Eh, yes, there are concerns, since CONTROL gives them full control on the table. ALTER is slightly better, but that may be bad enough. To you want these users add columns to right and left on these tables?

I think a better solution is to bundle the TRUNCATE TABLE statements in a stored procedure which you sign with a certificate and the create a user from that certificate that you grant the required permissions. Finally grant the users in question permission to execute the procedure(s). For more details, see this article on my web site: http://www.sommarskog.se/grantperm.html