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
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
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.”
[to top of second column]
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
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.
Occupational and Environmental Medicine, online June 9, 2014.
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