I'm guessing the >1% and the 1-3% are just those "Manufactured in a facility containing Silica sand" estimates but you're probably right. If there's any, he freshwater and saltwater soaks would probably eliminate most of not all of that.That is a big percent. It will be avoided. It's probably safe to assume the >1% of quikrete Portland is taken care of in the fresh and salt water baths.