Increased cancer risk in male hunters in Northern Sweden after the Chernobyl Nuclear Power Plant accident?

Abstract

Background: Hunters have higher internal radiation exposure due to consumption of game in Swedish counties with high fallout of 137Cs after the Chernobyl accident compared with the general population. Methods: Cancer incidence was studied in nine counties with three deposition categories of 137Cs fallout after the Chernobyl accident in 1986. A total of 9,267 cancer cases occurred in male hunters and 138,909 cancer cases in male non-hunters to 31 December 2015. Directly age standardized cancer incidence and Incidence Rate Ratios (IRR) with 95% Confidence Intervals (CI) were calculated for total cancer and radiation associated cancers, respectively. IRR was calculated between hunters, using the lowest deposition counties as reference, and within counties using non-hunters as reference. Hence, cancer risks of internal radiation exposure and the hunting lifestyle, respectively, could be studied. Results: An increasing trend in total cancer incidence was seen in non-hunters. For hunters this trend was significantly lower up to 2001 when the total cancer incidence crossed over the weaker non-hunter trend and remained higher the following 15 years. A weak exposure response trend for radiation associated cancers was found both within hunter and non-hunter category, respectively. No clear exposure response pattern was seen in IRRs for total cancer in hunters versus non-hunters between counties with increasing 137Cs deposition. IRRs for hunters compared with non-hunters were higher regardless of rural/non-rural status with slightly higher risk estimates in rural areas. The overall IRR for hunters was 1.06 (95% CI 1.04 - 1.08) 1986 - 2015, representing an excess of 531 cancer cases in hunters. No confounding effect from tobacco smoking or education level could be identified. Conclusion: Total cancer incidence was increased for hunters versus non-hunters. However, exposure classification was too crude to exclude an association between cancer and 137Cs. Detailed dosimetry is needed to analyse and interpret any trend.