OSEA Safety News

Crystalline Silica

Wednesday, August 30th, 2017

Crystalline Silica

Crystalline silica is an important industrial material found abundantly in the earth’s crust. Quartz, the most common form of silica, is a component of sand, stone, rock, concrete, brick, block, and mortar. Materials containing quartz are found in a wide variety of workplaces.

Silica dust is hazardous when very small (respirable) particles are inhaled. These respirable dust particles can penetrate deep into the lungs and cause disabling and sometimes fatal lung diseases, including silicosis and lung cancer, as well as kidney disease.

Occupational exposure to respirable crystalline silica occurs when cutting, sawing, drilling, and crushing of concrete, brick, ceramic tiles, rock, and stone products. Occupational exposure also occurs in operations that process or use large quantities of sand, such as foundries and the glass, pottery and concrete products industries. OSHA estimates that more than 2.3 million workers in the United States are potentially exposed to dust containing crystalline silica with nearly 90% of those workers employed in the construction industry.

Industries and operations in which exposure to crystalline silica can occur include, but are not limited to:

  • Construction
  • Glass products
  • Pottery products
  • Structural clay products
  • Concrete products
  • Foundries
  • Dental laboratories
  • Paintings and coatings
  • Jewelry production
  • Refractory products
  • Ready-mix concrete
  • Cut stone and stone products
  • Refractory installation and repair
  • Railroad track maintenance
  • Hydraulic fracturing for gas and oil
  • Abrasive blasting

Health Effects

Occupational exposure to crystalline silica often occurs as part of or working alongside common workplace operations involving cutting, sawing, drilling, and crushing of concrete, brick, block, rock, and stone products. Operations using sand products can also result in worker inhalation of small (respirable) crystalline silica particles in the air. Health effects from silica exposures include:

  • Silicosis, a disabling, non-reversible and sometimes fatal lung disease;
    • Acute silicosis.
    • Chronic silicosis.
  • Other non-malignant respiratory diseases, such as chronic bronchitis and other chronic obstructive pulmonary diseases (COPD).
  • Lung cancer.
  • Kidney disease, including nephritis and end-stage renal disease.

To a lesser extent, there is cause for concern that silica exposures may be associated with auto-immune disorders and cardiovascular disease.

Why do we need new silica standards?

We have known about the dangers of silica for decades. More than 80 years ago, U.S. Secretary of Labor Frances Perkins under President Franklin Roosevelt first brought experts and stakeholders together to determine the best ways to protect workers from silica.

OSHA’s current permissible exposure limits for silica are more than 40 years old. They are based on research from the 1960s and earlier that do not reflect more recent scientific evidence.

Strong evidence shows that the current exposure limits do not adequately protect worker health. For example, since the current exposure limits were adopted, respirable crystalline silica exposure has been found to cause lung cancer and kidney disease at the levels currently permitted.

Many employers are already implementing the necessary measures to protect their workers from silica exposure. The technology for most employers to meet the new standards is widely available and affordable.

Rule requires engineering controls to keep workers from breathing silica dust

The Occupational Safety and Health Administration (OSHA) has issued a final rule to curb lung cancer, silicosis, chronic obstructive pulmonary disease and kidney disease in America's workers by limiting their exposure to respirable crystalline silica. The rule is comprised of two standards, one for Construction and one for General Industry and Maritime.

OSHA estimates that the rule will save over 600 lives and prevent more than 900 new cases of silicosis each year, once its effects are fully realized. The Final Rule is projected to provide net benefits of about $7.7 billion, annually.

About 2.3 million workers are exposed to respirable crystalline silica in their workplaces, including 2 million construction workers who drill, cut, crush, or grind silica-containing materials such as concrete and stone, and 300,000 workers in general industry operations such as brick manufacturing, foundries, and hydraulic fracturing, also known as fracking. Responsible employers have been protecting workers from harmful exposure to respirable crystalline silica for years, using widely-available equipment that controls dust with water or a vacuum system.

Key Provisions

  • Reduces the permissible exposure limit (PEL) for respirable crystalline silica to 50 micrograms per cubic meter of air, averaged over an 8-hour shift. This is expressed as µg/m3.
  • Requires employers to: use engineering controls (such as water or ventilation) to limit worker exposure to the PEL; provide respirators when engineering controls cannot adequately limit exposure; limit worker access to high exposure areas; develop a written exposure control plan, offer medical exams to highly exposed workers, and train workers on silica risks and how to limit exposures.
  • Provides medical exams to monitor highly exposed workers and gives them information about their lung health.
  • Provides flexibility to help employers — especially small businesses — protect workers from silica exposure.

Compliance Schedule

Both standards contained in the final rule take effect on June 23, 2016, after which industries have one to five years to comply with most requirements, based on the following schedule:

  • Construction - September 23, 2017. OSHA delayed enforcement to conduct additional outreach and provide educational materials and guidance for employers
  • General Industry and Maritime - June 23, 2018, two years after the effective date.
  • Hydraulic Fracturing - June 23, 2018, two years after the effective date for all provisions except Engineering Controls, which have a compliance date of June 23, 2021.

What does the standard require for construction companies?

The standard requires employers to limit worker exposures to respirable crystalline silica and to take other steps to protect workers. The standard provides flexible alternatives, especially useful for small employers. Employers can either use a control method laid out in Table 1 of the construction standard, or they can measure workers’ exposure to silica and independently decide which dust controls work best to limit exposures to the PEL in their workplaces.

Regardless of which exposure control method is used, all construction employers covered by the standard are required to:

  • Establish and implement a written exposure control plan that identifies tasks that involve exposure and methods used to protect workers, including procedures to restrict access to work areas where high exposures may occur.
  • Designate a competent person to implement the written exposure control plan.
  • Restrict housekeeping practices that expose workers to silica where feasible alternatives are available.
  • Offer medical exams—including chest X-rays and lung function tests—every three years for workers who are required by the standard to wear a respirator for 30 or more days per year.
  • Train workers on work operations that result in silica exposure and ways to limit exposure.
  • Keep records of workers’ silica exposure and medical exams

What is Table 1?

Table 1 matches common construction tasks with dust control methods, so employers know exactly what they need to do to limit worker exposures to silica. The dust control measures listed in the table include methods known to be effective, like using water to keep dust from getting into the air or using ventilation to capture dust. In some operations, respirators may also be needed.

Employers who follow Table 1 correctly are not required to measure workers’ exposure to silica and are not subject to the PEL.

Table 1 Example: Handheld Power Saws

If workers are sawing silica-containing materials, they can use a saw with a built-in system that continuously applies water to the saw blade. The water limits the amount of respirable crystalline silica that gets into the air. In this example, if a worker uses the saw outdoors for four hours or less per day, no respirator would be needed. If a worker uses the saw for more than four hours per day or any time indoors, they would need to use a respirator with an assigned protection factor (APF) of at least 10. In this case, a NIOSH-certified filtering facepiece respirator that covers the nose and mouth (sometimes referred to as a dust mask) could be used. If a worker needs to use a respirator on 30 or more days a year, they would need to be offered a medical exam.

Alternative exposure control methods

Employers who do not use control methods in 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.

Air sampling is typically performed for the entire operation, and will involve the use of battery powered personal air sampling pumps connected with tubing to a cassette holding a filter that will be analyzed for crystalline silica in accordance with new OSHA standards for industrial hygiene laboratories. The pumps are carefully calibrated to accurately measure the total quantity of air collected.

Editor’s Note: OSEA has industrial hygiene professionals that can assist with workplace measurement of crystalline silica. We also have staff that can provide Crystalline Silica Policy and Procedures, Exposure Control Plans and training to assure compliance to the new standard, scheduled for OSHA enforcement on September 23, 2017.

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