Silica is powdered quartz, in particles so small
they can be inhaled deep into the lungs. The Occupational Safety and
Health Administration (OSHA) estimates that 2.2 million people in
the U.S. are exposed to silica at work, including 1.85 million
Other occupations carrying a risk of silica exposure include
sandblasting, mining, stone grinding, as well as ceramic and glass
manufacturing. Dental assistants may be exposed if they grind
silica-containing casts and porcelains.
Silica has long been known to cause silicosis, and evidence now
confirms that silica exposure can cause lung cancer as well, Kyle
Steenland of Emory University in Atlanta, a co-author of the new
report, told Reuters Health.
Silicosis causes varying degrees of breathing difficulty, and there
is no cure or treatment. Recent research has also shown that
non-smokers can get lung cancer from silica exposure, and that
people who develop silica-related lung cancer don't always have
silicosis, Steenland and his colleague Elizabeth Ward of the
American Cancer Society note.
OSHA is planning to lower permissible levels of silica exposure from
0.1 milligrams per cubic meter of air to 0.05 mg/m3, which the
agency estimates will save 700 lives per year, and prevent 1,700
cases of silicosis annually. The current standard dates back to
The preferred approach to reducing silicon exposure is to use less
hazardous materials, ventilate work areas where silicon dust is
produced and use water-based methods so dust can't escape into the
air, Steenland said.
"Respirators may be useful for workers in short-term high exposure
situations, but are generally not recommended as the primary means
of exposure control due to worker discomfort, difficulties in
communicating with others, lack of compliance and enforcement, and
the fitting and maintenance requirements," Steenland and Ward write
in their report, published in CA: A Cancer Journal for Clinicians
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Anyone who has been exposed to silica and smokes should quit,
Steenland said in an interview. Smoking aggravates the carcinogenic
effects of silica, and smokers with high silica exposure can cut
their risk of lung cancer up to five-fold by quitting, according to
the new report.
People with a history of silica exposure may also qualify to undergo
screening for lung cancer using CT scanning, the investigators note.
OSHA recently extended the public comment period for the proposed
silica exposure rule to Jan. 27.
While there is always a balance between worker protection and
employers' interests, "I'm fairly confident that this standard will
be put into place," Steenland said.
CA: A Cancer Journal for Clinicians, online Dec. 10, 2013
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