Dear Donia,
How long would it take 24-hour exposure to fluorescent lighting to damage a book jacket protector?
Q. Dear Donia,
What an interesting question but unfortunately one that is difficult to answer as there are more variables involved than light alone. I would not think that several months would cause that much damage, but it could be possible. A few things to consider:
Do you know the composition of the plastic (is is polyester, polyethylene, or something else)?
What was the temperature and relative humidity in the library while the lights were on?
Were the jackets that are disintegrating closer to the lights or were they randomly distributed throughout the shelves?
Are the jackets all from the same supplier and if so, who is the supplier? They may be able to give you more insight as they would know the exact composition.
These are the questions I would start with to begin solving this mystery.
Good luck with the detective work!