v=gtcXXbuR244) ---
**Author:** ![Batistuta](https://avatars.discourse-cdn.com/v4/letter/b/58956e/32.png) [@Batistuta](https://boards.straightdope.com/u/Batistuta)\ **Post date:** [May 9, 2014, 7:00am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/2 "2014-05-09T07:00:59Z")
Well, a few years ago magnet therapy became ‘a thing’ in Spain. People seemed to think that seeing a doctor who would subject them to strong magnetic fields would be good for their health. A - very reliable - TV programme devoted an entire episode to alternative medicine, and they consulted a - very reliable once again - doctor. The doctor’s response was clear: there is absolutely no evidence in medical literature that magnetic fields can affect our health. That’s a very limited cite though, I’ll wait for actual physicists and doctors to give you a proper answer ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [May 9, 2014, 7:09am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/3 "2014-05-09T07:09:37Z")
Almost certainly no. Millions of people have been having MRI scans for decades now, and so far there has been no indication of any issues. Acute problems like yours would have been flagged very early on had they been correlated with MRI scans. Whilst this sounds a bit harsh, there had to be a reason you needed an MRI - I would start here with any subsequent health issues. At worst, you could have caught something from someone who had been in the scanner prior to you, although I would hope this is unlikely. There is a big difference between DDT and an MRI in terms of causation. One is a poison that we thought was only poisonous to insects. The other is a very strong but static field that has no known physical mechanism to couple to any chemical process, in anything - living or dead. If you could come up with a causative mechanism for a static magnetic field to couple to your body’s processes you would be in line for a free trip to Stockholm. ---
**Author:** ![Fridgemagnet](https://avatars.discourse-cdn.com/v4/letter/f/22d042/32.png) [@Fridgemagnet](https://boards.straightdope.com/u/Fridgemagnet)\ **Post date:** [May 9, 2014, 8:18am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/4 "2014-05-09T08:18:53Z")
This question pops up on a regular basis on the SDMB, and the majority opinion is that only varying magnetic fields can be harmful and static magnetic fields are intrinsically safe. This is dangerous misinformation, and there are regulations all over the world that limit a person’s exposure to static magnetic fields because **STRONG STATIC MAGNETIC FIELDS ARE DANGEROUS!** Just like radiation, UV and X-ray exposure these limits are based upon strength and duration of exposure. MRI scans will fall within these limits, but it’s entirely possible that some people will be more sensitive to exposure than others. A while ago I worked for a company that made big turbogenerators. These used incredibly strong static magnets, and there were very strict health and safety policies in place regarding the handling of these things, even if you didn’t have a pacemaker or a metal plate in your skull. Take your pick of cites: [https://www.google.co.uk/#q=static+magnetic+field+maximum+exposure](https://www.google.co.uk/#q=static+magnetic+field+maximum+exposure) ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [May 9, 2014, 8:53am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/5 "2014-05-09T08:53:38Z")
Reading the guidelines, rather than just citing the existence is a good idea. From The [INTERNATIONAL COMMISSION ON NON‐IONIZING RADIATION PROTECTION, GUIDELINES ON LIMITS OF EXPOSURE TO STATIC MAGNETIC FIELDS](http://www.icnirp.de/documents/statgdl.pdf). > [@](#): > > **Explanation**. > Development of guidelines for static > fields raises two difficult issues. First is the extent, if any, > to which guidelines should allow potential occurrence, in > some exposed workers, of temporary sensory effects with > no known long term or serious consequences. Second is > the extent to which restrictions should prevent levels of > exposure higher than those for which there is human > experience hence for which there is no known adverse > effect but a concern about lack of knowledge. With > regard to the first issue, ICNIRP considers that there are > occupational circumstances where, with appropriate ad- > vice and training, it is reasonable for workers voluntarily > and knowingly to experience possible transient sensory > effects such as nausea, since they are not believed to lead > to long term or pathological health effects. **With regard to > the second issue, ICNIRP considers that the exposures > permitted under the guidelines should be based on levels > for which there is appreciable evidence, and should not > go higher than this merely because of lack of evidence of > adverse effects.** In other words, they have set the guidelines at a point where they know it is safe, and have not gone higher, not because there is evidence it becomes unsafe, but simply because there has been no experimentation at all at these levels. Given the levels are already higher than found in MRI scanners anyway, the idea that there are known dangers in MRI scanners is actually not supported. OH&S guidelines for large permanent magnets are going to be very much about not letting the thing kill you by getting too close to anything ferromagnetic. The field strength of these magnets is actually much less than an MRI scanner. ---
**Author:** ![mdcatdad](https://avatars.discourse-cdn.com/v4/letter/m/58f4c7/32.png) [@mdcatdad](https://boards.straightdope.com/u/mdcatdad)\ **Post date:** [May 9, 2014, 9:47am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/6 "2014-05-09T09:47:17Z")
> [@Batistuta](#): > > Well, a few years ago magnet therapy became ‘a thing’ in Spain. People seemed to think that seeing a doctor who would subject them to strong magnetic fields would be good for their health. > > A - very reliable - TV programme devoted an entire episode to alternative medicine, and they consulted a - very reliable once again - doctor. The doctor’s response was clear: there is absolutely no evidence in medical literature that magnetic fields can affect our health. > > That’s a very limited cite though, I’ll wait for actual physicists and doctors to give you a proper answer When challenged, the alt med crowd will mumble something about the iron in your blood, but the iron in human blood isn’t concentrated enough to respond to a magnetic field, especially the weak “therapeutic” magnets sold by the quacks ---
**Author:** ![Fridgemagnet](https://avatars.discourse-cdn.com/v4/letter/f/22d042/32.png) [@Fridgemagnet](https://boards.straightdope.com/u/Fridgemagnet)\ **Post date:** [May 9, 2014, 9:57am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/7 "2014-05-09T09:57:03Z")
> [@Francis Vaughan](#): > > …a very strong but static field that has no known physical mechanism to couple to any chemical process, in anything - living or dead. > [@ICNIRP courtesy of Francis Vaughan](#): > > ICNIRP considers that there are occupational circumstances where, with appropriate advice and training, it is reasonable for workers voluntarily and knowingly to experience possible transient sensory effects such as nausea, since they are not believed to lead to long term or pathological health effects. Which is it? There’s plenty of documented evidence of strong static magnetic fields causing disorientation, nausea and hallucination, although thankfully there’s nothing on Earth that would cause instant death (but don’t get too close to a [magnetar](http://solomon.as.utexas.edu/~duncan/magnetar.html)). I’d agree that there’s no evidence that MRI scans have adverse long-term effects, but it’s just not true that static magnetic fields have no effect on the body. Even if the effects are transient, you don’t want to be driving or operating heavy machinery while disoriented, nauseous or experiencing sensory distortion. I’d class that as dangerous. I’m not getting into a pissing contest; over and out. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [May 9, 2014, 10:03am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/8 "2014-05-09T10:03:27Z")
An [article](http://www.who.int/peh-emf/publications/facts/fs299/en/) from WHO on magnetic fields and health. > [@](#): > > For static magnetic fields, acute effects are only likely to occur when there is movement in the field, such as motion of a person or internal body movement, such as blood flow or heart beat. A person moving within a field above 2 T can experience sensations of vertigo and nausea, and sometimes a metallic taste in the mouth and perceptions of light flashes. Although only temporary, such effects may have a safety impact for workers executing delicate procedures (such as surgeons performing operations within MRI units). > > Static magnetic fields exert forces on moving charges in the blood, such as ions, generating electrical fields and currents around the heart and major blood vessels that can slightly impede the flow of blood. Possible effects range from minor changes in heartbeat to an increase in the risk of abnormal heart rhythms (arrhythmia) that might be life-threatening (such as ventricular fibrillation). However, these types of acute effects are only likely within fields in excess of 8 T. > > It is not possible to determine whether there are any long-term health consequences even from exposure in the millitesla range because, to date, there are no well-conducted epidemiological or long-term animal studies. Thus the carcinogenicity of static magnetic fields to humans is not at present classifiable (IARC, 2002). So, immediate bad effects can happen, but at levels higher than you find in an MRI. And no one really knows about low level fields. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [May 9, 2014, 10:43am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/9 "2014-05-09T10:43:21Z")
The issue with sensory effects is that moving in the field can and will induce an electric current in you. The linked to standard covers this in detail. This electric current can disturb your sense of balance leading to dizzyness, and eventually possibly nausea. It is about as dangerous as (and has a lot in common with) spinning around to make yourself dizzy. (Don’t drive a forklift after doing either.) What it isn’t, is a static magnetic field to chemical interaction with your biology. There is a serious bottom line here about perception of effects risk, and causation. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [May 9, 2014, 11:40am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/10 "2014-05-09T11:40:46Z")
DDT still IS safe enough to eat. It wasn’t banned for being dangerous to humans. ---
**Author:** ![ouryL](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ouryl/32/6067_2.png) [@ouryL](https://boards.straightdope.com/u/ouryL)\ **Post date:** [May 9, 2014, 7:59pm UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/11 "2014-05-09T19:59:22Z")
> [@sara20](#): > > I had a couple MRI’s in a short period of time which involve being placed in a giant magnet the size of a dump truck and laying there for a hour. After that I began to experience health problems and hormone problems, as well as night sweats and feeling cold all the time. I am wondering do strong magnetic fields have any negative health effects, especially on hormones? Also can it have any effect on the Hypothalamic–pituitary–adrenal axis. And is it possible that it has health effects we do not know of yet? For example 50 years ago we were told DDT was so safe we can eat it as seen here [https://www.youtube.com/watch?v=gtcXXbuR244](https://www.youtube.com/watch?v=gtcXXbuR244) I will presume you got these because you weren’t experiencing optimal health? ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [May 10, 2014, 2:37pm UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/12 "2014-05-10T14:37:06Z")
How fast are the magnetic fields changing in an MRI, compared to transcranial magnetic stimulation? Why don’t MRIs have the same effect? ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [May 10, 2014, 4:43pm UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/13 "2014-05-10T16:43:52Z")
The main field of an MRI scanner is static. When operating there are gradient coils that cause slight variations in the field across the volume being scanned (hence the term gradient.) These are very low power in comparison to the static field - and are created by ordinary electro magnets - not superconductors. They do however account for the noise - they act a lot like the voice coils of a speaker inside, and rattle. Some of the early research MRI scanner actually used HiFI amplifiers to drive the gradient coils. Something that gives you an idea of the relative field strength. (The Q of a proton in the static field is very very high, which means only very slight changes in the field result in relatively high changes in frequency of precession, so the gradient could really don’t need to produce much power. TMS creates a very high power and fast moving field. You need to discharge a bank of capacitors into a carefully crafted very focussed coil. The instantaneous field generated is very high. Orders of magnitudes higher than that generated by the gradient coils in an MRI scanner. You would no more get a TMS like effect from an MRI scanner than from waving a small magnet next to your head. ---
**Author:** ![sara20](https://avatars.discourse-cdn.com/v4/letter/s/e79b87/32.png) [@sara20](https://boards.straightdope.com/u/sara20)\ **Post date:** [May 10, 2014, 6:00pm UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/14 "2014-05-10T18:00:08Z")
> [@sara20](#): > > I had a couple MRI’s in a short period of time which involve being placed in a giant magnet the size of a dump truck and laying there for a hour. After that I began to experience health problems and hormone problems, as well as night sweats and feeling cold all the time. I am wondering do strong magnetic fields have any negative health effects, especially on hormones? Also can it have any effect on the Hypothalamic–pituitary–adrenal axis. And is it possible that it has health effects we do not know of yet? For example 50 years ago we were told DDT was so safe we can eat it as seen here [https://www.youtube.com/watch?v=gtcXXbuR244](https://www.youtube.com/watch?v=gtcXXbuR244) I seem to recall that Dr. mercola said that magnetic fields had negative health effects and to avoid them but don’t remember why, does anyone have the scoop on what he said? ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [May 10, 2014, 6:06pm UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/15 "2014-05-10T18:06:09Z")
> [@sara20](#): > > I seem to recall that Dr. mercola said that magnetic fields had negative health effects and to avoid them but don’t remember why, does anyone have the scoop on what he said? Doesn’t matter, the man is a fraud. Note that one side says that magnetic fields are harmful while the other side peddles magnet based therapies of one form or another. ---
**Author:** ![Elemenopy](https://avatars.discourse-cdn.com/v4/letter/e/b5e925/32.png) [@Elemenopy](https://boards.straightdope.com/u/Elemenopy)\ **Post date:** [May 10, 2014, 6:32pm UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/16 "2014-05-10T18:32:00Z")
Just throwing this out there: [TMS therapy is FDA approved](http://www.hopkinsmedicine.org/psychiatry/specialty_areas/brain_stimulation/tms/) and is similar in some ways to an MRI. It is thought to be able to cause seizures as a rare side effect, but is well tolerated and can be of help to people with treatment-resistant depression. [This study](http://onlinelibrary.wiley.com/doi/10.1002/ana.410400306/abstract;jsessionid=E72EA8AA3E9BE08DF34551BEC2FB2744.f03t03?deniedAccessCustomisedMessage=&userIsAuthenticated=false) indicates that various antiepileptic drugs can influence a person’s motor/neuronal excitability when exposed to the magnetic pulses of TMS. While I can’t address the OP’s questions specifically, I’d have to say that there is at least some reason to explore long term effects of MRI exposure. TMS therapy is not considered “woo” by many psychiatrists, at any rate. Anecdotally, I’ve found MRI imaging to be soothing. It may be just the environment. ---
**Author:** ![Elemenopy](https://avatars.discourse-cdn.com/v4/letter/e/b5e925/32.png) [@Elemenopy](https://boards.straightdope.com/u/Elemenopy)\ **Post date:** [May 10, 2014, 11:58pm UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/17 "2014-05-10T23:58:19Z")
:smack: I don’t know how I missed the posts above mine discussing TMS… I enjoyed the explanation, Francis Vaughan. I wasn’t sure of the technical differences between the two–I’ve only seen that the mechanisms are “comparable.” ---
**Author:** ![sara20](https://avatars.discourse-cdn.com/v4/letter/s/e79b87/32.png) [@sara20](https://boards.straightdope.com/u/sara20)\ **Post date:** [June 19, 2014, 8:12am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/18 "2014-06-19T08:12:56Z")
Just wanted to add some new info I discovered about MRI’s from wikipedia "Genotoxic effects There is no proven risk of biological harm from even very powerful static magnetic fields.[56][57] However, genotoxic (i.e., potentially carcinogenic) effects of MRI scanning have been demonstrated in vivo and in vitro,[58][59][60][61] leading a recent review to recommend “a need for further studies and prudent use in order to avoid unnecessary examinations, according to the precautionary principle”.[57] In a comparison of genotoxic effects of MRI compared with those of CT scans, Knuuti et al. reported that even though the DNA damage detected after MRI was at a level comparable to that produced by scans using ionizing radiation (low-dose coronary CT angiography, nuclear imaging, and X-ray angiography), differences in the mechanism by which this damage takes place suggests that the cancer risk of MRI, if any, is unknown.[62]" Genotoxic means it apparently causes DNA damage If MRI’s cause DNA damage would that explain some of the health problems I received from having multiple MRI’s within a short period? ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [June 19, 2014, 8:26am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/19 "2014-06-19T08:26:17Z")
> [@sara20](#): > > Genotoxic means it apparently causes DNA damage > > If MRI’s cause DNA damage would that explain some of the health problems I received from having multiple MRI’s within a short period? No. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [June 19, 2014, 9:59am UTC](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035/20 "2014-06-19T09:59:25Z")
This is what the NHS website has to say about it: > [@](#): > > Extensive research has been carried out into whether the magnetic fields and radio waves used during MRI scans could pose a risk to the human body. No evidence has been found to suggest that there is a risk, which means that MRI is one of the safest medical procedures currently available. [http://www.nhs.uk/conditions/mri-scan/pages/introduction.aspx](http://www.nhs.uk/conditions/mri-scan/pages/introduction.aspx) [Next page](https://boards.straightdope.com/t/do-strong-magnetic-fields-have-any-health-effects/688035.md?page=2)