As of June, 2010, EPA has decided that endosulfan, the active ingredient to Thionex, poses too great a risk to workers and wildlife. Therefore EPA is taking action to end all uses of the product. You can read more about it at: http://www.epa.gov/pesticides/reregistration/endosulfan/endosulfan-cancl-fs.html.
According to an EPA news release dated 6/9/2010, "Makhteshim Agan of North America, the manufacturer of endosulfan, is in discussions with EPA to voluntarily terminate all endosulfan uses. EPA is currently working out the details of the decision that will eliminate all endosulfan uses, while incorporating consideration of the needs for growers to timely move to lower-risk pest control practices."
I do not know anything more at this time, but will keep you posted.