UV in fluorescent bulbs escapes directly through the phosphor itself. No phosphor is 100 opaque to UV, nor does any phosphor convert 100% of UV to visible light

UV in fluorescent bulbs escapes directly through the phosphor itself. No phosphor is 100 opaque to UV, nor does any phosphor convert 100% of UV to visible light. Some phosphor coatings might be better than others, but they will all leak a certain amount of UV.