Another thing, a WiFi router is not continuously sending data, when devices don’t communicate to the internet. In an idle situation, a WiFi router just sends beacon signal, like “Hello I’m a WiFi router” every x miliseconds and your smartphone just listen to it, like a radio. The same is for GSM/3G/4G. Your mobile is not communicating to the GSM antenna continuously, otherwise it would drain your battery in minutes and your mobile gets very hot. Further more, the government forced the mobile companies to lower the transmit power, that’s why you see more GSM antennas (actually called basestations) in places like cities for better coverage.
The highest typical daily exposure, according to a study of 2009, came from cellphone base stations, cellphones and DECT cordless phones, with the highest exposure locations in trains, airports and buses.[17] The typical background power of electromagnetic fields in the home can vary from zero to 5 milliwatts per meter squared.[citation needed] Long-term effects of these electromagnetic fields on human and animal health are still unknown.

The device comes in a variety of forms ranging from the $39 Aries Shield ("a silicon based micro processor that ... decomposes oscillations of electromagnetic fields") to the $249 Aires Defender Utility (which "has two next generation 9 core silicon based micro processor (sic) that provide universal protection from electromagnetic smog of the broadband frequencies").

It should be noted that the given values of SAR were normalized to 1 W peak antenna power output, while typically a WLAN antenna radiates about 10 mW; therefore, for a real world operating system, maximum SAR of 0.37 × 10−3 and 0.18 × 10−3 (W/kg) is expected for 2 and 1 active antennas, respectively, which are 104 times lower than the European safety limit (2 W/kg) [IEEE Standard for Safety Levels with Respect to Humans, 2005].
Remarkably, cell phones had been allowed onto the US consumer market a decade earlier without any government safety testing. Now, some customers and industry workers were being diagnosed with cancer. In January 1993, David Reynard sued the NEC America Company, claiming that his wife’s NEC phone caused her lethal brain tumor. After Reynard appeared on national TV, the story went viral. A congressional subcommittee announced an investigation; investors began dumping their cell-phone stocks; and Wheeler and the CTIA swung into action.2
Cell phone storage in front pockets has been linked to poor fertility and higher chances of miscarriage and childhood cancer. [18] According to the Cleveland Clinic Center for Reproductive Medicine, semen quality "tended to decline as daily cell phone use increased." [19] According to a May-June 2012 meta-study in the Journal of Andrology, "men using mobile phones have decreased sperm concentration" in addition to "decreased viability" of their sperm. [64]
We requested semen for analyses from the male patients coming to our infertility division and also asked them to fill out an anonymous questionnaire. We queried their mobile phone and wireless internet usage frequencies in order to determine their radiofrequency-electromagnetic radiation exposure. A total of 1082 patients filled the questionnaire but 51 of them were excluded from the study because of azoospermia. 
Joel Moskowitz (@berkeleyprc) of the University of California, Berkeley School of Public Health, US, says: “This is the largest technological experiment in the history of our species, with potential health risks we still know next to nothing about.” This view is shared by Denis Henshaw, professor of human radiation effects at Bristol University, UK, who said: “Vast numbers of people are using cell phones and this could be a time bomb of health problems.”