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How strong would a magnetic field have to be to kill you?

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Re: How strong would a magnetic field have to be to kill you?

#21

Post by goodbyegti »

peter303 wrote: post #13

Something called Transcranial Magnetic Stimulation alters brain activity at about one Tesla (10,000x earth's field). TMS has been shown to induce euphoria, amnesia, and relieve depression. Unclear what stronger magnetic fields could do. A ten Tesla magnet can levitate a small animal.

I work in this sector, and what you say is correct, however it is important to note that in TMS the fields are pulsed over millisecond time intervals. In doing so they can induce an electric field which can cause neurons to fire. The time varience is crucial. A 3T static field from the magnet of an MR scanner is far less dangerous than a 1T field pulsed in the vicinity of your brain. That is providing that there aren't any ferromagnetic objects close to the MR scanner!

Re: How strong would a magnetic field have to be to kill you?

#22

Post by Irene »

Relatively weak MFs could kill as an indirect result of the injury: http://mentalfloss.com/article/18405/mri-magnet-madness http://boards.straightdope.com/sdmb/showthread.php?t=544233

The effect depends on field signal characteristics (frequency, amplitude, wave shape), duration of exposure, genetics and metabolism. Some bacteria can be negatively affected even by 10 mT. In clinical trials people were "safely" exposed to up to 3 T.

Re: How strong would a magnetic field have to be to kill you?

#23

Post by Sharlin »

msandford wrote: post #4
mrfusion wrote: post #2

Wouldn't iron in blood be affected well before this point though?

Not necessarily. Iron oxide is somewhat ferromagnetic but iron chloride is paramagnetic. So just having some iron atoms in something isn't enough to make it ferromagnetic. http://www.thenakedscientists.com/HTML/questions/question/28...

Indeed, even stainless steel isn't necessarily ferromagnetic, even though it's mostly iron.

Re: How strong would a magnetic field have to be to kill you?

#24

Post by ursidae »

TheLoneWolfling wrote: post #3

I think that you'd end up with neurological effects before the electrons were ripped out of atoms. I mean, our nervous system is effectively controlled ionic exchange.

For a practical example of this, see 'Transcranial Magnetic Stimulation':

http://en.wikipedia.org/wiki/Transcranial_magnetic_stimulati...

Re: How strong would a magnetic field have to be to kill you?

#25

Post by ursidae »

goodbyegti wrote: post #21
peter303 wrote: post #13

Something called Transcranial Magnetic Stimulation alters brain activity at about one Tesla (10,000x earth's field). TMS has been shown to induce euphoria, amnesia, and relieve depression. Unclear what stronger magnetic fields could do. A ten Tesla magnet can levitate a small animal.

I work in this sector, and what you say is correct, however it is important to note that in TMS the fields are pulsed over millisecond time intervals. In doing so they can induce an electric field which can cause neurons to fire. The time varience is crucial. A 3T static field from the magnet of an MR scanner is far less dangerous than a 1T field pulsed in the vicinity of your brain. That is providing that there aren…

Radiologist here. We regularly image patients in 3T MRI scanners. As long as they don't have certain metal surgical implants, a pacemaker, or metallic foreign bodies, there is no problem.

Some institutions have research magnets up to 7T: http://www.healthcare.philips.com/main/products/mri/research...

Re: How strong would a magnetic field have to be to kill you?

#26

Post by makomk »

VLM wrote: post #10
jorjordandan wrote: post #9

I think you would be killed by the diamagnetic properties of water first... If you can affect water with a small magnet like this: https://www.youtube.com/watch?v=2FvWtEdY4sE Then a magnetic field of sufficient power would probably kill you long before the effects described in the article. I'm amazed that someone other than me has thought about this!

Blood electrocution would get you first. Moving conductor in a magnetic field generates a current, and you'd just need a current big enough to confuse the cardiac nerves. Given that existing MRI research magnets can give weird nervous system feelings when patients wiggle, just an order of magnitude or two more and you'd get knocked out by your own circulating blood.

Don't most of the problems with nerve stimulation in existing MRI systems come from the gradient coils rapidly modulating the magnetic field, rather than people moving around?

Re: How strong would a magnetic field have to be to kill you?

#27

Post by xaa »

ursidae wrote: post #25
goodbyegti wrote: post #21

Earlier quoted context omitted.

I work in this sector, and what you say is correct, however it is important to note that in TMS the fields are pulsed over millisecond time intervals. In doing so they can induce an electric field which can cause neurons to fire. The time varience is crucial. A 3T static field from the magnet of an MR scanner is far less dangerous than a 1T field pulsed in the vicinity of your brain. That is providing that there aren…

Radiologist here. We regularly image patients in 3T MRI scanners. As long as they don't have certain metal surgical implants, a pacemaker, or metallic foreign bodies, there is no problem. Some institutions have research magnets up to 7T: http://www.healthcare.philips.com/main/products/mri/research...

My research institute has a 11.7T (for small animals).

Although I must say, using MRI, even such a powerful one, for research is not as useful or cool as you'd expect since it takes so long to do one scan.

Re: How strong would a magnetic field have to be to kill you?

#28

Post by avian »

ursidae wrote: post #24
TheLoneWolfling wrote: post #3

I think that you'd end up with neurological effects before the electrons were ripped out of atoms. I mean, our nervous system is effectively controlled ionic exchange.

For a practical example of this, see 'Transcranial Magnetic Stimulation': http://en.wikipedia.org/wiki/Transcranial_magnetic_stimulati...

TMS uses magnetic fields that change with time while the linked article talks about the effect of static magnetic fields.

Re: How strong would a magnetic field have to be to kill you?

#29

Post by sandworm »

Has anyone looked at the effects not on particles, but on changes to reactivity in the presence of magnetic fields? You don't need to rip apart molecules to kill us. Make certain reactions a little more or less likely to occur and we stop functioning.

I have seen some discussion of how heavy water could be lethal if it were to replace all of a body's water based on its very slight differences in reactivity.

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