Background Following the indication of the United Nations Environmental Program, several cohort studies have explored cancer incidence among the military personnel involved in peacekeeping operations in the aftermath of the Balkan war, allegedly involving exposure to depleted uranium (DU). Concern was raised in the media about excess cases of specific cancer sites in these studies.

Methods Five follow up studies of cancer incidence were conducted among the peacekeeping cohorts from Italy, Sweden, Denmark, Norway and the Netherlands. We conducted a metanalysis of their results on overall cancer, solid tumours, and cancer of the lymphohaemopoietic system. A metanalysis of Hodgkin lymphoma incidence was limited to the three studies that analysed specifically this neoplasm. Fixed and random effect estimates (FES and RES respectively) were calculated, and heterogeneity of findings across studies was evaluated.

Results Risk of overall cancer was not elevated in the Balkan peacekeeping cohorts (FES = 0.8, 95% CI: 0.7–1.0), as it was the case for solid tumours (FES = 0.9, 95% CI: 0.7–1.1), with significant heterogeneity across studies, due to a significantly decreased incidence of solid tumours in the Italian cohort. Risk was also not elevated for cancer of the lymphohaemopoietic system (FES = 1.1, 95% CI: 0.8–1.4). A non significant increase in Hodgkin lymphoma incidence was observed (FES = 1.8, 95% CI: 0.8–4.1), mostly explained by the excess observed in the Italian cohort. No heterogeneity was detected for risk of lymphohaemopoietic neoplasms and Hodgkin lymphoma. Results did not change when considering the RES results.

Conclusions Exposure to DU was discarded in these cohorts, further in depth analysis is warranted to understand the circumstances leading to the excess incidence of Hodgkin lymphoma among the Italian cohort.