Hmmmm - interesting. I have had three dogs in my life time, all of whom had tennis balls. Throwing and retrieving tennis balls is the major activity for all the dogs in our local park. I can see where these days you need to be careful where they are made because of the risk of harmful dyes and yes, occasionally I did have to rescue balls from Louie's mouth when he had chewed them to pieces but otherwise until now I have never heard any concerns about them being dangerous. Louie, by the way was very choosy about his balls and would only play with brand name tennis balls. If they smelled funny, he wasn't interested. It's unwise I think to leave any dog alone with a chew toy other than the kong type heavy duty toys they cant destroy.