EU Recommendation 1999/519/EC

EU Recommendation 1999/519/EC contains the same non-ionising radiation exposure limits, as 1998 ICNIRP guidelines. Limits are based on 6 minutes exposure.

1998 ICNIRP, P.14 reviews ‘Mircowave hearing’ & Auditory effects

People with normal hearing can perceive pulse-modulated fields with frequencies between about 200 MHz and 6.5 GHz. The auditory sensation has been variously described as a buzzing, clicking, or popping sound, depending on the modulation characteristics of the field. The microwave hearing effects have been attributed to a thermoelastic interaction in the auditory cortex of the brain, with a threshold for perception of about 100–400 mJ for pulses of duration less than 30 ms at 2.45 GHz (corresponding to an SA of 4–16 mJ kg-1). Repeated or prolonged exposure to microwave auditory effects may be stressful and potentially harmful.

To protect children and the public from harmful auditory effects, specific energy absorption (SA) limits were introduced. The SA limits are 2mJ/kg-1 for the general public, and 10mJ/kg-1 for people in the workplace. Based on ICNIRPs 2.45Ghz example, it is estimated a 2.45Ghz signal of circa 50mW/m2 exposure will cause an SA of 2mJ/kg-1.

Important tech note: A 50mW/m2 2.45Ghz signal in 1998 contained less energy than 50mW/m2 signal in 2021.  Wi-Fi developments have increased channel bandwidth, added more antenna (MIMO) etc. This combination of developments means there are greater levels of energy in today’s 2.45Ghz 50mW/m2 signals than those in 1998.