Hello Karl, and welcome to ECN.
I have to confess that I'm not particularly well-read when it comes to the issues of EM fields on health, although naturally I've followed some of the stories over the controversy. Like many, I suppose I've seen the arguments from both sides and decided to take an agnostic view of the situation.
With regard to EMI to electronic equipment, this is something which has concerned me, as I frequently work with sensitive equipment involving very low signal levels. The problem of induced 50/60Hz hum is one which often takes quite a lot careful work to sort out.
The British ring circuit can certainly result in quite strong EM fields if one conductor is broken, but there can also be imbalance due to less-than-ideal connections. It takes only a little more resistance on one terminal to result in the split of current around the ring being different on the line and neutral.
