How are you planning to connect the relay? If you have the 220V supply going to the common contact and one or both of the other contacts connected to devices to be powered, then if the worst happens and a large mains transient causes a discharge between the two pins, all that will happen is that the transient will reach the device that is supposed to be off. Depending on the application, this very likely doesn't matter.
It's much more important to maintain the 8mm clearance between the 220V pins and the relay coil pins/all the other non-mains circuitry on your PCB/anything the user might be able to touch.