The only way one can access the danger of a new source of radiation is to compare it with existing ones (WiFi concerns still up in the air, Letters, 24 May).

The effective radiated power of a typical WiFi network adaptor is less than a tenth of that given out by a mobile phone, but more importantly its distance from the user’s brain is much greater.

A  mobile phone is typically used one inch from the user’s brain, a WiFi adapter is 50 inches. Radiation weakens in proportion to the square of the distance, so at 50 inches is 2,500 times  weaker than it is at one inch.

Allowing for the lower power, this makes the radiation received from a computer’s WiFi adaptor about 25,000 times  less than that from a mobile phone.

If WiFi is dangerous, then mobile phone users should be dropping dead in their millions, yet they do not seem to be. If we really want to get paranoid about radiation, how about closing down the ITV and BBC transmitters? They radiate millions of times more power than a WiFi adapter.

Harry Leeming