the way our Gov. is, if it was considered not safe, they would ban it or tax it
they are safe, do a google search on exploding refilled 1lb tanks, you will see no problem
and as for unsafe to transport, it's because the seal is meant for one time use and not to be refilled, because you can not be sure the seal will hold transporting in a trunk or inside a car could be bad..again try to find if it has ever happened by googling
I have had some that do not seal after filling, you hear them hiss so you know there is a problem, I put themon the heateror lantern right away and problem solved
I also have some old propane torches that I screw on them to double secure them, over kill but what the heck