Which of the following is not a cause of oropharyngeal carcinoma

ETIOLOGY: Smoking: Incidence of oral cancer is six times more in smokers than in nonsmokers. Tobacco chewing: Carcinoma develops at the site of the quid. Alcohol: Cancer of upper aerodigestive tract occurs six times more in heavy drinkers as compared to nondrinkers. Dietary deficiencies: Riboflavin deficiency may be responsible for cancer in alcoholics. Paterson-Brown-Kelly syndrome also called Plummer-Vinson syndrome (iron deficiency anaemia) is responsible for cancer of the oral cavity and hypopharynx. Dental sepsis, jagged sharp teeth and ill-fitting dentures: All these cause chronic irritation and may lead to the development of cancer. Ref: Textbook of ENT, Dhingra; 6th edition; Pg no: 225