billy wrote:

What material can be used for shield against potentially dangerous
levels of radio waves. Lets say outside my bedroom is a radio
communication device. What material could stop the waves from
entering. Cement? Lead? How thick?

simple copper screen (like screen door stuff) properly bonded and grounded
would do the trick nicely.

cement is partially effective (you need truckloads to do any good though )
and don't even talk about lead (the EPA would have you for lunch).

lets see, copper screen (.05 inch thick) completely around the room (plus
ceiling) properly grounded = 99% effective

cement: 1 foot thick, 10%
Lead? not sure