U.S. Patent 6,782,892, assigned to Philip Morris USA, Richmond, Virginia, USA. Cut filler compositions, cigarettes, methods for making cigarettes and methods for smoking cigarettes which involve the use of manganese oxide mixtures that include nanoparticle manganese oxide and other nanoparticle additive(s) capable of converting carbon monoxide to carbon dioxide and/or converting nitric oxide to nitrogen. 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 reaching the smoker and/or given off in secondhand smoke. The manganese oxide can be co-precipitated with the additive(s), or mechanically mixed with the additive(s) to form the manganese oxide mixture. The manganese oxide may have a lower light-off temperature than the additive, such that during smoking of the cigarette, the heat generated from the oxidation of carbon monoxide by manganese oxide is capable of activating the additive. The additive may include iron oxide nanoparticles.