> Transmission lines are pretty harmless

Debatable. Some studies found this:

https://emfradar.com/articles/power-lines-childhood-leukemia

Then some other studies mostly invalidated that.

https://www.nature.com/articles/s41416-018-0097-7

There's a lot of people saying they aren't harmless but there's no credible evidence they aren't harmless. It's like flat earth, you know, there's no evidence the earth is flat.