The FCC sets the limits
In the United States, every radio transmitter, including cell sites, must keep human exposure to radio-frequency (RF) energy within limits set by the Federal Communications Commission, in its rules at 47 CFR 1.1310. The limits are expressed as maximum permissible exposure, a power density in milliwatts per square centimetre that depends on the frequency. They were based on recommendations from expert bodies and include a safety margin.
There are two tiers. The general population limit applies to the public, including anyone living near a tower. A higher occupational limit applies to trained workers, such as tower climbers, who are aware of the exposure and can control it.
The general population limits
| Frequency | General population limit |
|---|---|
| 300 to 1,500 MHz | Frequency in MHz divided by 1,500, in mW/cm². About 0.47 mW/cm² at 700 MHz |
| 1,500 MHz to 100 GHz | 1.0 mW/cm² |
Exposure near a tower is typically low
Cell antennas on towers point their energy toward the horizon, in a beam that is narrow vertically. Directly below and around the base of a tower, you are outside the main beam and far from the antennas. The FCC's guidance on cellular antenna sites states that ground-level exposure from typical cell towers is normally far below the limits.
The places where exposure can approach the limits are close to the front of the antennas themselves: on the tower, or on a rooftop right in front of a panel. That is why rooftop sites carry warning signs and barriers, and why workers follow procedures before climbing.
5G and the limits
5G equipment must meet the same FCC limits as earlier generations. Millimetre-wave 5G uses higher frequencies, where the limit is 1.0 mW/cm², and its signals are absorbed at the skin surface rather than deeper in the body. Small cells are closer to street level but operate at much lower power than macro towers.
Where to read more
If you have a concern about a specific site, the tower owner is responsible for compliance. Look the tower up to find the owner and its FCC registration number.
- The FCC's consumer guide on radio-frequency safety and its guidance on human exposure at cellular antenna sites.
- FCC OET Bulletin 65, the technical guide to evaluating compliance with the limits.
- The US Food and Drug Administration's pages on cell phones and radio-frequency energy.
This page summarises the regulatory limits. It is not medical advice.