I'm inclined to recommend you not mention it at all. If he hasn't died of it yet, chances are he's not going to, and you know how that brush should be dealt with from now on.

On the other hand, I don't really care for the guy, and so, while I would not directly piss in his cheerios, I would not feel put out if piss somehow came to be in his cheerios. As it were. So my advice may not be what a good person would do.