Permanent Hair Dyes and Bladder Cancer Risk

The study by Dr. Henley and Dr. Thun from the ACS/CSP-II cohort found no link between permanent hair dye use and bladder cancer mortality, regardless of smoking status. However, a case-control study from Los Angeles suggested a potential causal relationship between hair dye use and bladder cancer risk, particularly among women with the NAT2 slow acetylation phenotype, which affects the metabolism of carcinogenic aromatic amines found in hair dyes. The Los Angeles study, involving 203 female cases and controls, indicated that smokers using permanent hair dyes had the highest risk, suggesting an additive effect of smoking and hair dye use on bladder cancer risk. The findings highlighted a discrepancy with earlier studies, possibly due to differences in study design and population characteristics.