Some approximate measurements of magnetic fields were made inside a moving 2010 Toyota Prius (hybrid electric/gas powered car) and a 2002 Ford Focus (gas-powered car). The magnetic fields (static and alternating), and the RF electromagnetic field, were checked. The measurements were made near the driver’s upper body and head. Only the driver’s exposure was checked, not the other seats, nor areas near the floor or dashboard. Sources of EMF in a car include the alternator, ignition system, wiring, fuel pump, and the Prius also includes an electric motor powered by rechargeable batteries. The air conditioner, fans, radio, and lights were off during the tests.
These magnetic fields are difficult to measure and characterize since the fields include alternating fields and changing levels of static fields, the earth's magnetic field is present, the car is in motion, turning, and bouncing, and the fields are different in different parts of the car. Most of the health effects studied by researchers have been from alternating 50 Hz or 60 Hz magnetic fields from power lines and in buildings. The static magnetic fields with changing levels that might be found in an electric car are more difficult to measure and have been studied less. These measurements were taken on a weekend afternoon with limited time available, so the results are approximate. We did not find very high levels of fields in the driver's seat.
Alternating magnetic field measurements: A Bell-4180 gaussmeter was used to measure alternating and time-varying magnetic fields, at frequencies from about 20 Hz to 2000 Hz. This gaussmeter is accurate for sinusoidally alternating fields at all these frequencies since it is not a frequency weighted meter. It does not measure the static magnetic field. Changes in a static magnetic field may be picked-up as a time-varying field by this gaussmeter. The Sypris Bell-4180 has a noise level around 0.3 to 0.4 mG so it cannot measure alternating fields less than that. Measurements were made while driving around a cemetery to provide an environment free of external EMF sources. The Ford Focus did not show any fields above 0.3 mG (the noise level of the meter), while the Honda Prius was slightly higher: up to around 0.5 mG. This slightly higher level measured near the driver of the Prius may be due to changing levels of static magnetic field. The highest fields were often seen while accelerating. Driving around corners had negligible additional effect on the reading. Measurements were also done along a road outside the cemetery, which showed much higher alternating field levels (up to 8.0 mG during our brief drive) for both cars, which is due to the overhead electrical power lines on the telephone poles by the side of the roads, especially along main roads.
Bluetooth RF: When the Bluetooth feature of the Prius was turned off the RF exposure near the driver was below 1 mW/sq.m. When Bluetooth was on the RF exposure was around 3 mW/sq.m. This is much lower than the 200 mW/sq.m. or higher exposure at the drivers head when holding a cell phone next to the driver's ear. These were the intermittent maximum RF exposures seen, not the average over time. These approximate RF measurements were made using an inexpensive RF meter with corrections from the Frequency Response Table. The 2002 Ford Focus did not have Bluetooth.
Static magnetic field (DC field or zero Hz frequency): We measured the static field using a Bell-5170 gaussmeter with its standard single-axis STH17-0404 probe. The accuracy of these static field measurements was around 500 mG because the probe has accuracy of about +/-0.1 G +/- 3 counts (0.1 G = 100 mG, and each count is also 0.1 G), and also the Earth’s static magnetic field is around 500 mG which was zeroed out before starting the measurements but it would then vary due to turning of the car and turning of the probe, and also due to the varying orientation of the car body. The measurements while driving in the Prius showed no consistent increase in the static magnetic field in the driver's seat above the 500 mG noise and background level. Therefore, the static fields were not very much elevated in the driver's seat. Changes in the static field (B-dot) would not be measured using this probe. A more sensitive low-field probe was not available, which might have revealed more information about the static field from to the DC electric power of the car, but the static field was not high enough to be measurable using this probe and setup. Since no significant increase of the static field could be measured in the driver's seat of the Prius during this rough experiment, it was not checked for the Ford Focus.
For more information:
http://www.nytimes.com/2008/04/27/automobiles/27EMF.html?_r=1
http://consumerist.com/5008376/hidden-hybrid-automobile-dangers-what-you-should-know-about-emfs
http://www.eiwellspring.org/EMFMeasurementsOfCarsAndTrucks.pdf
