you routinely hold to your head a device that emits around 600 milliwatts RF.
If you are a keen yacht sailor you are worse off by far - VHF marine radios emit at 25,000 milliwatts.
Then there's that useful microwave in the kitchen - it emits at between 500 and 1000 Watts RF (that's watts, not milliwatts).
This is a highly copmplex matter, and I'm certainly not going to offer safety guidelines here, but in general terms, exposure to RF emissions in humans is measured by using a Specific Absorbtion Rate (SAR) per kilo of bodyweight, and a safe level is considered to be anything below 4 watts per kilo of bodyweight.
Above certain levels, RF absorbtion heats human tissue, and your eyes are especially vulnerable (as are the testes in males). You can rest assured however that the amount of RF emission coming from your wireless router is far below the safe limit, and well below the amount that you get from a mobile phone (and you hold that to your ear).
RF emission strength reduces with distance, and the further you are from the transmitter the less you will absorb. I doubt that your router is "burning my brain cells out 1 by 1 everyday" - you lose far more of them in other ways - each time you have a few drinks too many for instance. Not that I'm suggesting you do that.