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Controlling Silica Exposure

silicia

Exposure to Silica

Exposure to fine particles of silica has been shown to cause silicosis, a serious and sometimes fatal lung disease. Construction employees who inhale fine particles of silica may be at risk of developing this disease.

Silicosis Symptoms

Silicosis is classified into three types: chronic/classic, accelerated, and acute.

Chronic/classic silicosis, the most common, occurs after 15-20 years of moderate to low exposures to respirable crystalline silica. Symptoms associated with chronic silicosis may or may not be obvious: therefore, workers need to have a chest x-ray to determine if there is lung damage. As the disease progresses, the worker may experience shortness of breath upon exercising and have clinical signs of poor oxygen/carbon dioxide exchange. In the later stages, the worker may experience fatigue, extreme shortness of breath, chest pain, or respiratory failure.

Check out this video on Silicosis and Crystalline Silica.
(Click to play video)

Accelerated silicosis can occur after 5-10 years of high exposures to respirable crystalline silica. Symptoms include severe shortness of breath, weakness, and weight loss. The onset of symptoms takes longer than in acute silicosis.

Acute silicosis occurs after a few months or as long as two years following exposures to extremely high concentrations of respirable crystalline silica. Symptoms of acute silicosis include severe disabling shortness of breath, weakness, and weight loss, which often leads to death.

How Silica is Generated

Silica dust can be generated when materials such as ceramics, concrete, masonry, rock and sand are mixed, blasted, chipped, cut, crushed, drilled, dumped, ground, mixed or driven upon.

Employees at construction sites may be exposed to silica dust during general housekeeping activities such as sweeping, emptying vacuum cleaners and using compressed air for cleaning. Silica exposures may also occur whenever silica-containing dusts are disturbed, such as during material handling. The small particles generated during these activities easily become suspended in the air and, when inhaled, penetrate deep into employees’ lungs.

Visible and Respirable Dust

dust

Visible dust contains large particles that are easy to see. The tiny, respirable-sized particles (those that can get into the deep lung) containing silica pose the greatest hazard and are not visible.

Most dust-generating construction activities produce a mixture of visible and respirable particles.

  • Use visible dust as a general guide for improving dust suppression efforts. If you see visible dust being generated, emissions of respirable silica are probably too high.
  • Measures that control tool-generated dust at the source usually reduce all types of particle emissions, including respirable particles.
  • Do not rely only on visible dust to assess the extent of the silica hazard. There may be airborne respirable dust present that is not visible to the naked eye.

General Rule: If dust containing silica is visible in the air, it’s almost always more than the permissible limit.

Exposure Limits

When employees perform tasks listed in OSHA Standard 1926.1153, Table 1 for more than four hours, they may be required to use respiratory protection. Click on the link above for more specific information.

exposure limits
An employee is monitored for silica dust.

Depending on the degree of exposure, the silica standard for construction requires employers to:

  • 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 8-hour day;
  • Protect workers from respirable crystalline silica exposures above the Permissible Exposure Limit (PEL) of 50 μg/m3, averaged over an 8-hour day;
  • Limit workers' access to areas where they could be exposed above the PEL; and
  • Use dust controls to protect workers from silica exposures above the PEL;

Where exposure exceeds the action level, the employer must assess exposure either through a performance option or monitoring. Where the most recent exposure monitoring indicates that employee exposures are at or above the action level but at or below the PEL, the employer must repeat monitoring within six months.

Collecting an Air Sample

A trained specialist, such as a certified industrial hygienist, will use a device called a cyclone assembly and a sampling pump to trap tiny respirable silica particles from the air in the work environment.

  • The cyclone assembly and sampling pump will be placed on an employee, who will wear the device throughout the work shift for up to 8 hours.
  • All employees may be fitted with the sampling device or just a select few who are closest to the silica source may be fitted. The industrial hygienist can help you determine what will be most appropriate.
  • The hygienist will return at the end of the sampling period to de-activate the sampling pump and remove the filters to be sent for analysis.
exposures

Controlling Exposure

To control exposure to silica dust and fibers, avoid dry sweeping and the use of compressed air on concrete. Both these activities can stir up large amounts of dust. Use a vacuum with high efficiency filters when possible. When these activities cannot be avoided, respirators must be worn.

Best practices to help protect employees against exposures to silica include:

  • Replace crystalline silica materials with safer substitutes, whenever possible.
  • Provide engineering or administrative controls, where feasible, such as local exhaust ventilation and blasting cabinets. Where necessary to reduce exposures below the PEL, use protective equipment or other protective measures.
  • Use all available work practices to control dust exposures, such as water sprays.
  • Wear only a N95 NIOSH-certified respirator, if respirator protection is required. Do not alter the respirator. Do not wear a tight-fitting respirator with a beard or mustache that prevents a good seal between the respirator and the face.

For a more detailed discussion of controlling exposure to respirable silica, see OSHA Stadard 1926.1153, Respirable crystalline silica, and OSHA Publication 3902-07R 2017, Small Entity Compliance Guide for the Respirable Crystalline Silica Standard for Construction.

More Best Practices

best practices
A vacuum hose and an assistant is used to help control exposure to silica.
  • Wear only a Type CE abrasive-blast supplied-air respirator for abrasive blasting.
  • Wear disposable or washable work clothes and shower if facilities are available. Vacuum the dust from your clothes and change into clean clothing before leaving the work site.
  • Participate in training, exposure monitoring, and health screening and surveillance programs to monitor any adverse health effects caused by crystalline silica exposures.
  • Be aware of the operations and the job tasks creating crystalline silica exposures in your workplace environment and know how to protect yourself.
  • Be aware of the health hazards related to exposures to crystalline silica. Smoking adds to the lung damage caused by silica exposures.
  • Do not eat, drink, smoke, or apply cosmetics in areas where crystalline silica dust is present. Wash your hands and face outside of dusty areas before performing any of these activities.
  • Remember: If it's silica, it's not just dust.
IOSH: No Time to Lose Campaign about the consequences of exposure to harmful substances in the workplace.

Training

It’s important for the employer to train all employees who might have exposure to silica while performing demolition operations. Make sure employee training includes:

  • methods and observations to detect the presence of silica
  • when and where the physical and health hazards associated with silica exist
  • steps necessary to eliminate the hazards or at least protect themselves from silica exposure in the workplace

Instructions

Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

Good luck!

1. This dust can be generated when materials such as concrete and masonry, blasted, ground, mixed or driven upon.

2. The employer must ensure that no employee is exposed to a concentration of respirable silica dust in excess of _____.

3. To control exposure to silica dust and fibers during demolition, _____.

4. If respiratory protection is required during demolition, wear only a _____.

5. What should demolition workers who have been exposed to silica fibers and dust do before leaving the work site?


Have a great day!

Important! You will receive an "error" message unless all questions are answered.