When land is flat, such as with farm fields, then cell towers can be many miles away from each other, and it will not disrupt communication. When land has hills, then cell towers that are situated 3 miles away from each other will not disrupt communication (being 3 miles apart will be good enough for the signals to get through):
Because of risks of exposure to electromagnetic fields (EMFs), it would be good if laws are passed which require all new towers to be at least 3 miles away from any existing ones — and pre-existing towers closer than 3 miles from each other should be removed. Paying for the removal of towers too close would be an investment in human health.
Refusals to removing towers within 3 miles of each other could be met with lawsuits.