All signal boosters are regulated by the FCC to ensure that there is no potential for harm to any living thing by an improperly designed, manufactured, or installed system.
A cell phone signal booster is designed to be as safe as possible for anyone who may come into contact with it. All signal boosters are heavily regulated by the FCC, both to prevent impact to the carrier networks and to ensure that there is no potential for harm to any living thing by an improperly designed, manufactured, or installed system.
The maximum amount of power that a cell phone signal booster can produce is less than or equal to what you would find from any WiFi access point, or what you would experience if you were close to a cell tower in an urban area, so there should not be any noticeable difference to anyone who is already able to be in strong cellular signal areas without impact.
As such, every precaution has been taken to ensure that cell phone signal boosters are safe for everyone, including people who are electromagnetically sensitive