Irv’s Sheet: Electromagnetic Fields, Hybrids and Health

Rumors and assertions about electromagnetic fields (EMF) from hybrid vehicles, and the harm they might do to humans, continue to surface.

Assumptions about possible EMF harm are based on the fact that hybrid vehicles are equipped with high-voltage electrical systems. Since an electromagnetic field’s intensity varies with voltage and current, hybrid vehicles are assumed to generate strong magnetic fields that may be harmful.

So I thought a quick primer on this topic might be helpful.

There are two different types of magnetic fields, and they are present in all automobiles, not just hybrids. Static magnetic fields are present around all permanent magnets found in audio speakers and electric motors such as those that drive power windows and seats.

Temporary magnetic fields, meanwhile, are created by current passing through a conductor or winding of wire. These fields are created to activate devices such as solenoids to open a vehicle’s trunk or to lock its doors.

Electromagnetic fields also are present in our homes and around power lines. The power in our homes and businesses is alternating current, or AC. This type of current emits an expanding/collapsing EMF around the wires that carry it 60 times each second. That’s why it’s known as 60-cycle current.

It is this type of EMF exposure that is the focus of health concerns. In fact, the World Health Organization (WHO) and the International Commission on Non Ionizing Radiation Protection (ICNIRP) study EMF at all frequencies, and its effect on human health. Due to the concerns of people living close to power stations and transmission lines, the ICNIRP established a maximum safe level for exposure to EMF.

Hybrid vehicles do have some high-voltage circuitry that pulses several times each second. However, these circuits are in the engine compartment and are shielded by metal cases and metal sleeves around the cabling. This virtually eliminates any electromagnetic emission beyond the cases or sleeves.

The battery packs and cabling typically located in the rear of hybrid vehicles store, supply and receive direct current (DC). While the intensity and direction of that current changes depending upon whether the batteries are charging or discharging, the frequency of change is very slow (a few seconds for each change) and the batteries and cabling are shielded.

We use various suppression remedies to reduce or inhibit electromagnetic fields in and around our vehicles. Based on established test criteria, our hybrids emit no more EMF strength than a conventional (non-hybrid) vehicle.

We’ve tested the electromagnetic field strength/frequency inside and outside our hybrid vehicles against the standard set by the ICNIRP. The measured EMF from a Prius is 1/300th of that guideline for the 50- to 60-cycle range.

Bottom line? As a result of shielding and careful design, we believe that the Electromagnetic Fields from our hybrid vehicles pose no health risks to drivers, passengers or bystanders.

- Irv Miller, Group Vice President, Corporate Communications

Comments

[BrianT in Etown]

looks like someone at G.M. has been hard at work in the rumor mill!

[BuyingAdvice]

I think it's a pretty brave decision for Toyota's PR department to even let this be mentioned at all. This is certainly the first I've heard of it. But I agree that it doesn't sound like a concern.

[Carmine Rende, Jr.]

Can I equip my 2004 Prius with the new solar panel roofs that will be coming out next year even if it means cutting off the old roof? Will I need major circuitry changes to do this and how much might it cost me?

[Amit]

What was the EMF guideline, against-which you performed your tests? Can you be more specific ( I.E. in terms of mG)?

Are the results of your EMF tests available on your website? Can you publish them, if not?

The fact that the batteries' I/O is DC doesn't really assure that there's no EMF generated in the car. Indeed, the prius has an AC/DC converter for converting DC->AC, fed to/from the engines, right? So, the leads under the passenger compartment actually convey AC, no?

[Jon Redd]

1/300th of the EMF guideline is still about 30 mG, which can be a concern for long term exposure, which you are not likely to receive in a hybrid car unless you are living in it with it continuely operating. (very unlikely if not impossible)
Also your comments about shielding from from metal cases applies to electric fields and not magnetic fields, which are the concern. These can be shielded by running the return line in pairs withthe primary power line, as in house wiring. Is this done in your hybrid cars? If it is, you should let us know about this additional shielding step you have taken.

[Jon redd]

My name is jon redd also. Thought it was cool.