How to determine how many user namespaces are being used

There are two kernel parameters which determine the user-namespaces in Linux. The first one is kernel.unprivileged_userns_clone and the other is user.max_user_namespaces. If we set the value as

then it implies that on the system only 8 user namespaces can be used.

So how to determine the number of user namespaces that are being used on a live system at any instance? And which applications or libraries are using these?