WiFi safety was back in the news thanks to a tweet from Green Party leader Elizabeth May:
It is very disturbing how quickly Wifi has moved into schools as it is children who are the most vulnerable.
Which set off a maelstrom of tweets from the extremes of the informed.
Some pointed to the World Health Organization advisory on mobile phones and had trouble discerning the differences. A key statement in the WHO advisory appeared to have escaped from people’s view:
The power (and hence the radiofrequency exposure to a user) falls off rapidly with increasing distance from the handset.Ā A person using a mobile phone 30ā40 cm away from their body ā for example when text messaging, accessing the Internet, or using a āhands freeā device ā will therefore have a much lower exposure to radiofrequency fields than someone holding the handset against their head.
Most of us do not walk around with a WiFi device strapped to our heads. Our laptop computers are usually more than the 30-40 cm distance away, at least when I am typing on mine. The Ontario Medical Officer of Health has said WiFi is OK, citing Health Canada standards. Princeton University – a school with a reasonable reputation – did a review of the literature to developĀ a position statement forĀ its staff and students to provide assurance that they were working in a safe environment.
What was the basis for whipping up anxiety over technology that is already built to meet national and international safety standards.
It is still July. I wasn’t ready for back-to-school special interest issues like this, despite the pre-release announcements from some of the phone companies. Next thing you know, the office supply stores will start those “most wonderful time of the year” jingles.
UPDATE: David Hillier provides the best link to sum up the WiFi issue.
Not to mention that laptops are typically transmitting far below the power levels of a mobile phone. Typical transmit power for a laptop is in the range of 70 mW. The WHO study above cites typical mobile phone transmit power of 0.1 – 2 W.
To make it worse, these concerns about WiFi in schools aren’t even regarding the use of laptops. The worry is that these children are exposed to some kind of dangerous RF soup just by being present in schools. WiFi routers are transmitting at ~0.1 W, but they are several metres, or tens or metres, away from the children.
Energy density decreases with the square of the distance, so if a router was only 5 metres away from a child, that would be over 15,000 times lower energy density than a mobile phone held 40 cm away, if they were transmitting at the same strength.