Are you sure?
Maybe I get my boy a pair of Stax SR9 then, but did someone say tube amps are dangerous?
A pair of electrostatic headphone should emit less radiation than any headphones with magnets. By its principle of its operation, it merely a membrane attracted/repulse to a grid where it have a high potential difference, the current running through them will be very low. It shouldn't effect much of you, well, might move a staticy hair or two, but it shouldn't have any effect. It simply does not have a constant magnetic field that dynamic headphones have.
Not that dynamic headphones have any hazard or effects on the human body except providing music to your ears anyway.