Compositions and methods for destroying chemical and biological agents such as toxins and bacteria are provided wherein the substance to be destroyed is contacted with finely divided metal oxide nanoparticles. The metal oxide nanoparticles are coated with a material selected from the group consisting of surfactants, waxes, oils, silyls, synthetic and natural polymers, resins, and mixtures thereof. The coatings are selected for their tendency to exclude water while not excluding the target compound or adsorbates. The desired metal oxide nanoparticles can be pressed into pellets for use when a powder is not feasible. Preferred metal oxides for the methods include MgO, SrO, BaO, CaO, TiO, ZrO, FeO, VO, VO, MnO, FeO, NiO, CuO, AlO, SiO, ZnO, AgO, the corresponding hydroxides of the foregoing, and mixtures thereof.