Fig. 2

Dose-response relationship of exposure to tobacco with deaths owing to extrahepatic cholangiocarcinoma. a Pathology-based analysis; b Non-pathology-based analysis Control defined as no exposure to any tobacco use; Expo 1 defined as exposure to either passive or active smoking only; Expo 2 to 4 defined as combined exposure to both passive and active smoking with fewer than 400, 400–799, and 800 pack-years squared or more, respectively. Risk ratios adjusted for age, gender, urban or rural residence, ethnicity, and education (Model 2)