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Regular exposure to hair dyes, processing agents, and other chemicals
used in hair salons and barbershops probably increases cancer risk,
according to the
International Agency for Research on Cancer (IARC), a World
Health Organization panel that maintains the world's most commonly-used
system for classifying carcinogens. But there’s not enough evidence to
say whether personal use of these products is linked to elevated risk,
according to the report.
The IARC has labeled these occupations as "probably
carcinogenic to humans," a classification the agency reserves for those
exposures backed by fairly strong evidence. In 1993, the IARC found
that hairdressers and barbers were probably exposed to cancer-causing
substances, but at that time, evidence of an increased cancer risk in
this population was "inadequate." This week's report, published in the Lancet Oncology, is
based on a review of epidemiological studies published since that time.
Some of the products used by hairdressers and barbers--such as
dyes, pigments, rubber chemicals, and curing agents—have been found to
cause tumors in rats in laboratory studies or have been known to cause
bladder cancer in humans. In some studies, increased risk has been
associated with permanent dyes and use of darker-colored hair dyes.
IARC researchers found a small, but consistent, risk of
bladder cancer among male hairdressers and barbers. However, according
to the American Cancer Society's Michael Thun, MD, vice president,
epidemiology and surveillance research, "it was unclear whether that
was caused by past exposure to chemicals that are no longer used or
continuing exposure to ingredients in contemporary products." Some
coloring agents were discontinued in the 1970s because lab studies
revealed they had cancer-causing properties.
"IARC classifications are particularly important for
regulatory agencies that have direct responsibility for workplace
safety," says Dr. Thun. "Workers can reduce skin exposure to these
products by wearing gloves."
Some studies have looked at whether personal use of hair dyes
is associated with an increased risk of bladder cancer, leukemia,
multiple myeloma, Hodgkin disease, non-Hodgkin lymphoma, lung cancer,
breast cancer, oral cancer, and cervical cancer, but according to the
IARC, the evidence for a link thus far is "inadequate."
The IARC's findings on this topic will be published as Volume
99 of the IARC
Monographs. For more information on this topic, see the
American Cancer Society documents, Known
and Probable Carcinogens and Hair Dyes.
ACS News Center stories are provided as a source of cancer-related
news and are not intended to be used as
press releases.
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