Does wifi have any effect on one's health?
Compared to holding a mobile phone against your head, the exposure levels are very low.

So, even if non-ionizing radiation is found to be a health concern in the future (current studies show no reason for concern), wifi isn't going to be the primary source of exposure for most people.

If you are concerned, locate your router somewhere other than directly next to a desk.

Some router configuration software also allows you to set the transmit power level, so you can lower the power levels to a place where you still get acceptable bandwidth in the areas of the house where you use wifi.