I have a question regarding this Netgear 3800 Wireless Router:
Is the level of radiation emitted by the wireless dangerous ? It is advertised as dual-band but no mention about SAR.
Nope, nothing to worry about. Cell phones use 1000 milliWatts (mW) or more to reach a cell tower that may be kilometers away, while Wi-Fi gear typically uses 100mW or less to reach gear less than 50 meters away. Plus you don't hold the AP to your head, it sits 1-50 meters away from you.
Note that Wi-Fi is just radio waves in the 2.4GHz and 5GHz bands, which are far below the ionizing range. On the electromagnetic spectrum, radio waves make up the lower frequencies, visible light is in the middle, and X-rays and gamma rays make up the extremely high frequencies above ultraviolet light. Electromagnetic waves at or below the frequency of visible light are considered non-ionizing radiation because they don't have the ability break apart molecules into ions. Only electromagnetic waves higher in frequency than visible light (such as X-rays and gamma rays) have the ability to break ions off of molecules. The only known health effects from EM waves at or below visible light is the heating they may cause at sufficient power levels, like the way a 100W incandescent lightbulb gets hot, or the way you feel so-called "radiant heat" in front of a fire, which is actually just you being bathed by infrared light. Note that for your microwave oven to reheat your dinner, it has to bombard it with typically a kiloWatt (1,000,000 mW) or more, so 10,000x the power of a typical Wi-Fi AP.
I feel it's not exactly fair to call Wi-Fi's radio waves "radiation", because most people use that term to refer to nuclear radiation, like they way the decay of unstable radioactive isotopes releases alpha and beta particles and gamma rays. There is no nuclear radiation involved in Wi-Fi. It's just radio waves. If you don't think of the much higher frequency (400-790 TeraHertz) and intensity (100 W) electromagnetic waves radiating from your lightbulb to be irradiating you, then you shouldn't think of your radio devices as irradiating you either.