I was given some fairly good potting soil from a friend but he had put it into some polypropylene bags (like cheap, reusable grocery bags) that he had got from a Hi Fi show. The bags were made in China so I'm worried that they contain lead. They have a Cpsia tracking number but I don't know if that means they've been tested for lead and they're safe or what that means. Should I just dump the soil or should it be safe to use?