I had a girl friend who lived next door to a PG&E substation and she was concerned about EMF's. I think she had a cat that had feline leukemia. I bought a relatively cheap device that was effective in determine field strength. We also had PG&E come out with one of their expensive hand held meters to survey fields in her apartment. I still have that device and use it once in a while. I've surveyed my house, determined what devices put out what kind of fields whenever I've had a concern.
In general anything below 2 Milli Gauss is fairly safe. If you have sustained levels higher than that it becomes a concern. It affects children more than adults.
A point source of EMF's falls off as the inverse of the square of the distance from the source. However, a line source (i.e. a power line) falls off as the inverse of the distance, not the square, so living near high power lines is much more of a concern than near a point source.