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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.
A PSE&G technician was at my house to charge the freon in my AC. He told me that I've got a leak & that I'll have to get a whole new unit. This seems a little far-fetched to me, especially because my unit is only 10 years old.