RF/MW radiation hazards and safety practices

RF/microwave radiation is non-ionising (photon energy far below that needed to break chemical bonds), but it is absorbed by the body and converted to heat. Hazards arise when the power density or SAR is above safe limits.

RF/MW radiation hazards

Thermal effects (main, well-established):

• Water molecules in tissue rotate with the field; the energy becomes heat (dielectric heating).
• Organs with poor blood flow cannot remove heat: eyes (cataract) and testes (temporary sterility) are most sensitive.
• Whole-body heating raises body temperature, causing heat stress, fatigue and burns at high levels.
• Penetration depth falls with frequency: at 2.45 GHz a few cm, above 10 GHz mostly skin heating.
• Human body resonance (about 70–100 MHz for an adult) gives the highest whole-body absorption.

Non-thermal effects (studied, less certain): headaches, sleep disturbance, changes in nervous and cardiovascular response, and possible genetic effects. IARC (WHO) classes RF fields as "possibly carcinogenic to humans" (Group 2B).

Other hazards: sparks and ignition of fuel (HERF), triggering of electro-explosive devices (HERO), and interference with pacemakers and medical implants.

The absorbed power is measured as SAR = σ|E|²/ρ (W/kg).

Safety practices

1. Follow exposure limits: ICNIRP / IEEE C95.1: whole-body average SAR 0.08 W/kg (public) and 0.4 W/kg (occupational); localised (head/trunk) 2 W/kg and 10 W/kg over 10 g.
2. Distance: power density falls as 1/r², so keep away from antennas, especially in the main beam; mark exclusion zones around BTS and radar antennas.
3. Time: limit exposure time (limits are averaged over 6–30 minutes).
4. Shielding: metal enclosures, mesh, RF-absorbing material; microwave ovens use door mesh and chokes.
5. Switch off / lock-out transmitters before working on antennas or waveguides; never look into an open waveguide or horn.
6. Monitoring: survey sites with calibrated field meters; workers can wear personal RF monitors.
7. Signs and training: warning signs, fencing, and training of technicians.
8. Equipment maintenance: check oven door seals and waveguide flanges for leakage.