Does your shop cut, grind or hone stone dry? If so, you should consider
the fact that the dust created from cutting and grinding certain types
of stone will emit silica in the air. If you or your workers are not
using the proper respiratory protection, you could be exposing yourself
and your workers to serious health problems - and potentially
devastating lawsuits. Breathing silica dust can cause a disease known
as silicosis. More than 250 people each year die from this disease, and
over 1 million workers in the U.S. are exposed to silica dust.
concerns regarding silicosis in the stone industry have been on the
rise lately, the problem is certainly not a new one. In 1998, the
Washington State Department of Labor and Industry specifically cited
the stone fabrication industry as being at risk of silicosis. Its
report read, in part, as follows:
- "Fabricating granite
countertops and other silica-containing materials may expose workers to
levels of respirable crystalline silica above state limits, as was
found recently by the Department of Labor and Industries and the
University of Washington. Workers who inhale excessive amounts of
crystalline silica can develop silicosis, a serious and potentially
fatal lung disease. Methods for controlling exposure to silica are
The really bad news is that there is no cure
for silicosis. The good news, however, is that the disease is very
preventable. The following are some answers to common questions
regarding silica in the stone fabrication shop:
What is crystalline silica?
Crystalline silica is a natural component of the earth’s crust, and it is a basic component of sand, quartz and granite rock.
What stone types contain silica?
All granites, as well as certain slate varieties and some marbles, may
contain harmful silica. I would make the assumption that all granites
and slates contain silica. Most marbles, except for a few green
varieties, have silica. Limestone generally will not contain silica,
although there are a few which may. All quartzites and stone containing
quartz will also have silica.
What are the health hazards of exposure to silica dust?
Crystalline silica inhaled in excessive amounts can cause a serious and
potentially fatal lung disease called silicosis. Silica is also capable
of causing lung cancer with prolonged heavy occupational exposures.
Workers with impaired lung function due to silica exposure are also
more susceptible to other respiratory diseases, such as tuberculosis.
The health hazards of silica are not new; silicosis is one of the
world’s oldest known occupational diseases, with reports dating back to
ancient Greece. These serious health hazards can be caused by
short-term exposure to very high levels of silica as well as long-term
exposure to levels of silica that aren’t quite as high, but still
exceed state limits.
What activities in stone fabrication expose workers to silica dust?
Activities common to stone countertop fabrication - grinding, cutting,
routing, drilling, chipping or polishing granite and other stone
materials containing crystalline silica - can create airborne dust and
the potential for health hazards to workers.
High silica exposures have also been found in other stoneworking operations, such as firms which fabricate stone memorials.
exposure to silica-containing dust is dependent on a number of factors,
including the amount of crystalline silica in the material, which tasks
are being done, length of time performing dusty tasks, work practices
(e.g. dry work or wet work), type of ventilation in use and specific
What are some examples of limits on silica exposure?
In Washington State, for example, the permissible exposure limit (PEL)
for exposure to respirable crystalline silica is 0.1 milligrams silica
per cubic meter of air (0.1 mg/cu.m), averaged over an eight-hour
workshift. This limit can be exceeded in just 10 minutes of “dry” work
on stone products that contain silica. Employers with workers exposed
to silica dust above the legal limit must reduce exposure through a
variety of control options. Employers also need to explain to workers
the health risks of silica exposure and methods they use to eliminate
or reduce exposures.
Most states will have their own exposure
limits for silica, and I would encourage you to check with your state’s
Department of Labor. OSHA also has some excellent information on
silicosis on its Web site: http://www.osha.gov/SLTC/etools/silica/silicosis/silicosis.html
What methods can be used to reduce exposure to silica?
Methods for reducing exposure to silica dust are available. Using water
to suppress dust is perhaps the most effective and often-used control
method. Purchasing water-fed tools, or finding ways to use water at the
point of operation (e.g. a directed water spray or trickling water on
the working surface from a soda bottle with a small hole at the bottom)
should always be considered. Grinders can produce the most dust, and
they have been successfully adapted with a water-feed system. Another
control option would be to purchase or equip grinders and saws with
ventilation devices that capture and route dust to an industrial type
Respirators may be used as a control for very infrequent
tasks or where no feasible engineering controls (e.g. using water or
ventilation) can be found for a particular task. Where respirators are
used (in most cases a half-face respirator equipped with HEPA type
filters), a complete respirator program must be put in place. Such a
program includes proper selection, fit testing, cleaning and
maintenance, supervision, training and written procedures.
What other hazards need to be addressed?
When using water for dust suppression, floor drainage and appropriate
clothing must be considered. Also, the use of electrical equipment with
water requires grounded equipment, ground fault circuit interrupters
(GFCI), electrical cords routed overhead and sufficient maintenance of
electrical tools. The use of air-powered tools can eliminate the
electrical hazards. Handling large pieces of stone necessitates
specific safe work practices to prevent back injuries and potentially
fatal material crashes. An effective accident prevention program
addresses these and other hazards associated with the stone fabrication