"The strength of RF fields is greatest at its source, and diminishes quickly with distance. Access near base station antennas is restricted where RF signals may exceed international exposure limits." http://www.who.int/mediacentre/factsheets/fs304/en/index.html
WiFi transmission is NOT "much lower". Emission by a WiFi router from a far distance may be lower, but WiFi (unlike AM/FM radio) is used for 2-way communication. The router is only one transmitter on one side - the iPad/laptop is the other microwave transmitter on the other side, the side where the users/children are. In a 21st Century Learning 1:1 iPad/laptop classroom, the antenna in every laptop and iPad transmits microwave directly at the user. There is no distance from these devices. The iPad/laptops are the "sources" of WiFi radiation.
Many other cellphones have lower SAR than iPhone:
* When measurement was taken on another occasion in an urban business district where a lot of celltowers exist, the general ambient level of RF was higher, but the radiation from the iPhone lowered to 0.2-1.7 µW/cm2 during talking transmission (because it could access the celltower more easily/readily). When the iPad was tested at the same spot (about 25 feet from a wireless router), however, the radiation remained high, peaking every couple seconds to 55-65 µW/cm2, as seen in the follow video).
SAR is measured on a time-averaged basis. Unlike cellphone on a voice transmission which is continous, WiFi microwave signals spike then drop to zero repeatedly and rapidly. The peak level radiation of the WiFi-iPad is actually many times higher than the talking-iPhone, to result in a comparable time-averaged SAR value.
See this video of an iPad on WiFi:
Reason: According to the Canadian Wireless Telecommunications Association, "an average smartphone uses 35 times the bandwidth of a regular cellphone, while a tablet uses up to 121 times the bandwidth." http://goo.gl/QHYpS
It's practically a 12-lane full capacity data highway traffic.
The Health Canada advice on WiFi - along with what's printed in the dated WHO fact sheet - are both based on the assumption that WiFi signals are received from a "distance". They only provide assurance about low ambient/background radiation levels from a "distant" source. They do not apply to the 21st Century Learning scenario where each student is expected to use a tablet/laptop (RF-microwave transmitters) with high level of radiation sent out right against their chests, abdomen, their laps and their hands, for hours a day.
Offering a child an iPad for hours a day (with WiFi on, regardless whether internet is accessed or not) is similar to giving a child an actively-transmitting cellphone (as during a phone call) to handle for hours a day.
Pushing the use of iPads for long duration = pushing for similar health consequences as seen from heavy cellphone use, except now it's on younger and more vulnerable brains and bodies.
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