Objectives: Previously, the author reported a cluster of 11 cholangiocarcinoma cases exposed to 1,2-dichloropropane (1,2-DCP) and/or dichloromethane (DCM) in an offset proof-printing company. Before that report, the association between the two chemicals and cholangiocarcinoma had not been known. The current study describes two cholangiocarcinoma patients exposed to 1,2-DCP or DCM in different offset printing companies. Methods: The author obtained medical records for the patients, and interviewed the surviving patient and a relative of the deceased patient about their occupational history. Results: Case 1 was a man born in 1950. He worked in the printing section in a proof-printing company for 26 years. He was diagnosed as cholangiocarcinoma in 1998 and died in 2000. In proof-printing operations, he used gasoline for 14 years and 1,2-DCP for 11 years to remove ink from a rubber transcription roller (blanket). The exposure concentration of 1,2-DCP was estimated to be between 72 and 5,200 ppm. Case 2 was a man born in 1963. He worked in the printing section in a general offset printing company for 11 years. He was diagnosed with cholangiocarcinoma in 2007. In printing operations, he used both kerosene and a mixture of 50% DCM and 50% 1,1,1-trichloroethane (1,1,1-TCE) for 11 years to remove ink from a blanket. The exposure concentration of DCM was estimated to be between 240 and 6,100 ppm. He was simultaneously exposed to similar levels of 1,1,1-TCE. Conclusions: Because the offset printing process may cause cholangiocarcinoma, occupational history should be examined for patients with this cancer.(J Occup Health 2014; 56: 164-168)

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