Re: Power Lines and Magnetic Fields

[John Moulder <jmoulder@post.its.mcw.edu>]

> I attended a very interesting Central Rocky Mt. HPS meeting last 
> year which discussed cancer risk and electrical wiring..... 

> The speaker said E fields had been ruled out but didn't give detail.

Simple reason: The E-field does not penetrate buildings, so if powerlines had 
an effect it would have to be due to the H-field.
  
> Gentleman also pointed out that it was like trying to show a 
> correlation between lung cancer and smoking if the baseline were a 
> pack and a half a day instead of nonsmokers.  That is we are all 
> exposed to the magnetic and electric fields from power lines to 
> some extent.

I've heard this before, but its not really a good analogy:
1)  You can detect a statistically significant difference in risk between 
various levels of smokers.
2)  The range of ambient exposures is actually quite large.  If you look at 
the 24-hr residential measurements of Kaune et al (Bioelectromag 8:315-335. 
987), the lower quartile would be 0.02 microT and below, and the upper 
quartile would be 0.2 microT and above. The distribution of occupational 
exposures is a bit tighter (Floderus et al, Cancer Causes Control 4:465-476, 
1993) with the lower quartile being at 0.15 microT and below, and the upper 
10% being at 0.41 microT and above.
3)  Most of the lab studies have been done with quite strict control of the 
exposures received by the "unexposed" group, with some cellular studies even 
going to the extreme of using mu metal shielding for the controls.  And these 
studies have shown absolutely no evidence for genotoxicity at any level of 
exposure, and no evidence of bioeffects at all for fields below about 20 
microT.

BTW: There is a voluminous and extensively referenced FAQ sheet on this topic 
in sci.med.physics (a usenet newsgroup).  Its also available by FTP and on the 
Web (see sites after my sig).  Next time I post it, I will place a pointer 
file here.  If anyone want's a copy and cannot get it by FTP or Web, e-mail a 
request to me -- but identify yourself as a member of this list, or I'll 
ignore the request (: