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Course 851 - Silica Dust Safety in Construction

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Exposure to Silica Dust

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Exposure to fine particles of silica while cutting, drilling, and blasting 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. The small particles easily become suspended in the air and, when inhaled, penetrate deep into employees’ lungs.

Although the primary effect of overexposure to silica dust is silicosis, let’s not forget employees may also suffer from lung, stomach and other cancers, tuberculosis, chronic obstructive pulmonary disorder, immune system effects, and kidney effects. The only way to prevent disease is to eliminate exposure to crystalline silica or reduce crystalline silica exposure to safe levels.

Silicosis

Silicosis: A Preventable Disease
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Silicosis is one of the world’s oldest known occupational diseases; reports of employees with the disease date back to ancient Greece. By 1800, many common names for the lung disease, such as “masons’ disease” were given to silicosis. Despite its different names through the centuries, silicosis is a single disease with a single cause–exposure to respirable crystalline silica dust.

There are three types of silicosis, depending upon the airborne concentration of crystalline silica to which a worker has been exposed:

  1. Chronic/classic silicosis, the most common form of the disease, 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.
  2. 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.
  3. 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.

Symptoms of Exposure

Chronic silicosis may go undetected for years in the early stages; in fact, a chest X-ray may not reveal an abnormality until after 15 or 20 years of exposure. The body's ability to fight infections may be overwhelmed by silica dust in the lungs, making workers more susceptible to certain illnesses, such as tuberculosis. As silicosis progresses, you may exhibit one or more of the following symptoms:

  • shortness of breath following physical exertion
  • severe cough
  • fatigue
  • loss of appetite
  • chest pains
  • fever

If You Are Exposed

If you believe you are overexposed to silica dust, visit a doctor who knows about lung diseases. A medical examination that includes a complete work history, a chest X-ray, and lung function test is the only sure way to determine if you have silicosis. The National Institute of Occupational Safety and Health (NIOSH) recommends medical examinations occur before job placement or upon entering a trade, and at least every 3 years thereafter.

Measuring Airborne Silica

If it is known or suspected silica is being used and it may be in the air, the next step is to determine how much is there. To do that, sample the air during the work being conducted.

Collecting an Air Sample: A trained specialist, such as a certified industrial hygienist, will use a combination 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.

Laboratory Analysis: After collecting the air sample, the next task is to select a competent laboratory that does quality analysis work. This is critical to determining compliance with the OSHA crystalline silica standard. The work in monitoring exposure is wasted if samples are mishandled or analyzed incorrectly.

Comparing Exposure Results to OSHA’s Limit

It is important to know there is not one crystalline silica exposure limit for all cases. Rather, the limit is derived from a calculation that takes into account the percentage of quartz, cristobalite, tridymite, and respirable dust specific to your particular worksite.

OSHA regulation 29 CFR 1910.1000 Table Z-3 is used to determine the exposure limits for crystalline silica. Though this regulation is under the General Industry Standard, crystalline silica exposures in the Construction and Maritime Industries are subject to this same limit. Regulating these industries under the General Industry Standard is specifically addressed in Appendix E of the OSHA Special Emphasis Program (SEP) for Silicosis.

If you are a math whiz, you can calculate the degree of exposure which employees are exposed by following the instructions on OSHA’s “Determining Exposure Limits for Silica” webpage.

However, we recommend using OSHA’s “Advisor Genius” to compare silica levels to the OSHA Limit. The Genius performs calculations for a respirable dust sample. Note: The Advisor Genius has been written using JavaScript. If your software does not support this, the Genius will not operate properly.

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. What serious disease is caused by exposure to fine particles of silica?

2. Which of the following occurs after 15-20 years of moderate to low exposures to respirable crystalline silica?

3. What is the only sure way to determine if you have silicosis?

4. What is the measurement OSHA uses to regulate silica dust exposure during a full workshift?

5. What is the procedure to determine how much silica dust is present?


Have a great day!

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