Respirable Crystalline Silica from Sand Mining
Sand Mining in Wisconsin
Sand mining is not a new practice in Wisconsin. The recent demand for
high-quality quartz sand for a natural gas drilling process called hydraulic
fracturing (also known as “fracking” or “fracing”), however,
has greatly increased this activity – especially in Western Wisconsin. While
Wisconsin has deposits of sand that are used for the hydraulic fracturing
process, the drilling occurs in shale deposits containing oil and natural
gas that are found in other states, such as Texas, North Dakota and
Pennsylvania. Sand mining operations designed to mine and export ‘frac sand’
are often much larger in acreage than the smaller, more traditional
Wisconsin sand mines that serve mainly local needs for sand. The sand is
desirable for fracing and some other uses due to its size, shape, and
crystalline silica properties and because the deposits are usually close to
the surface and easy to mine. An increase in the number of new requests for
mining and processing plant permits has led several communities to raise
questions about the possibility for respirable crystalline silica (RCS) to
be generated at mine sites, and how RCS might impact the health of nearby
What is respirable crystalline silica (RCS)?
Dust can be made up of visible (larger) and microscopic (smaller)
particles. Particulate matter is defined as airborne material (solid or
liquid) that is smaller than 100 microns (millionths of a meter) in size.
For comparison, human hair is typically between 70 to 100 microns in
diameter. The size of the particulate matter affects how long the particles
can stay airborne and how far particles can travel before settling out onto
surfaces. Smaller particles stay airborne longer and thus can travel further
than larger particles.
Respirable crystalline silica (RCS) refers to particles of crystalline
silica less than four microns in size, or particulate matter 4 (PM4).
PM4-sized particles can penetrate deep into the lungs, where the most
critical effects of RCS– silicosis and cancer – are thought to occur.
What are the health effects of RCS exposure?
Inhaled RCS damages lung tissue and can cause a variety of health
problems, including silicosis, increased risk of lung infections,
obstructive lung disease, and lung cancer. These types of lung problems,
especially silicosis, are among the oldest, best documented, and most
understood of occupational diseases. Lung damage progresses over time from
breathing dust released when rocks are crushed or cut. Silicosis is a
chronic, progressive, and inflammatory disease that causes scarring of the
Almost all of the information about the health effects of RCS exposure
comes from studies of workers who were exposed to high levels of RCS at work
for many years. In certain cases, there have been non-occupational
study (exit DHS) found high levels of airborne silica (measured as quartz dust) in
a village in India from uncontrolled rock cutting and grinding operations in
pencil manufacturing facilities. A few published
studies (exit DHS)
have also implicated chronic exposure to
desert dust (exit DHS) in cases of non-occupational lung disease.
What are the potential sources of RCS during sand mining?
In Wisconsin, most sand is mined by excavating sandstone formations that
are near the surface or by dredging deposits of sand. After the sand is
mined, it is washed, sorted by particle size, and stored until it is
transported off-site. Some sand is also coated with polymers or otherwise
treated to improve its properties for hydraulic fracturing applications. If
specific dust-reduction controls are not in place at the mines and
processing plants as well as during transport, there is the possibility for
silica dust and RCS to be released into the air during each of these
processes. Regulations and best management practices are in place in
Wisconsin to protect workers, as well as the public, from any dust created
during the mining, processing, and transport of sand. Some of those existing
control measures are discussed below.
What control measures exist to reduce RCS exposures around mining
The U.S. Mine Safety and Health Administration (MSHA) requires sand mine
operators to control and manage worker exposure to silica dust and RCS. The
Wisconsin Department of Natural Resources requires a fugitive dust control
plan under Wisconsin Administrative Code, Section NR 415.075(2) before the
facility begins operation. Although DNR does not specifically regulate RCS,
the fugitive dust control plan outlines how a facility will reduce or
eliminate all sizes of dust emissions.
Dust control measures that comply with MSHA or DNR requirements might
include indoor storage of sand; the use of tarps, covered trucks and rail
cars; the application of water or other dust suppressing sprays; and other
mechanical control devices. These measures help reduce emissions of silica
into the ambient air and limit exposure of workers and the public to RCS.
What other concerns are raised by communities near newer sand mining
In addition to silica dust and RCS, the transportation of sand may raise
other concerns among residents of communities near sand mining operations.
New mines are likely to increase truck and rail traffic, and may increase
diesel emissions, noise, road congestion and accidents, and road maintenance
needs. Water resources and reclamation of the site can also be areas of
public interest. Effective communication and cooperative planning between
mining companies and local communities is essential.
What can communities do to protect residents’ health?
By incorporating best practices into the mine’s daily operations on and
off-site, mine operators and communities can work together to create a
mining operation that is economically viable and protective of the health of
workers and the surrounding community. Local agencies have an opportunity to
influence sand mining operations primarily through zoning and direct
negotiation with mine developers to use best management practices
appropriate for the specific location.
For more information:
P-00369 Rev. 10/2012
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Last Revised: October 05, 2012