Regular Use of Hair Dye Increases Risk of Bladder Cancer, Study Says

VANCOUVER (CP) - Women who routinely dye their hair - and the hair stylists who apply the colour - have an increased risk of bladder cancer, says a study in the current International Journal of Cancer.

Researchers at the University of Southern California said women who use permanent hair dyes once a month for one year or more double their risk for bladder cancer. After 15 years, the risk is tripled, said the authors of the study which looked at 1,514 bladder cancer patients.

Hairdressers who applied dyes for at least 10 years had five times the normal risk of developing bladder cancer.

Study authors said semi-permanent and temporary rinses were not implicated and could be considered as an alternative.

They may still contain the same chemicals, called arylamines, that are absorbed through the scalp and skin, but the concentrations are considerably lower in both semi-permanent colours and lighter shades, the study said.

The chemicals pass through the bladder and are expelled through urine.

Dr. Nhu Le, a statistician/epidemiologist at the B.C. Cancer Agency, said previous studies have found an occupational risk of bladder cancer among hairdressers.

But the UCLA study is the first to establish a link between salon customers and hair dyes, he said.

It is a puzzle why hairdressers are at higher risk, because they wear gloves when applying colour, but Le said inhaling the strong odours of the chemical compounds in the hair dyes may pose a risk.

Animal studies have found hair dyes have cancer-causing properties, he said.

The study, funded by the National Cancer Institute, is being criticized by the Canadian Cosmetic, Toiletry and Fragrance Association.

The association said in a release that it is reviewing the study but "there are many questions regarding the interpretation of this study and it draws conclusions that are not supported by the data."

Dr. Manuela Gago-Dominguez, the principal author of the study, acknowledged that previous research has not found a strong link between bladder cancer and hair dyes.

"We're the first to say these results need to be confirmed with other studies," she said.

Gago-Dominguez said previous research has drawn a connection between black hair dyes and leukemia and non-Hodgkin's lymphoma, which killed one of the world's most famous dark-haired beauties, Jacqueline Kennedy Onassis.

In the United States, the Cosmetic, Toiletry and Fragrance Association has also attacked the study, noting that while more and more women have been colouring their hair in the past 50 years, there has not been a comparable rise in the incidence of bladder cancer.

One in three women are said to colour their hair in North America, but in Canada, bladder cancer incidence and mortality has been decreasing over the past decade in men and women by about two per cent annually.