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People who work in mining may breathe in tiny bits of silica, and eventually, develop a serious lung disease called silicosis. There is no cure for silicosis. Lung damage from silicosis is permanent, but with proper precautions it is preventable. Silicosis usually develops after years of exposure to low levels of silica. However, it can develop much sooner (even within a few weeks) if you breathe in high levels of silica dust. Breathing in silica dust is also associated with lung cancer, tuberculosis, and airway diseases.
Silica is the common name for silicon dioxide, a white or colorless compound found naturally in sand, granite, and many other types of rock. Quartz is the most common form of silica and is the second most common mineral in the earth’s surface. Since it is so abundant, quartz is present in nearly all mining operations.
Miners working at surface mines are at risk of being exposed to silica-containing dust. The most common mine activities where exposure may be elevated include the drilling of rock, crushing, and loading of mine material. Miners operating equipment such a highway drills, end loaders, dozers and trucks on mine property have a high probability of exposure. Furthermore, all miners working at surface coal mines are at risk of being exposed to silica-containing dust.
Symptoms of silicosis may not appear in the early stages, but can develop with time and usually get worse as the disease progresses. Symptoms may include:
- Shortness of breath/difficulty breathing
- Severe cough and chest pain
- Weakness/fatigue
Miners must undergo a medical examination to determine the presence of silicosis. This is especially important for miners who have worked in areas with a high probability of exposure to silica-containing dust. Talk to your doctor about your silica exposure and the necessary medical screening.
Scope
The Mine Safety and Health Administration (MSHA) regulations require that controls be used when drilling rock to prevent miners from being exposed to dust from the drilling action. Holes must be drilled wet or other effective means must be used to prevent dust exposures. Use of dry dust collectors on drills is an example of an effective means of control.
Respirable coal mine dust: MSHA continues to enforce the 2.0 mg/m3 or lower standard for respirable coal mine dust. Samples are analyzed for silica content to determine if the respirable dust standard should be reduced to control the miner's exposure to silica.
Silica dust: Each operator shall continuously maintain the average concentration of respirable quartz dust in the mine atmosphere during each shift to which each miner in the active workings of each mine is exposed at or below 0.1 mg/m3 (100 micrograms per cubic meter or µg/m3) as measured with an approved sampling device and expressed in terms of an equivalent concentration.
When the equivalent concentration of respirable quartz dust exceeds 100 µg/m3, the operator shall continuously maintain the average concentration of respirable dust in the mine atmosphere during each shift to which each miner in the active workings is exposed as measured with an approved sampling device and expressed in terms of an equivalent concentration at or below the applicable standard. The applicable standard is computed by dividing the percent of quartz into the number 10. The application of this formula shall not result in the applicable standard that exceeds the 2.0 mg/m3 or lower standard for respirable coal mine dust.
Regulatory citations
- 30 CFR 58.610 — Abrasive blasting
- 30 CFR Part 71 — Mandatory health standards—surface coal mines and surface work areas of underground coal mines
Key definitions
- Certified person:. An individual certified by the Secretary in accordance with 71.202 to take respirable dust samples required by this part or certified in accordance with 71.203 to perform maintenance and calibration of respirable dust sampling equipment as required by this part.
- Coal mine dust personal sampler unit (CMDPSU): A personal sampling device approved under 30 CFR 74 Subpart B.
- Concentration: A measure of the amount of a substance contained per unit volume of air.
- Continuous personal dust monitor (CPDM): A personal sampling device approved under 30 CFR 74 Subpart C.
- Designated work position (DWP): A work position in a surface coal mine and surface work area of an underground coal mine designated for sampling to measure respirable dust generation sources in the active workings. Each DWP will be assigned a four-digit number assigned by MSHA identifying the specific physical portion of the mine that is affected, followed by a three-digit MSHA coal mining occupation code describing the location to which a miner is assigned in the performance of his or her regular duties.
- Equivalent concentration: The concentration of respirable coal mine dust, including quartz, expressed in milligrams per cubic meter of air (mg/m3) as measured with an approved sampling device, determined by dividing the weight of dust in milligrams collected on the filter of an approved sampling device by the volume of air in cubic meters passing through the filter (sampling time in minutes (t) times the sampling airflow rate in cubic meters per minute), and then converting that concentration to an equivalent concentration as measured by the Mining Research Establishment (MRE) instrument. When the approved sampling device is:
- The CMDPSU, the equivalent concentration is determined by multiplying the concentration of respirable coal mine dust by the constant factor prescribed by the Secretary.
- The CPDM, the device shall be programmed to automatically report end-of-shift concentration measurements as equivalent concentrations.
- Representative sample: A respirable dust sample, expressed as an equivalent concentration, that reflects typical dust concentration levels in the working environment of the DWP when performing normal duties.
Summary of requirements
Mine operators are required to provide and assure the use of appropriate controls for dust while drilling in rock.
Miners should:
- Use all available engineering controls such as dust collectors, wet drilling, drill platform skirts, and enclosed cabs.
- Use respirators to help maximize protection, especially when working in dust for short periods. When using a respirator, it is essential that it is appropriately maintained, equipped with new filters when necessary, properly fitted, and approved for use in silica-containing dust. In addition, to ensure a tight facial seal, you cannot have a beard or mustache.
- Change into clean clothes before leaving your worksite, and wash hands and face frequently.
- Talk to your supervisor or Mine Safety and Health Administration representative if you notice any unsafe working conditions.