Objectives A cluster of 11 cases of cholangiocarcinoma (CC) was recently observed in a small Japanese printing firm. To explore whether the identified cluster is indicative for an elevated risk of CC among workers in the printing industry at large we explored the risk of liver cancer, gall bladder cancer and CC among individuals employed in the printing industry in four Nordic countries (Finland, Iceland, Norway, and Sweden) over a period of 45 years. We used data from the Nordic Occupational Cancer (NOCCA) cohort.
Methods The cohort was set-up by linking occupational information from censuses to national cancer registry data utilising personal identity codes in use in all Nordic countries. We calculated standardised incidence ratios (SIRs) for men and women working in the printing industry, stratified by occupational category (typographers, printers, lithographers, bookbinders).
Results Among men we observed elevated SIRs for cancer of the liver (1.35, 95% CI: 1.14–1.60; 142 cases), specifically intrahepatic CC (2.34, 95% CI: 1.45–3.57; 21 cases). SIRs for liver cancer were especially elevated among printers and lithographers, and SIRs for intrahepatic CC among typographers and printers. SIRs for cancer of the gall bladder or extrahepatic CC were not elevated. SIRs for women followed a similar pattern, but the number of cases was low.
Conclusions The NOCCA cohort has proven useful for an instant investigation following-up a report of a cancer cluster. Our study supports the notion that the finding of excess CC risk among workers in a small Japanese printing firm possibly extends beyond that specific firm and country. Further studies should focus on the specific exposures that occur in the printing industry.
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