The US Environmental Protection Agency has established a Central Data Exchange (CDX) to serve as "a central point which supplements EPA reporting systems by performing new and existing functions for receiving legally acceptable data in various formats, including consolidated and integrated data." XML is identified as the preferred format for data submission, though flat-file and EDI formats are accepted. With the cooperation of several states, information is sent to the legacy systems and made available for wider access. Several provisional XML DTDs, XML schemas, and data dictionaries have been developed. Critical environmental data on EPA facilities, air, water, waste, and toxic substances are submitted via XML and posted to the central CDX database. Specifically, CDX "provides production data flows for the Toxic Release Inventory (TRI), National Air Emissions Inventory (NEI), and Unregulated Contaminant Monitoring Rule (UCMR). Several others including Interim Data Exchange Format (IDEF) for the Permit Compliance System (PCS), submissions under the Toxic Substance Control Act (TSCA), the Resource Conservation and Recovery Act (RCRA), [and Safe Drinking Water Accession and Review System (SDWARS)] are in development." The EPA is also developing an XML-based Environmental Data Registry (EDR) for defining data elements mapped to XML element types. The EDR is "a comprehensive, authoritative reference for information about the definition, source, and uses of environmental data supporting the creation and implementation of data standards designed to promote the efficient sharing of environmental information."

The CDX Implementation Guidelines (IG) for UCMR explain the methods of interacting with SDWARS through CDX The EPA's UCMR XML application is presented in "EPA Implementation Guidelines for SDWARS/UCMR. Volume IV: XML Format." It "documents the specifications for submitting data for the Unregulated Contaminant Monitoring Rule (UCMR) program to the U.S. Environmental Protection Agency (EPA) using Extensible Markup Language (XML) standards. Only laboratories that are registered with EPA's Central Data Exchange (CDX) can submit data to the Safe Drinking Water Accession and Review System/UCMR (SDWARS/UCMR), the information system that supports the collection of data for the UCMR." Appendix A provides the UCMR XML DTD, Version 2.1. Appendix B supplies a UCMR File Structure Tree Diagram. Appendix C contains the UCMR Data Dictionary: XML DTD, Version 2.1. Appendix D provides an UCMR XML Instance (an example XML file based on the UCMR XML DTD, Version 2.1).

Under the Environmental Data Registry, "XML tags will be established for all EPA standard data elements. [As of 2002-04] a draft set of XML tags for the data elements included the final EPA data standards is under review. These tags will be registered in the EDR as alternate names for the data elements and can be found on the data element detail page for each of the EPA data standards. An XML tag name will be identified with the Name Context of 'Draft XML tag.' The XML tags proposed for standard data elements are draft and subject to further development. Those using these tags should be sure to deploy them in systems and business processes that can be readily changed or modified to reflect the evolution of the data element tag formation conventions.