What you really want to ask is -- are they 'Achivally Safe'. As stated previously, just b/c it's not acid-free, doesn't mean it's safe. It can be safe for use with photographs. but still not stand up to time.
So, if anything yellows, cracks, becomes brittle over time, then it's something to avoid unless it's for cards or something you don't care about longevity (and even that's relative).
My opinion is that paper towel would not be a good choice for the long term.