Regarding Electric and Magnetic Fields (EMF) Radiation from Power Lines:
There are plenty of reports and studies on this subject; however, I'm not sure a FINAL conclusion to this question has been reached. I have run into topic on more than one occasion. For an opinion I turned to a friend who is an electrical engineer who wrote the following:
"In general, the power of the EM field rolls off with the square of the distance from the source. I think that I read somewhere that 300 feet is the region of concern. However, 60 Hz is very low frequency, and I really donâ€™t think there is much merit to the health concern. Also, if you are within a foot of a power cord in your home or office, or even a wall with power running in it, youâ€™ll be exposed to the same field strength (you have to be close though)."
You can also read more about this topic here: http://www.epa.gov/radtown/power-lines.html
The truth is that some people will not care about the electrical towers and some will. I would say given a choice, Buyers would choose not to live by electrical towers (or any other non-standard condition) for aesthetic and/or health concerns (whether justified or not). These sensitivities will ebb-and-flow depending on supply/market conditions and how long the Buyer plans to occupy the property.