Crystalline Silica Exposure (Article written by GVS Filter Technology. Posted by Bill Stephens
Each day more than two million workers are exposed to respirable crystalline silica. When crystalline silica particles are inhaled, they can cause irreversible health problems which include silicosis, lung cancer, chronic obstructive pulmonary disease (COPD) and kidney disease.
Silica is benign in its undisturbed state but becomes a health hazard when the solid crystals are reduced to tiny dust particles that can be easily inhaled. Whenever materials containing crystalline silica — masonry, brick, stone, concrete, glass — are sawn, drilled, chipped or crushed, silica dust is created and released.
In 1971, the Occupational Safety and Health Administration (OSHA) recognized respirable crystalline silica as a health hazard and established a permissible exposure limit (PEL) for it. The PEL was based on studies conducted in the 1960s. Technology advancements and demands for safer work conditions prompted OSHA to update their silica exposure rule to reflect these changes. OSHA published an updated final rule in March 2016. The rule requires employers to monitor their workplace to determine if workers are exposed to respirable crystalline silica and create a workplace exposure plan that outlines the procedures and controls that will be taken to prevent unsafe levels of exposure.
To improve worker protection, OSHA’s final rule to protect workers from exposure to crystalline silica will be done in two new crystalline silica standards: one for general industry and maritime (Industries have to comply by June 23, 2018), and for construction (Industry must comply by September 23, 2017). Even though the timeline has been adjusted, if you are in the construction industry you should be changing the way you work now.
The New OSHA Standard
- OSHA now reduces the permissible exposure limit (PEL) for respirable crystalline silica to 50 micrograms per cubic meter of air, averaged over an 8 hour shift which is several times lower than the previous PEL. In practical terms, this means if you can see airborne dust, the concentrations are likely exceeding the new PEL.
- Requires employers to use: –Engineering controls (such as water or ventilation) to limit worker exposure to respirable silica dust to the PEL –
- Provide respirators when engineering controls are not available or existing engineering controls cannot adequately limit exposure
- Limit worker access to high exposure areas –Develop a written exposure control plan
- Train workers on silica risks and how to limit exposures
- Provide medical exams to monitor highly exposed workers and gives them information about their lung health
- Establish and implement a written exposure control plan to identify tasks that involve exposure and methods used to protect workers, including procedures to restrict access to work areas where high exposures may occur.
- Also, employers need to designate a competent person to implement the written exposure control plan.
Workers in many industries can be exposed to respirable crystalline silica in the form of sand or when materials containing crystalline silica are ground, cut, milled or otherwise handled in a manner that causes silica dust to become airborne, including:
Structural clay products
Paintings and coatings
Cut stone and stone products
Abrasive blasting in maritime, construction, and general industry
Refractory furnace installation and repair
Oil and gas operations
Potential for Exposure During Construction
Concrete and masonry products contain silica sand and rock containing silica. Since these products are primary materials for construction, construction workers may be easily exposed to respirable crystalline silica during activities such as the following:
- Chipping, hammering, and drilling of rock
- Crushing, loading, hauling, and dumping of rock
- Abrasive blasting using silica sand as the abrasive
- Abrasive blasting of concrete (regardless of abrasive used)
- Sawing, hammering, drilling, grinding, and chipping of concrete or masonry
- Demolition of concrete and masonry structures
- Dry sweeping or pressurized air blowing of concrete, rock, or sand dust
Even materials containing small amounts of crystalline silica may be hazardous if they are used in ways that produce high dust concentrations.
What type of respirator meets the OSHA requirement?
Crystalline Silica exposure depends on the concentration of the particulate. Exposure can occur during common construction tasks such as using masonry saws, grinders, drills, jackhammers and handheld powered chipping tools; operating vehicle-mounted drilling rigs; milling; operating crushing machines; and using heavy equipment for demolition or certain other tasks. Without dust controls, using a handheld power saw to cut concrete can expose workers to high levels of respirable crystalline silica. The construction standard does not apply where exposures will remain low under any foreseeable conditions; for example, when only performing tasks such as mixing mortar; pouring concrete footers, slab foundation and foundation walls; and removing concrete formwork.
Table 1 Example:
Handheld Power Saws If workers are sawing silica-containing materials, they can use a saw with a built-in system that applies water to the saw blade. The water limits the amount of respirable crystalline silica that gets into the air.
* (APF = 10) Any particulate respirator equipped with an N95, R95, or P95 filter (including N95, R95, and P95 filtering facepieces) except quarter-mask respirators. The following filters may also be used: N99, R99, P99, N100, R100, P100.
Employers who do not use control methods on Table 1 must:
• Measure the amount of silica that workers are exposed to if it may be at or above an action level of 25 μg/m3 (micrograms of silica per cubic meter of air), averaged over an eight hour day.
• Protect workers from respirable crystalline silica exposures above the permissible exposure limit of 50 μg/m3, averaged over an eight-hour day.
• Use dust controls to protect workers from silica exposures above the PEL.
• Provide respirators to workers when dust controls cannot limit exposures to the PEL