How does cosmic background radiation affect humans?
Probably, the CBR does not affect humans.
The reason is that it is just a radio hiss. Generally , radio waves do not harm tissue ( if you are not standing near the source, radio waves are non-ionic, that means that they do not change the DNA). There are many sources of radio waves-TV broadcast, cellular networks, they do not harm us. Alternative answer is that CBR had already existed when the life started on earth.The diversity of spicies evolved with the CBR around. So it does not harm and probably does not affect.