The interval between relays largely depends on topographical, regulatory, and environmental conditions.
In any case, all our systems are designed to be absolutely safe for any organic life form.
Despite initial perception (mostly driven by the 5G frenzy I presume), if you do the research you'll realise that it is the most environmentally friendly solution out there. This is how EBDs can go green! No ELF, no people or animals immersed in RF or electrocuted, no carbon emission, no cutting through forests and rivers with huge pylons and no underwater cables disturbing marine life.
I hope this addressed your concerns?