Introduction Urinary bladder cancer risk in coal miners is currently under debate. We report on a recently performed study in 2 departments of urology in Dortmund, a centre of the former underground hard coal mining industry in Germany. In the greater Dortmund area in the 1990s when coal, iron and steel industries were still active, 70% of bladder cancer cases were glutathione S-transferase M1 (GSTM1) negative, compared to 54% in unexposed controls.

Methods A total of 400 bladder cancer cases and 442 controls with benign urological diseases but without a history of malignancies, were assessed by questionnaire from July 2009 to July 2013. Furthermore, all patients were genotyped for polymorphic enzymes relevant for bladder cancer like glutathione S-transferase M1 (GSTM1) and N-acetyltransferase 2 (NAT2).

Results More than ten years after closure of these industries, the frequency of the GSTM1 negative genotype decreased to 52%, which is a normal finding in general population (OR 0.96, 95% CI: 0.73 to 1.26; smokers: OR 0.93, 95% CI: 0.66 to 1.30; non-smokers: OR 1.02, 95% CI: 0.58 to 1.80). However, former hard coal miners had still an elevated bladder cancer risk (hospital A: 20 bladder cancer cases (10%) and 8 controls (3%) (OR 3.22, 95% CI: 1.39 to 7.49); hospital B: 32 cases (16%) and 20 controls (10%) (OR 1.72, 95% CI: 0.95 to 3.12). The slow N-acetyltransferase 2 status, which is associated with an increased bladder cancer risk in persons formerly exposed to aromatic amines, was normal in hard coal miners with bladder cancer in all three studies in the Dortmund area.

Conclusion After closure of the coal, iron and industries in the 1990s, GSTM1 negative genotype is currently no more a relevant bladder cancer risk factor. However, an elevated bladder cancer risk in former hard coal miners is still observable.