A treatment fluid composition for treating a subterranean formation penetrated by a well bore is formed from an aqueous fluid, a hydratable polymer and an inorganic peroxide breaking agent, which is classified as a stable, non-oxidizer according to UN standards but which retains oxidizing properties as measured by the content of available oxygen. A method of treating a subterranean formation penetrated by a well bore may also be performed by forming a treatment fluid from an aqueous hydrated polymer solution. This is combined with a stable, inorganic peroxide breaking agent. The treating fluid is then introduced into the formation. An optional crosslinking agent capable of crosslinking the polymer may also be included.