I think you miss read what I wrote.
I said the “fallout of the nuclear explosion would contaminate large part of Europe.” That is evidently similar to an indirect attack on Nato. Nuclear fallout coming with the winds over EU/NATO has the same disastrous effect as a “dirty nuke”.
The rule is if Nato is hit by the effect of such human life destructive nuclear winds - it triggers NATO’s response. NATO’S response could be conventional though.
But still, the response would be certain.
I doubt any response would be military in nature - even the use of conventional forces in response could prompt the use of additional nuclear weapons. Once nukes have been used, politicians will be looking for any & every excuse to avoid escalation. Any response would likely be limited to the standard public declarations of outrage...
;>)