Regarding compact fluorescent bulbs

"When a concern is raised, error on the side of caution."

Someone asked my wife today if compact fluorescent bulbs (CFL's) are dangerous and do they need to be enclosed in a fixture when used.

I did a bit or research and confirmed what I already knew.  The concern is that each CFL contains a small amount, around 5 milligrams,  of highly toxic mercury aka quicksilver.  If the bulb breaks, the vaporized mercury can be inhaled or it can settle as a fine powder. 

This is why it is important that, when the CFL stops working, you take it to an authorized disposal site.  These can be found at many stores that sell them or check the county website for locations. 

There have been some concerns about ultraviolet emissions, but, unless you have certain medical conditions, making sure you stay more than one foot away from the bulb is considered safe.  The issue of EMF (electromagnetic fields) has been raised, but this is a concern with all electrical equipment, even power cords.

So, to be safe and environmentally responsible,  assure that CFL bulbs are located as to minimize the chance of breakage and dispose of them properly.
I hope  this answers the question.

Here are two sites with additional info:
http://www.scientificamerican.com/article/are-compact-fluorescent-lightbulbs-dangerous/

http://healthycanadians.gc.ca/drugs-products-medicaments-produits/consumer-consommation/home-maison/cfl-afc-eng.php