Cancer risks in hairdressers: assessment of carcinogenicity of hair dyes and gels.

More than a decade ago, an increased risk for bladder cancer among male hairdressers was established. Frequent changes of hair dye formulations together with their widespread use call for safety guarantees. We carried out a follow-up study of a cohort of 38866 female and 6824 male hairdressers from Sweden and analyzed all of their malignancies over a period of 39 years. Standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) for 28 cancer sites were calculated using the economically active population as a reference. During the years 1960-1998 a total of 1043 cancer cases were recorded in male hairdressers. Excess risks for cancers of the upper aerodigestive tract and lung and colorectal adenocarcinoma were observed. Additionally, male hairdressers working in 1960 had an increased risk for urinary bladder cancer, which was highest in the 1960s with an SIR of 2.56 (95% CI 1.36-4.39) and decreased with the follow-up time. A total of 2858 cancers were recorded in female hairdressers. An increased risk was observed for cancers of the pancreas, lung and cervix and in situ cancer of the skin. The increased risk for in situ skin cancer specifically affected the scalp and neck, sites of contact for hair dyes, with an SIR of 2.43 (95% CI 1.14-4.44). The increase in lung cancer, the only site for which cancer was increased in either sex, may depend on confounding from smoking. Bladder cancer was not increased among hairdressers in the recent decades and is therefore not likely to be associated with modern hair dyes.