preposition

on the subject of or in connection with; about.

we are given little information concerning matters of national security

about,regarding,on the subject of,relating to,relevant to,with regard to,as regards,to do with,with reference to,referring to,with respect to,respecting,as to,touching on,in the matter of,in connection with,re,apropos of,anent

adjective

causing anxiety; worrying.

I find many of the comments very concerning