Microwave radiation is non ionising, which shouldn't really be as much a health risk as compared to some other radiation sources. That said, a typical microwave oven emits 800-1000W of microwave energy. Your router at 200mW for 2.4GHz, emits somewhere around 1/5000th of that. 5GHz is even less penetrating. You would probably prematurely burn out the chip on your router before it can emit any amount of energy significant enough to be an immediate health hazard.
That said, I am no health expert, but there are no reliable studies to associate cancer or other health problems with microwave energy thus far; otherwise microwave ovens and wireless routers would have been banned by now.
The other side of the coin is that blindly boosting TX to very high levels is not very useful, as a wireless connection is two way. Boosting your TX to a very high number can result in your device being able to see your router at very high signal strength at long ranges, but being unable to connect to it, as the TX from your device to your router is too weak.
In the past the firmware can be adjust the TX power of the wireless and when you place the router in your bedroom and you can easily get a headache when you get it to max.
