Sad thing is almost any coin will oxidize, tone, etc. in any folders unless you store them inside something else (i.e. plastic that is coin safe) that is either vacuum sealed or at least as air and water tight as you can get it and use desiccants for humidity control. As far as if you are concerned that the paper and cardboard in the materials will damage a coin. I also have never had problems but I've also only been using littleton folders for circulated and only for about 6 years now. The paper is "archival" or "museum" quality which basically means that the paper used is sulfer free and the pages themselves after making them are coated to prevent the breakdown and escape of gases or chemicals that could cause damage.
