NY times article on "health risks" from driving hybrids

[texnet]

Google leukemia and emf and the first item says:
The statement by NIEHS (and its director, Ken Olden) that the EMF/leukemia association is "weak," because there is no confirming biological evidence, ..

Sounds like someone trying to get media attention.

The Times article is a clear case of Prius envy to me... Just have to laugh!

[donee]

Hi Chogan,

As the field of 14 mGauss is next to the battery, one can infer that is static, or slowly varying level. As batteries have a large damping effect on the change in current. The only induction effect would be when the current reversed directions, such as switiching from electric drive to electric braking.

Movement through a static field is the same as a varying field, with respect to the current induced. Its the vector dB/dt magnitude that induces current. So, turning in a static field, like a generator armature does, induces current.

When one makes a turn more than 90 degrees out-of-doors the effect of the earth's magnetic field is probably larger. So the thing is, do people turn on their heels as fast as a Prius changes from electric drive to electric braking. I would guess the change is similar, or the Prius has a slightly greater vector rate of change, but static field is much less. Even if the Prius had a quicker current rate of change than a person turning a corner, it would need to be 35.7 times quicker (500 mG/ 14 mG) for the effect to match the effect of walking around a sharp corner in a magnetically unshielded room on the surface of the earth. Say people turn a corner in 1/2 a second. Then the Prius would need to change from electric power to brakes in 14 msec. Which seems unreasonably fast for motors and drive in a Prius. What is more typical in driving is one eases off the accellerator peddle, slowly droping current to 0, then one goes into glide, and evenuatlly brings the brake pedal up, all over a period of about 10 seconds, not .014 seconds.

The issues with EMF's in the workplace, is that these are continuously varying fields driven by AC line currents. Such as large transformerers without shielding (aluminum or plastic enclosures), or workers right next to a 4 foot diameter printing press motor with aluminum end caps (for example). Its not the same thing.

[chogan2]

Originally Posted by donee

Hi Chogan,

As the field of 14 mGauss is next to the battery, one can infer that is static, or slowly varying level. As batteries have a large damping effect on the change in current. The only induction effect would be when the current reversed directions, such as switiching from electric drive to electric braking.

Movement through a static field is the same as a varying field, with respect to the current induced. Its the vector dB/dt magnitude that induces current. So, turning in a static field, like a generator armature does, induces current.

When one makes a turn more than 90 degrees out-of-doors the effect of the earth's magnetic field is probably larger. So the thing is, do people turn on their heels as fast as a Prius changes from electric drive to electric braking. I would guess the change is similar, or the Prius has a slightly greater vector rate of change, but static field is much less. Even if the Prius had a quicker current rate of change than a person turning a corner, it would need to be 35.7 times quicker (500 mG/ 14 mG) for the effect to match the effect of walking around a sharp corner in a magnetically unshielded room on the surface of the earth. Say people turn a corner in 1/2 a second. Then the Prius would need to change from electric power to brakes in 14 msec. Which seems unreasonably fast for motors and drive in a Prius. What is more typical in driving is one eases off the accellerator peddle, slowly droping current to 0, then one goes into glide, and evenuatlly brings the brake pedal up, all over a period of about 10 seconds, not .014 seconds.

The issues with EMF's in the workplace, is that these are continuously varying fields driven by AC line currents. Such as large transformerers without shielding (aluminum or plastic enclosures), or workers right next to a 4 foot diameter printing press motor with aluminum end caps (for example). Its not the same thing.

Fair enough and true enough. I was mixing apples and oranges.

But.

But my only reservation -- and the reason I was willing to look further -- is that it's an assumption that the induced current is the only effect.

For sure, induced electrical currents are known to affect certain types of cell growth. The key example is the bone growth stimulator, a device used to help heal broken bones. Here's a description of one of the larger manufacturers, Biomet:

Biomet Europe: EBI® Bone Growth Stimulators

The odd thing is (here's the "but" part), researchers also show effects with static or slowly changing magnetic field alone, in vitro. But the fields are huge (cite below, 0.4Tesla = 4000 gauss). So, really strong static magnetic fields will also mess with bone cells in various ways. But the strength is, what, 5 orders of magnitude stronger than what you could possibly expect from sitting in a Prius.

Effects of static magnetic fields on bone formatio...[J Dent Res. 2003] - PubMed Result
Static magnetic fields promote osteoblast-like cel...[Ann Biomed Eng. 2007] - PubMed Result

I should have quit while I was ahead. I mixed standard based on 60 hz fields with the (largely) static field in the Priuis. Not smart. My only excuse is that it's not clear that the induced current is the only possible biological effect. But the effect of static field has only been shown for very large fields.

[Godiva]

And don't drive your Prius when it's raining or you might get electrocuted.

[tasker109]

i wonder who funded the research? that reminds me of a joke i once heard....


a man was interviewing accountants to hire to work for him. he had the first interviewee come in and asked him what 1+1 was. the interviewee said well 2 of course. the man said, thank you very much. we will be in touch. the second interviewee came in and the man said, what is 1+1? the interviewee looked at him funny and said, it's 2. the man said thank you very much, i will let you know. the third interviewee came in and the man said, what is 1+1? the interviewee looked around the room, looked over both shoulders, got up and looked up and down the hall outside the office, went over to the window and pulled the blinds. came back and sat down and said.......what do you want it to be? the man said.........YOU'RE HIRED!

[neon tetra]

I don't think it's necessarily an anti-Prius thing. People have been talking about this for a while on other vehicles, and especially airplanes.

If it's a concern, then it should be examined. If it turns out to be nothing, then even better.
But I do see a bit of a trend on this board to be overly apologetic about car & to almost deny that some of the problems exist.

[burritos]

Originally Posted by neon tetra

I don't think it's necessarily an anti-Prius thing. People have been talking about this for a while on other vehicles, and especially airplanes.

If it's a concern, then it should be examined. If it turns out to be nothing, then even better.
But I do see a bit of a trend on this board to be overly apologetic about car & to almost deny that some of the problems exist.

Then shouldn't studies be done to see if regular car batteries have any risk?

[qbee42]

Originally Posted by chogan2

<snip> But the fields are huge (cite below, 0.4Tesla = 4000 gauss). So, really strong static magnetic fields will also mess with bone cells in various ways. But the strength is, what, 5 orders of magnitude stronger than what you could possibly expect from sitting in a Prius.

I'm probably in trouble then, as I've spent a lot of time in a 1.5 Tesla field.

Tom

[chogan2]

Originally Posted by qbee42

I'm probably in trouble then, as I've spent a lot of time in a 1.5 Tesla field.

Tom

Well, these were cells in petri dishes, so to speak. And it didn't cause them to mutate, just caused them to change. No effect was demonstrated in people. Scanning the literature at the National Library of Medicine, as far as I can tell there's complete agreement that there's no hazard to patients from the magnetic field other than the obvious ones.

But there's always something. Googling it, it looks like the EU published a regulation limiting chronic exposure for MRI technicians.

MTB Europe - European Directive on radiation exposure will ban MRI scans

Despite a lack of evidence:

Impact of electromagnetic field exposure limits in...[Acad Radiol. 2005] - PubMed Result

And the NZ standard is that technicians have to stay far enough away to keep the field down to 0.2T.

http://www.nrl.moh.govt.nz/publicati...guidelines.pdf

All of these exposure limits appear precautionary (ie, there's no evidence of harm from chronic exposure), all are hugely higher than what was measured in a Prius. I looked for any epidemiologic study of MRI technicians and found nothing.

Your point's well taken. If there's no hint of harm from chronic exposure to MRI-strength fields, it's foolish to worry about the magnetic field in the back seat of a Prius.

[qbee42]

That's where my exposure came from. I managed the design engineering group for a large MRI company.

Tom