A method of forming a filter for a smoking article which includes exposing cellulose acetate fibers to an electron beam process, wherein electron beam process deacetylates the cellulose acetate fibers to render the cellulose acetate fibers water-permeable; and forming a cellulose acetate rod from a tow of the cellulose acetate fibers. Filter plugs of the cellulose acetate fibers are water-permeable and allow discarded filtered smoking articles to rapidly degrade and expose the components to the environment.