To the OP, since your question really hasn't been answered I thought I'd chime in.
Generally speaking, a bbbj is a risk but far less risky than say, bbfs or even a pussyslide.
From what I recall, from a statistical POV, transmission of pretty much anything to the receiver of a bbbj is far less likely than the giver.
Some may worry that a girl may have cold sores and that may transmit to genital herpes. However, the strain of cold sores and genital herpes is quite different and if I recall correctly, the oral version of the virus doesn't like the skin around ur peepee.
There is a risk of oral to genital gonorrhea though.