It's ridiculous how the military could be allowed to just up and leave.
However it's been monitored since 2016 and Denmark has paid the bill for cleaning up some of it already.
The latest assessment from 2021 said that it'd be alright until 2100. Could probably be sooner now, but anyway, it's so far up north that a whole lot of Greenland needs to melt before it reaches the pollution, so we'll get a heads up in good time. And yes, there will likely be other even more serious issues if that happens.
Here's a video from 2016 which shows what it looks like. https://youtu.be/54TJORwhttM?si=ysehIUTrL6-CmuRF