It’s worth remembering that Wi-Fi occupies the same part of the spectrum as microwaves, which sounds terribly alarming. If it can boil water, surely it’s bad for us too? Well, no. Not at such low power. This is also the frequency of the cosmic background radiation, the echoes of the big bang that fill the sky. There is literally nowhere in the universe that does not have microwaves pinging around in it.
However, wireless routers are typically located significantly farther away from users' heads than a mobile phone the user is handling, resulting in far less exposure overall. The Health Protection Agency (HPA) says that if a person spends one year in a location with a Wi-Fi hotspot, they will receive the same dose of radio waves as if they had made a 20-minute call on a mobile phone.[7]
In 2011, the World Health Organization  classified radio frequency radiation of the type used by WiFi devices as a Group 2B possible carcinogen. A study conducted by the University of Vienna have found WiFi exposures to cause genotoxicity as they break single and double strand DNAs in our body. This indicates that there are effects that may potentially surface with our future generations.
Results Renal tissue malondialdehyde (MDA) and total oxidant (TOS) levels of pre-natal group were high and total antioxidant (TAS) and superoxide dismutase (SOD) levels were low. Spot urine NAG/creatinine ratio was significantly higher in pre- and post-natal groups (p < 0.001). Tubular injury was detected in most of the specimens in post-natal groups. Immunohistochemical analysis showed low-intensity staining with Bax in cortex, high-intensity staining with Bcl-2 in cortical and medullar areas of pre-natal group (p values, 0.000, 0.002, 0.000, respectively) when compared with sham group. Bcl2/Bax staining intensity ratios of medullar and cortical area was higher in pre-natal group than sham group (p = 0.018, p = 0.011).
In a separate study by the same Swedish team, they found more than seven times the risk among people using a cell phone more than 20 years and 6.5 times the risk for long-term users of cordless phones. As expected, most of the gliomas and acoustic neuromas were on the same side of the head, which was usually exposed to the phone. In the 2013 official report on the medical evidence for brain tumors, the International Agency for Research on Cancer concluded that radiation from cell phones is “possibly carcinogenic to humans”.