Troy Polamalu on dirtiest players list?

Alright, I'm a Steeler fan, but I'm not being biased when I ask: How the hell is Troy Polamalu 9th on the dirtiest players in the NFL list? I understand Hines Ward is (which is a redundant argument because he is a small, old wide reciever), but Troy? I guess that if you're the best they label you dirty. What do you think?