Keep them away from your mouse, keyboard, System Unit, and printer. 2 Repetitive Stress Injury happens when you do the same thing over and over. Chair Height must be right so your forearms are level with the floor. Lighting in the room must be right so your eyes aren't straining to see things. Clean the screen with windex and a paper towel.
Monitors are safe to be near.
There's no danger of radiation like people once thought. Mouse Height can be important too, especially if you click a lot.