The present study aimed to investigate the effects of chronic low-intensity microwave exposure (900, 1800 or 2450 MHz for 180 days) on cognitive function, heat shock protein 70 (HSP70), and DNA damage in the rat brain. The results showed declined cognitive function, elevated HSP70 level, and DNA damage in the brain of microwave-exposed animals. The results indicated that, chronic low-intensity microwave exposure in the frequency range of 900 to 2450 MHz may cause hazardous effects on the brain.
Have you ever felt more awake after using Wi-Fi or even struggled to sleep through the night? Reports of these phenomena have been frequent and even prompted a study in 2007 that evaluated low-frequency modulation from cell phones and its impact on sleep. Participants were exposed to the electromagnetic signals from real phones or no signal from fake phones. Those exposed to the electromagnetic radiation had a significantly more difficult time falling asleep and changes in brainwave patterns were observed. 
I turn my router off every night before bedtime. If it gets left on by a kid, I can tell immediately when I wake up in the morning because I do not feel nearly as rested. I am certain that the router for my level of sensitivity acts like a stimulant. When it is on and I am trying to go to sleep I feel as if I have had a couple cups of coffee. If it has been left on all night, when I wake up I feel just the same as if I had drank coffee close to bedtime and did not sleep soundly.
Cancer is the obvious start. An early concern with mobile technology was clusters of the disease around those living near phone masts. One study in Israel found a 4.5-fold increase in cancers of all kinds in the immediate vicinity of a mast (Int. J. Cancer Prev., 2004). In 2009, a Korean team of researchers carried out a pool analysis of the results of 23 studies, which involved almost 38,000 subjects.