The EPA hosts several different in-house portals to pesticide information and there are a couple of excellent second party portal hosts:
Pesticide Chemical Search is helpful for finding historical and ongoing regulatory and scientific information about specific pesticide active ingredients.
The Pesticide Product Label System provides links to EPA-approved labeling of primary registered products (distributor products will not show up in results)
The Pesticide Product Information System is the full database of EPA-registered pesticides. The database files are mostly useful to people who are familiar with setting up databases.
Perhaps the easiest way to figure out if a pesticide is EPA-registered is to search for it using the National Pesticide Information Center's Product Research Online. NPIC is an EPA information-sharing partner with extensive experience in pesticide-related exposure issues. NPIC NPRO permits searches for all pesticide products, even "distributor products" that have three-part EPA Registration Numbers.
Purdue University's National Pesticide Information Retrieval System is another EPA information-sharing partner NPIRS provides a user-friendly portal to EPA's PPIS database, which allows anyone with internet access to search for pesticides by primary registered product name, Primary company name, two-part EPA Reg. No. or active ingredient. EPA provided initial funding for NPIRS, and we regularly update the PPIS files online.