Vein: A blood vessel that carries blood that is low in oxygen content from the body back t... See the entire definition of Vein Viral: Of or pertaining to a virus.
This means that breathing low concentrations of freon from a leaking refrigerator or air conditioner over a long period of time is unlikely to have a cumulative effect, and thus few, if any, long term health effects.
I foolishly did not have the level of freon checked for the last 3-4 years. Today, I had the system recharged with 8 lbs of freon. During the fill, the technician visually observed the unit for signs of an obvious leak, while also monitoring the stability of the newly added freon.