I don't see oxidation as a safety consideration. However, it certainly leaves a pipe totally unappetizing to me. I was gifted with a Thompson Cigar house pipe, a fine piece of briar done as a handsome freehand, but the stem oxidized almost as soon as it was re-polished. I had a new acrylic stem made for it, tortoise shell replacing the original black Vulcanite, and it looks and smokes far better than before. Also the old stem had a version of a P-lip bit. I have one of those on a Peterson that I enjoy, but it retains its polish.