I learned in the A & P course that ear wax (or cerumen) is a waxy secretion by ceruminous gland (= modified sebaceous gland), mixed with sloughed epithelial cells, which inhibits the growth of certain bacteria due to its acidic pH. It also protects the skin of the external auditory canal by providing a waterproof layer, so, it's something beneficial to us.
Sure enough, there appear to be a number of articles written to support this - "Bactericidal activity of cerumen", Chai & Chai (ref 1), "Bactericidal activity of wet cerumen", Stone & Fulghun (ref 2), etc. (though this concept is refuted by a later study! (ref 3))On the other hand, I could find only very few articles that discuss the role that ear wax plays in disease transmission or as a portal of exist for pathogens. I started with an article by Kemp & Bankaitis (ref 4), in which it is stated that cerumen is not considered an infectious agent until it becomes contaminated with blood or mucus, and it can even be placed in the regular trash unless significant amount of blood or mucous is present.
So, it appears the danger is not in cerumen itself but in blood/mucous contaminant. CDC lists Hepatitis B, Hepatitis C, HIV and Viral Hemorrhagic Fever(VHF) as infectious diseases by bloodborne pathogens (ref 5).
On the topic of cerumen itself transmitting bloodborne viruses, I could find only two articles, both by the same group of researchers, Beyindir, Kalcioglu et al. First article is on the study of possible transmission of Hepatitis B (ref 6), in which the authors conclude that cerumen can be a potential source of transmission and further investigation for horizontal, nosocomial, and occupational transmission is necessary. The second article is on Hepatitis C, and it concludes that cerumen has no risk, even in patients with high HCV RNA serum levels. I could not find any articles to confirm/deny cerumen as a source of transmission for HIV or VHF.
I think our text book lists ear wax as a portal of exit for pathogens, because of more than minimal potential risk of contamination by blood, during treatment of otitis, removal of impacted ear wax etc. performed by otolaryngologists/audiologists on a regular basis.
Referrences-----------1: Antimicrobial Agents and Chemotherapy, 1980 Oct;18(4): 638-412: The Annals of otology, rhinology, and laryngology, 1984 Mar-Apr;93(2 Pt 1): 183-63: "Influence of human wet cerumen on the growth of common and pathogenic bacteria of the ear", Campos, Betancor, et al., The Journal of laryngology and otology, 2000 Dec;114(12): 925-94: "Infection Control in Audiology", http://web.clas.ufl.edu/users/sgriff/infectioncontrol.pdf5: http://www.cdc.gov/ncidod/hip/Blood/blood.htm6: "Does cerumen have a risk for transmission of hepatitis B?", The Laryngoscope, 2004 Mar;114(3): 577-807: "Detection of HCV-RNA in cerumen of chronically HCV-infected patients", The Laryngoscope, 2005 Mar;115(3): 508-11