What is crystalline silica?
Crystalline silica is a basic component of soil, sand, granite, and many other minerals. Quartz is the most common form of crystalline silica. Concrete contains a significant amount of silica also. It is respirable when workers chip, cut, drill, or grind objects that contain crystalline silica.
What are the hazards of crystalline silica?
Silica exposure remains a serious threat to nearly 2 million U.S. workers, including more than 100,000 workers in high risk jobs such as abrasive blasting, foundry work, stonecutting, rock drilling, quarry work, tunneling and construction.
Crystalline silica has been classified as a human lung carcinogen.
Additionally, breathing crystalline silica dust can cause silicosis,
which in severe cases can be disabling, or even fatal. The respirable silica dust
enters the lungs and causes the formation of scar tissues, thus reducing the lungs’
ability to take in oxygen. There is no cure for silicosis.
infections like tuberculosis. In addition, smoking causes lung damage and adds to
the damage caused by breathing silica dust.
What are the symptoms of silicosis?
There are several stages of silicosis. Early stages may go completely unnoticed. Continued exposure may result in the exposed person noticing a shortness of breath upon exercising, possible fever and occasionally bluish skin at the ear lobes or lips. Silicosis makes a person more susceptible to infectious diseases of the lungs like tuberculosis. Progression of the disease leads to fatigue, extreme shortness of breath, loss of appetite, pain in the chest, and respiratory failure, which all may lead eventually to death.
Three types of silicosis:
Chronic silicosis which usually occurs after ten or more years of exposure to crystalline silica at relatively low concentrations.
Accelerated silicosis which results from exposure to high concentrations of crystalline silica and develops five to ten years after the initial exposure.
Acute silicosis which occurs where exposure concentrations are the highest and can cause symptoms to develop within a few weeks to four or five years after the initial exposure.
Where are construction workers exposed to crystalline silica?
Exposure occurs during many different construction activities. The most severe exposures have occurred during abrasive blasting with sand to remove paint and rust from bridges, tanks, concrete structures, and other surfaces. Other construction activities that may result in severe exposure include: jack hammering, rock/well drilling, concrete missing, concrete drilling, brick and concrete block cutting and sawing, tuck pointing, tunneling operations.
The following are high-risk tasks for silica exposure:
1. Crushing, loading, hauling, chipping, hammering, drilling, and dumping of rock or concrete
2. Chipping, hammering, drilling, sawing, and grinding concrete or masonry
3. Removal of paint and rust with power tools
4. Abrasive blasting of bridges, pipes, tanks, and other painted surfaces especially while using silica sand
5. Grinding mortar
6. Abrasive blasting of concrete
7. Demolition of concrete and masonry structures
8. Dry sweeping or pressurized air-blowing of concrete or dust
9. Jack hammering on various materials
Workers in the following occupations are at risk for developing silicosis:
- Highway and bridge construction and repair
- Building construction, demolition, and repair
- Abrasive blasting
- Masonry work
- Concrete finishing
- Drywall finishing
- Rock drilling
- Mining
- Sand and gravel screening
- Rock crushing (for road base)
What is the liklihood of silica overexposure on constructionworksites?
The results of studies of airborne silica on construction worksites vary. Most studies however, suggest that over-exposure occurs on more than 50% of worksites. The rule-of-thumb for silica exposure is; “if dust containing silica is visible in the air, it is almost always over the permissible limit.”
How is OSHA addressing exposure to crystalline silica?
OSHA has an established Permissible Exposure Limit, or PEL, which is the maximum amount of crystalline silica to which workers may be exposed during an 8-hour shift (29 CFR 1926.55, 1910.1000). OSHA also requires hazard communication training for workers exposed to crystalline silica, and requires a respirator program until engineering controls are implemented.
Additionally, OSHA has a National Emphasis Program (NEP) for Crystalline Silica exposure to identify, reduce, and eliminate health hazards associated with occupational
What does OSHA require if overexposure to silica exists?
Employers are required to provide and assure the use of appropriate controls or crystalline silica-containing dust.
Required by existing OSHA standards:
1. Training and information to workers on crystalline silica (MSDS)
2. Ongoing personal air monitoring program
3. Availability of air and medical surveillance data to workers
4. Respiratory protection program
a) Written program
b) Training documentation
c) Fit testing documentation (including dust masks)
d) Medical clearance documentation
5. Housekeeping program
6. Construction safety and health program
Recommended by OSHA:
1. Dust control program
2. Medical surveillance program/disease reporting
3. Equipment maintenance program
4. Isolated personal hygiene facilities, eating facilities, and a clothing change area
5. Record keeping
6. Regulated areas/warning signs
What are some recommendations to limit exposures to silica?
There are various recommendations to reduce exposures to respirable crystalline silica on the jobsite. The most efficient method is to perform a silica exposure evaluation and control plan. You or your safety specialist can incorporate a plan utilizing your location, manpower and other resources to control the silica and be cost effective.
Workers can limit their exposure by being aware of and practicing the following:
· Use materials that do not contain silica when possible.
· Recognize where silica dust may be generated and plan ahead to eliminate or control the dust at the source.
· Use controls such as blast-cleaning machines and cabinets, wet drilling, or wet sawing of silica-containing materials, to control the hazard and protect adjacent workers from exposure.
· Routinely maintain dust control systems to keep them in good working order.
· Conduct air monitoring to measure worker exposure and ensure that controls are providing adequate protection for workers.
· Use adequate respiratory protection when source controls cannot keep silica exposures below the PEL.
· Post warning signs to mark the boundaries of work areas contaminated with respirable crystalline silica.
· Provide workers with training that includes information about health effects, work practices, and protective equipment for respirable crystalline silica.
· Use a respirator approved for protection against crystalline silica-containing dust (e.g. CE positive pressure abrasive blasting respirator for sandblasting).
· Change into disposable or washable work clothes at the jobsite; shower (where available) and change into clean clothing before leaving the jobsite to prevent contamination of cars, homes, and other areas.
· Do not eat, drink, use tobacco products, or apply cosmetics in areas where there is dust containing crystalline silica.
· Wash your hands and face before eating, drinking, smoking, or applying cosmetics in areas where there is dust containing crystalline silica.
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