Well, it says aspen bedding. Like the kind at the pet store for hamsters. I researched it before using it and I never read anything about it being toxic. That's why I used it. I know cedar is, so I won't even buy that at all even for house things or candles. I've used it after the ri. If it were toxic, wouldn't it have killed him way faster than 5 years?? We did have under the tank heat mats, but they kept unsticking, so we just used lights and kept the room warm all of the time.