My two cents:
I think Paul's suggestion to used metal conduit is good. It will significantly reduce the electromagnetic field.
Another solution is to use braided wires. (I mean that the wires are braided together, not that the core of each wire is braided.) I don't know if you can find that in the US, though. As you will still have to use conduit (plastic), the metal conduit is most likely a better choice.
