Blue cleaning brush leaves crap in water

[Thunder3]

I notice that the blue glass sponge cleaners after you squeeze the saltwater from them they leave tiny blue particles that would get in your tank if you squeeze out the excess water in it. Is this safe? I am using the API long handle blue brush once and it does it also. I don't think the white acrylics do this but they are not as good at getting off harder algae on glass.