Re: Magnetic fields in cars

[John Moulder <jmoulder@MCW.EDU>]

>The "information" provided tells something like: "To sit in a car is just as

>dangerous as standing under a power line. Inside the cars there are extreme

>magnetic field strengths - up to eighty times higher than normal. Much lower

>fields have been shown to cause childhood leukemias and miscarriages."



I have a bit more information.



The original story was from Vi  Bilägare.



The cars with the highest time-varying ELF  fields were Volvos.  The 

measured fields were stated to be 12-18 microT measured at the 

drivers left foot.  This drops to 0.9 microT at chest height and 0.6 

microT at head height.  The European public exposure standard is 

about 100 microT (some uncertainty because the frequency of the field 

in the car is unclear and the standard is frequency dependent).



In comparison the field under a  high-voltage power line is 3-10 microT.



The field in the Volvo appears to be created mainly by the wire(s) 

carrying the current from the alternator (in the engine compartment) 

to the battery (in the trunk).



What is the field?  Here I am pushing my knowledge of automobile 

engineering.  I am guessing that the cable carries rectified DC (the 

rectifier is at the alternator, not at the battery).  So the field is 

time-varying, but it is not AC.  Presumably the frequency is a 

function of the engine speed, since the engine is directly coupled to 

the alternator.



I have no information about how the measurements were done.  This may 

be an issue since a gauss meter designed to measure sinusoidal 

power-freqency fields may or may not be accurate when faced with 

other wave-forms and other frequencies.



>There is a reference to a newly published Californian study where it has

>been found that pregnant women had miscarriages after exposure to magnetic

>field environments above 1.6 microtesla. (I am interested in this reference

>if any Radsafer can help)



This is almost certainly reference to:



Lee, G. M.; Neutra, R. R.; Hristova, L.; Yost, M., and Hiatt, R. A. A 

nested case-control study of residential and personal magnetic field 

measures and miscarriages. Epidemiology. 2002; 13:21-31.



Li, D. K.; Odouli, R.; Wi, S.; Janevic, T.; Golditch, I.; Bracken, T. 

D.; Senior, R.; Rankin, R., and Iriye, R. A population-based 

prospective cohort study of personal exposure to magnetic fields 

during pregnancy and the risk of miscarriage. Epidemiology. 2002; 

13:9-20.



-- 



John Moulder (jmoulder@mcw.edu)

Electromagnetic Fields and Human Health

http://www.mcw.edu/gcrc/cop.html

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