The following are risk factors for developing cholangiocarcinoma except -

Cholangiocarcinoma (CCA) is an uncommon tumour that can arise anywhere in the biliary tree, from the intrahepatic bile ducts (20-25% of cases) and the confluence of the right and left hepatic ducts at the liver hilum (50-60%) to the distal common bile duct (20%). It accounts for only 1.5% of all cancers but the incidence is increasing. The cause is unknown but thetumour is associated with gallstones, primary and secondary sclerosing cholangitis, Caroli's disease and choledochal cysts . ref Harrison 20th edition pg 567