Background The International Agency for Research on Cancer has recently classified 1,2-dichloropropane as carcinogenic to humans (Group 1) based on a small cluster from an offset printing plant in Osaka, Japan, where a high proportion of the employees were diagnosed with the rare cancer cholangiocarcinoma. Because 1,2-dichloropropane has not been used in Europe, including Denmark, it is of interest to explore if this exposure alone can explain the increased risk of choloangiosarcoma within the offset printing plant.

Materials We identified from the Danish Cancer Registry 2,604 male and 3,872 female cases of choloangiosarcoma, born between 1907 and 1987 and diagnosed between 1978 and 2013. Based on the unique personal identifier provided to all residents in Denmark we linked with information on employment history from the nationwide Supplementary Pension Fund database, which keeps information on dates of start and end for each employment, including type of industry, for all employees in Denmark since 1964. Each case was individually matched on birth year and sex with four cancer free controls randomly selected from the Central Population register. Odds ratios (OR) were estimated based on conditional logistic regression and adjusted for SES.

Results Overall, the OR for choloangiosarcoma was 1.4 (1.1–1.7) for men employed for over one year in the Danish printing industries, and 1.8 (1.2–2.9) for women. A tendency of increasing OR’s occurred by increasing duration of employments. Some variation in OR’s arose within different types of printing companies, i.e. from 1.1 (0.8–1.4) in men employed in newspaper production to 3.8 (1.9–5.4) for women in offset printing plants.

Conclusion There is an increased relative risk of choloangiosarcoma in both men and women employed in the Danish printing industry at large, including in most subtypes of the industry, suggesting that other exposures than 1,2-dichloropropane may play a role for the observed elevated risk.