The occupational hazards of working as a hairdresser or barber have been confirmed as probably carcinogenic. This is one of the conclusions of the latest Working Group report of the International Agency for Research on Cancer (IARC), published in the April edition of The Lancet Oncology.
Modern hair dyes are classified as permanent, semipermanent, or temporary dyes. The permanent (or oxidative) hair dyes represent about 80% of the market and consist of colourless primary “intermediates” and couplers, that, in the presence of peroxide, form the dye by a chemical reaction. Dark hair dyes tend to contain the highest concentrations of the colouring ingredients. The use of some such colorants was discontinued in the 1970s after positive cancer tests in rodents.
Dr Robert Baan, International Agency for Research on Cancer, Lyon, France, and colleagues say that many new epidemiological studies on cancer in hairdressers, beauticians, and barbers have been published since the previous IARC assessment in 1993. They say: “A small, but consistent, risk of bladder cancer was reported in male hairdressers and barbers. Because of few supporting findings by duration or period of exposure, the Working Group considered these data as limited evidence of carcinogenicity and re-affirmed occupational exposures of hairdressers and barbers as ‘probably carcinogenic to humans’.” (Group 2A)
The Working Group also reviewed the epidemiological evidence on personal use of hair dyes, but decided that this evidence was inadequate to come to a definitive judgement as to whether or not such personal use could be carcinogenic. (Group 3)
The Working Group also assessed a number of other chemicals, which, like hair dyes, belong to the aromatic amine group of chemicals. Ortho-toluidine, used in the production of dyes, pigments, and rubber chemicals, is now classified as carcinogenic to humans (Group 1), as is MOCA, used as a curing agent in the plastics industry.
Dr Robert Baan, International Agency for Research on Cancer, Lyon, France, T) +33 4 7273 8659 E)
Journal
The Lancet Oncology