Rust in salt, is it safe?
Rust is iron oxide.  The body needs some iron.  We all drink some rust from pipes.  

To be toxic the only number I found is 200 milligrams per kilogram is lethal. But I have a degree in chemical engineering and I am not sure what they mean by that.  

As for iron the lethal dose is about 45 mg / day. 

Just saw the picture - not enough to hurt you.