In a new study, hairdressers who often used light colored hair dyes or hair-waving products on clients had more potentially cancer-causing compounds in their blood than hairdressers who used the chemicals less frequently.
The study included hairdressers as well as women who used hair dyes on themselves and some who had never used them at all, and none of the women had actually been diagnosed with cancer.
The World Health Organization considers hairdressing work probably carcinogenic, since hairdressers tend to be at higher risk for bladder cancer. The new results could help narrow down specifically where the cancer-causing agents are coming from.
Researchers studied nearly 300 hairdressers, 32 personal dye users and 60 non-dye users for comparison. The participants, all non-smoking women, had their blood tested for several potentially carcinogenic compounds called aromatic amines.
Overall, hairdressers did not have more of these compounds in their blood than either of the other groups.
But within the group of hairdressers, certain compounds were more common among those who gave hair-waving treatments weekly or several times per week compared with those who used the products less often.
Specifically, toluidine compounds in the blood increased with exposure to perm chemicals and permanent light hair dyes.
“The measured levels of o-toluidine in blood among hairdressers were in general low, however, exposure to o-toluidine should be kept as low as possible since it is a carcinogenic compound,” said Gabriella M. Johansson.
Johansson worked on the study at Lund University in Sweden.
Toluidines were long used as the basis for many dyes and are confirmed carcinogens in animals, according to the American Conference of Governmental Industrial Hygienists.
The National Institute for Occupational Safety and Health says the compounds are potentially carcinogenic in humans and recommends occupational exposures to toluidine be kept to the lowest feasible amounts.
The researchers selected one commercially available hair-waving product and tested it for toluidines, which they found in the fixative and the mixture of fixative and perming lotion.
Semi-permanent hair dyes did not seem to increase toluidine exposure, according to results published in the journal Occupational and Environmental Medicine.
“In the late 1970s, regulatory actions were taken in (Europe) and carcinogenic aromatic amines were forbidden for use as hair dye ingredients,” Johansson told Reuters Health by email. “Whether this still is a problem for modern hair dyes is debated.”
The carcinogens in hair products should have been eliminated about 40 years ago, and today most hair products in North America and Europe are similarly safe, said Dr. Carlo La Vecchia of the Istituto di Ricerche Farmacologiche "Mario Negri" in Milan, Italy.
La Vecchia, a cancer researcher, was not part of the new study.
“My point is that these should not be associated with cancer risk,” he told Reuters Health. And since this study is the first of its kind, it will need to be confirmed before researchers can say hair products still may be carcinogenic, he said.
“If some of the findings of this study are confirmed, this should be an indication for change in composition of hair dyes, but it’s far from definite,” he said.
Most of the analyses conducted in the study did not clearly link hair products to potentially carcinogenic compounds, he noted. What’s more, in the past, dark hair dyes were considered more dangerous because they tend to contain more chemicals than light dyes, he said.
“That’s another strange finding of this study,” he said.
Johansson said her team will continue with an analysis of light and dark hair dye products, looking for the same compounds they found in hairdressers’ blood.
In the meantime, hairdressers should use gloves to minimize their exposure to chemicals in dyes, and should change to fresh gloves after mixing the dye, applying it and rinsing it, she said. Since many hairdressers think it is difficult to cut hair with gloves on, they should cut before coloring, not after, she said.
Even if the carcinogen results are not confirmed in other studies, taking these precautions is a good idea, La Vecchia said, because hair chemicals do contain toxins and irritants.