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Medical What's the strongest magnetic field safe for humans?

  1. May 27, 2010 #1
    Hi all!
    I'm a neuroscience major and I'm planning my senior honors thesis right now. I'm interested in magnetoreception (ability to sense magnetic fields), and I'd like to do something involving the effect of a strong magnetic field on humans' or animals' navigational abilities and/or behavior. Basically, I'd love to use humans ... but I'm not sure if I can safely expose people to a >1 Tesla B field. I know that really strong magnetic fields can disrupt electrical firing in the brain ... or is that only magnetic pulses? Anyway, does anyone know how strong of a field I can use? Or if I need to already be an MD to do it?

    Also, if I can't use humans, what would be a good animal to test? I can't find a comprehensive list of which animals have already been shown to have magnetoreception and which animals are yet to be tested. I'm thinking lower mammals would be great. Anybody have any suggestions for me? Thanks!
  2. jcsd
  3. May 27, 2010 #2
    I recall reading somewhere that someone has recently built an 11T human MRI.

    Magnetic fields by themselves are not dangerous, but rapidly changing magnetic fields can be.
  4. May 27, 2010 #3
    Right, rapidly changing magnetic fields would create flux. But wouldn't even an unchanging magnetic field move ions in the brain?
  5. May 27, 2010 #4
    Not at any static field strengths you would be likely to achieve. (Unless you have an unlimited budget).
  6. May 28, 2010 #5


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    Shall I assume you have already made a comprehensive search in your college library and the web of magnetoreception? If you have, you may notice that organisms that do respond to the earth's magnetic field (assisting navigation) don't require very much magnetic field (30-60uT) to do so. What is your reasoning for choosing a strong magnetic field?
  7. May 28, 2010 #6
    Well, birds and insects would respond to 30-60 micro-Teslas, but humans wouldn't. Basically, I'm guessing that humans have some capacity to sense magnetic fields, but it's so weak in us and probably in other mammals that you would need a field a few orders of magnitude stronger than Earth's.

    It's easy to find general info on the web about magnetoreception, but hard to find anything very specific (e.g., a comprehensive list of organisms known to have it). Hadn't thought of the library though ....
  8. May 28, 2010 #7
    I believe that the March 2006 Scientific American has short article on space traveler shielding mentioning that someone would see flashes and have an acid taste when they moved their head while next to an accelerator magnet.

    Also see http://www.ru.nl/hfml/research/levitation/diamagnetic/
  9. May 28, 2010 #8


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    A chemist friend of mine claimed they could see colors by working with their head under the NMR magnet
  10. May 28, 2010 #9
    Magnetic field shouldn't have much effect (harmfully) on a human. At least if what you're doing is what I am reading you are doing.
  11. May 29, 2010 #10
    Wow! I would love to research that! Sounds like the sort of thing Jim1138 was talking about ... sadly, the Scientific American website won't let me view the whole article, so I couldn't read the part about magnetic field hallucinations. I did find some interesting stuff upon further googling, though. Jim1138, mgb_phys, do you think this is the sort of thing you're talking about?



    Thanks for bringing that to my attention!
  12. May 29, 2010 #11
    Yes, I think below about 10 Tesla you can't do much harm. But at some point a static magnetic field will do damage:

    http://solomon.as.utexas.edu/~duncan/magnetar.html [Broken]

    Last edited by a moderator: May 4, 2017
  13. May 30, 2010 #12
    huh, that's interesting. i had no idea a static field could do that.

    my one experience being in the same room as an NMRI machine left me feeling a little off-balance/weird. sure, static fields don't move ions and electrons. but that field is only static to the extent that you don't move within it. once you start rotating your body within the static field, it has the same effect as you sitting still while a multi-tesla field rotates across you. and as any engineer will tell you, a rotating magnetic field pushes current just fine. 'course, it's not actually that big a field just standing in the same room. you're just feeling the effects of the fringe field, which is much smaller than the field in the center of the machine.
    Last edited by a moderator: May 4, 2017
  14. May 30, 2010 #13
    I have seen a TV show about magnetic fields where a mouse was levitated inside a very strong magnet. The mouse show no signs of discomfort. So I suspect that your budget will be the limiting factor rather than the strength of the field humans can tolerate.
  15. May 30, 2010 #14
    You'll need to make sure you bounce all of your ideas off of whomever is assigned to deal with the projects. In the systems within which I do my work, to work with humans you need ethical approval - this can be time-consuming to obtain, especially when the work itself is original. (for instance, you may apply for ethical approval for some sort of brain imaging study, using commonly tested MRI. Here the ethics are about the data and care of patients moreso than whether or not the technique will show results. Testing without expectation is difficult to justify.)
  16. May 31, 2010 #15
    Yeah, I feel like this is a risky idea. :uhh: Not only is there the hassle of either getting approval to use humans or animals, but I really don't know if I'll see good results. I have a safer idea for an honors thesis that I also posted on the medical forum. I'd love to get some input on it, if some of you wouldn't mind reading it. Thanks!
  17. May 31, 2010 #16
    I always think of the library as being for humanities people .... :frown:
  18. May 31, 2010 #17
    I'm wondering if the distinction between static and oscillating magnetic fields doesn't become academic at some point regarding living systems. In terms of relative motion, the heart is beating, blood and lymph is flowing, and there are micro-currents everywhere. Obviously any motion in a "static" magnetic field creates electrical potentials.
    Last edited: May 31, 2010
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