Interestings articles. I've also read that first one before, though not the second. I still stand by my prior thoughts of pine being somewhat harmful, despite what has been posted. While some tests either way would be nice, I can take from simple observation that it isn't that great either. I've seen horses with sensitive systems unable to be kept on pine, as well as I've seen definite improvements in a rats overall health when kept off it. Same frequency of cleaning, same diet, same temperatures, etc. In fact, I clean even less when using substrates such as Carefresh, and have only seen improvements. Overall though, it isn't a severe problem, and I see no problems with keeping feeders on it, since they are not living that long anyways. I don't use it for my pets though, with the occassion of running out of their own substrate