What do you mean by saying EMF causes danger to us ? Which frequency ? Any electromagnetic fields with frequency less than infrared can't do anything to us. Infrared and microwaves can heat up our body, if you are under a constant and intense radiation. For that you have to go inside microwave oven. Visible light is also dangerous if it's in an intense form (lasers). Electromagnetic radiations are present through out our universe. It's not only made by humans. You don't have to worry too much about this things. The most dangerous Electromagnetic radiations are coming from the sun. You can't do much about it other than applying sunscreen lotion.