Jute from burlap bags, sisal, rags, cigarette filters, and carpet scraps find their way into wool bags or bales. When cigarette filters shred into wool, their synthetic fibers look like the rest of the fiber, but do not dye like wool. Polypropylene is a major contaminant and is used in baling twine, tarps, feed bags and used or torn wool packs. Some hay balers cut short ends of twine as each bale is tied and these short pieces drop in the field and eventually find their way into the fleece when the fields are pastured. The operators of tub grinders and pellet mills do not always remove the polypropylene twine when ground hay is included as a pellet ingredient and it can then pass through the sheep's digestive system to contaminate the wool.
Polypropylene disintegrates and causes major contamination in the finished textile product.
Applied contaminants are used for identification or disease treatment practices and include paint brands, dewormers and parasite sprays. In the United States, shearing facilities vary from tents set up in corrals, shearing trailers, and permanent sheds. On the farm, barns are usually the designated shearing area. The area should be large enough to accommodate the number of shearers required. The space should be well lit and ventilated, and free of drafts that can blow parts of the fleece off the shearing board.