Cut filler compositions, cigarettes, methods for making cigarettes and methods for smoking cigarettes which involve the use of partially reduced nanoparticle additives capable of acting as an oxidant for the conversion of carbon monoxide to carbon dioxide and/or as a catalyst for the conversion of carbon monoxide to carbon dioxide are provided. The compositions, articles and methods of the invention can be used to reduce the amount of carbon monoxide and/or nitric oxide present in mainstream smoke. The partially reduced additive can be formed by partially reducing Fe.sub.2O.sub.3, to produce a mixture of various reduced forms such as Fe.sub.3O.sub.4, FeO and/or Fe, along with unreduced Fe.sub.2O.sub.3.