Health? If people only knew how much wireless traffic was being sent over the airwaves they would go dig a hole in the Grand Canyon and line it with lead.
As a society we are so dependent on radio signals to do our day to day jobs that adding 2.4 GHz Wi-Fi is not going to be an issue. Cell phones, police radio, satellite communications, HAM radio enthusiasts, CB radio, microwaves, cordless phones, cable networks, FM radio, just to name a few.
The US has a Frequency Allocation Chart that you may freely download and view, it contains all the various slices of bandwidth that are available, who is allowed to use them, and for what purposes.
The company I work for does not have any wireless network access points, mainly because we have no users using laptops and everyone is able to be hardwired. If anything we are more worried about the wireless being less secure than wired since to tap into our wired you would have to physically walk in, to get into wireless you only need to have a lot of time on your hands and a place to sit outside where our signal reaches.