Actually, the active ingredient, dichloroisocyanurate, is approved by the EPA. However, the EPA approves chemicals for different purposes, like a sanitizer or pesticide or a water purifier. So, that's two questions--what kind of EPA certification are we talking about? And are Aquatabs EPA certified? If the manufacturer, Medentech, doesn't boldly proclaim EPA certification as a water purifier on its own website (they don't), then I assume that it is not certified. Does that lack of certification make it illegal to sell in the US? Actually, I have no idea. I'm not sure which agency has jurisdiction over the import and/or sale of chemical water purifiers.