Update: Pete Hoekstra seems to suggest here that the shells may be rather more recent than Gulf War I:
Hoekstra said the document is not a “smoking gun.” But he hinted that the chemical agents could be significant because they may have been added to the discovered artillery shells after the first Gulf War. He noted that one of the declassified findings says the munitions could be lethal.
“David Kay says anything produced prior to 1991 is not lethal anymore, so what is the discrepancy here?” Hoekstra said. “I am 100% sure if David Kay had the opportunity to look at the reports that describe these things, he would agree with the finding that … these things are lethal and deadly,” Hoekstra said.