From Directions Magazine, whose reviewer writes:

http://apb.directionsmag.com/entry/esri-lauches-arcgis-open-data-site/388413

Sunday, March 09, 2014
Esri Lauches ArcGIS Open Data Site

“Esri has launched ArcGIS Open Data, a website with the tag line “Explore open data from all over the world.” Those who visit are invited to: Collaborate, Discover New Data and Visualize and Analyze. Sunday afternoon (March 9, 2014) the website had 81,301 datasets.

“I did a search on EPA since I know the EPA was a participant in the first discussions of ArcGIS Online Open Data Program (Directions Magazine coverage). What I found were many EPA datasets (286) with creation dates in the past few years. There was no informatoin about when the dataset was added to this portal. Alongside a paragraph of description I found these data associated with ctdphonline: EPA Faciliites:”