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 operations using sand products, including glass manufacturing and sandblasting.

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 tissue, thus reducing the lungs’ ability to take in oxygen. There is no cure for silicosis.

This training session will cover the hazards of respirable crystalline silica and how to protect yourself and others each day on the job.

Session Objectives

By the end if this course you will be able to:

• Identify the health hazards associated with exposure to silica dust;
• Recognize job tasks that could lead to exposure to silica dust;
• Access the respirable crystalline silica rule for general industry;
• Read labels, safety data sheets, or SDSs, and signs at the entrances to regulated areas that communicate silica dust hazards;
• Apply silica dust exposure control methods; and
• Describe the medical surveillance program.

Knowledge Check 1

Before we begin the session, let’s take a few minutes to see how much you already know about silicosis.

– True or False? Since silicosis affects lung function, it makes someone more susceptible to lung infections like tuberculosis.

• The correct answer is True.

– Acute silicosis is a type of silicosis that can occur after how long following exposure to extremely high concentrations of respirable silica dust?

After a few months to up to 2 years following exposure

After 3 years following exposure

After 5 to 10 years following exposure

After 20 years following exposure

The correct answer is:

• After a few months to up to 2 years following exposure.

– True or False? Workers can be exposed to silica dust in the electronics industry.

• The correct answer is True.

What Is Respirable Crystalline Silica?

Crystalline silica is a basic component of soil. You’ll find silica in a lot of places.

• The most common form of silica is quartz, a component of stone; concrete; sand; and brick. Simply put, silica is everywhere.
• If you’ve touched a rock or been to the beach, you’ve handled silica. But don’t worry; it’s not harmful as sand or rocks or even bricks. Materials that contain crystalline silica are not hazardous unless they are broken into very small-sized particles, typically 100 times smaller than ordinary sand and not visible to the naked eye, that can get in your lungs—this is called “respirable crystalline silica.” Silica is found in common workplace operations involving sand products.

The hazards of exposure to silica dust have been known for thousands of years. Respiratory problems from breathing silica dust date back to the Greeks and Romans.

• But with the invention of powerful stone-cutting tools in the 19th and 20th centuries there was an increase in workers developing silicosis and other lung ailments. The U.S. Department of Labor first highlighted the hazards of respirable crystalline silica in the 1930s, after a wave of worker deaths. But it’s not just silicosis that we need to worry about. Inhaling crystalline silica dust can lead to other serious disorders, including;
• Tuberculosis;
• Chronic obstructive pulmonary disease—or COPD;
• Kidney disease, where studies of workers exposed to respirable crystalline silica show increased risk of developing it. Kidney failure has been observed among workers with high silica exposure who also were suffering from silicosis.
• Also, immunological disorders like systemic lupus and scleroderma have been linked to silica exposure.

Cancers

Other serious and often fatal conditions linked to exposure to silica dust include:

• Lung cancer;
• Stomach cancer; and
• Esophageal cancer.
• The International Agency for Research on Cancer, or IARC, and the U.S. National Toxicology Program have designated crystalline silica as a group one carcinogenic (substance that causes cancer) to humans.
• This warning needs to be included on the SDSs of silica-containing products.

Silicosis

Many workers don’t think they need protection from silica dust, but exposure to silica dust is hazardous.

• The most common illness from exposure is silicosis, which is a fibrotic disease of the lungs.
• It is caused by breathing silica dust into your lungs. The dust enters the lungs, but you cannot exhale it.
• It forms scar tissue that makes it difficult to take in oxygen.
• And there is no cure for silicosis. There are three types of silicosis, depending on the level and time of exposure.
• They are chronic, accelerated, and acute silicosis, which we’ll discuss in the following slides.

Chronic Silicosis

Chronic or simple silicosis is the most common form of silicosis.

• Chronic silicosis typically occurs from long-term exposure—15 to 20 years—to low amounts of silica dust;
• It causes shortness of breath and hinders the body’s ability to fight infection because of damage to the lungs; and
• Silicosis makes the person susceptible to other lung illnesses, like tuberculosis.

Accelerated Silicosis

• Accelerated silicosis can occur after 5 to 10 years of high exposures to respirable silica dust.
• The symptoms include severe shortness of breath, weakness, and weight loss.

Acute Silicosis

• Acute silicosis occurs after a few months or as long as 2 years following exposure to extremely high concentrations of respirable silica.
• Symptoms of acute silicosis include severe disabling shortness of breath, weakness, and weight loss, which often leads to death.

High-Risk Operations: Abrasive Blasting/Sanding

There are a number of high-risk operations in general industry that increase your risk of exposure to silica dust. Let’s start with discussing abrasive blasting.

• Abrasive blasting—or sandblasting—uses compressed air or water to direct a high-velocity stream of an abrasive material—like sand.
• Abrasive is used to clean an object or surface, remove burrs, apply a texture, or prepare a surface for the application of paint or other type of coating.
• Abrasive blasting operations can create high levels of silica dust and noise.

High-Risk Operations: Sand Casting Foundries

Sand casting is selected as a preferred method to produce shaped parts from less than a pound, to very large parts.

• The process is very versatile and cost-effective.
• Sand casting foundries are among the workplaces most likely for workers to be exposed to silica dust.

High-Risk Operations: Glass Manufacturing

The manufacture of glass involves numerous hazards.

• A handful of chemicals and a large amount of crystalline silica constitute most of the ingredients.
• Dust from these substances is often very fine and can easily become airborne.

High-Risk Operations: Stone Cutting and Manufacturing

Workers who manufacture stone are at risk of significant silica exposure.

• Production operators (such as sawyers), inspectors (including quality control technicians), and staff who perform maintenance and housekeeping activities in manufacturing facilities may be exposed to hazardous levels of airborne silica dust.

High-Risk Operations: Oil and Gas Industry

Silica exposure is also a concern in oil-and-natural gas exploration industries.

• Sands that are used in hydraulic fracturing (“fracking”) can present an exposure hazard. Silica sand is used to open the fractures created by fracking and horizontal drilling technologies. • Workers who are responsible for refining or transporting silica sand are especially at risk for breathing dust into their lungs.

Knowledge Check 2

We’ve gone over a lot of information so far—let’s pause to see how well you are remembering what you’ve learned.

These questions are not graded. They are just to help you remember the important information we’ve been over so far.

– True or False? Silica is not harmful in rock form or as sand at the beach, but it is harmful in brick form.

• The correct answer is False.

If you’ve touched a rock or been to the beach, you’ve handled silica. But don’t worry; it’s not harmful as sand, rock, or brick. Materials that contain crystalline silica are not hazardous unless they are broken into very small-sized particles that can get in your lungs—this is called “respirable crystalline silica.”

– In addition to the debilitating disease known as silicosis, what other conditions have been linked to exposure to silica dust? (Select all that apply.)

Bladder stones

Tuberculosis

Kidney disease

OCD

COPD

• The answer is all of these except for bladder stones. Inhaling crystalline silica dust can lead to other serious, sometimes fatal illnesses, including tuberculosis; kidney disease; chronic obstructive pulmonary disease—or COPD. Lung cancer and other cancers have also been linked to silica exposure.

– There are three types of silicosis. Which type is the most common and typically occurs after 15 to 20 years following low to moderate exposure to respirable silica dust?

-Acute silicosis

-Accelerated silicosis

-Chronic silicosis

• The correct answer is chronic silicosis. It is the most common form of silicosis and typically occurs after 15 to 20 years of low to moderate exposure.

– True or False? Production operators (such as sawyers), inspectors (including quality control technicians), and staff who perform maintenance and housekeeping activities in stone cutting and manufacturing facilities all may be exposed to hazardous levels of airborne silica dust.

• The correct answer is True.

Production operators, inspectors, and staff who perform maintenance and housekeeping activities in manufacturing facilities may be exposed to hazardous levels of airborne silica dust. Those workers who manufacture stone are at risk of significant silica exposure.

Worker’s Right to Know

The federal hazard communication, or worker right-to-know, rule says you have a right to know about the potential health and physical hazards of silica and silica-containing materials through signage, information, product labels, and SDSs.

• The labels should identify the type of hazard associated with the material—they include pictograms that provide a quick reference to the potential health hazards of the product.
• The safety data sheet provides a more detailed explanation of the hazards and measures to take to protect yourself, including required personal protective equipment, or PPE.

Labels

Generally, all containers of silica-containing products must be labeled with the required information. This includes:

• The product identifier; and
• A combination of words, pictures, or symbols that provide general information about the hazards of the material; and
• Specific information regarding the potential health hazards.

Safety Data Sheets

Labels give you a snapshot of the risks associated with a product. The SDS gives you the most complete and detailed information. The SDS for each chemical:

• Is a detailed written description of the chemical;
• Describes its hazards, as well as precautions and remedies to releases and exposure; and
• Must be readily available for you to read.
• You should always read the SDS before starting to work with a silica-containing material.

Respirable Crystalline Silica Rule

• The Occupational Safety and Health Administration’s, or OSHA’s, respirable crystalline silica rule establishes a permissible exposure limit, or PEL, for silica, which is 50 micrograms per cubic meter of air as an 8-hour time-weighted average, or TWA.
• Regardless of the PEL, if you work in an occupation or in work areas where silica-containing materials are manufactured, used, drilled, polished, sanded, chipped, sawed, crushed, or otherwise worked on in a way that can generate dust, it is very likely silica is in the air. There may be silica particles in the air even though you don’t see any dust. Dust particles that get in your lungs are typically 100 times smaller than a grain of sand.
• The rule requires this training so you will recognize the hazards and minimize your risk of exposure to airborne silica.

Respirable Crystalline Silica Rule

Where there are jobs that involve the possible release of silica dust into the air, employers are required to:

• Monitor the air;
• Implement engineering and work practice controls;
• Select the proper respiratory protection, if needed, to protect you; and
• Implement a medical surveillance program for workers exposed to silica dust at certain levels for 30 or more days per year. Your supervisor has copies of the rule available to you.

Regulated Areas

Regulated areas are areas in your workplace where exposures to silica dust are, or can reasonably be expected to be, above the PEL.

• Regulated areas are marked off from the rest of the workplace to prevent you or others from being exposed. Boundaries can be marked off with cones, tape, barricades, lines, or other methods.
• There must also be a sign posted at each entrance to the regulated area that reads:

DANGER

RESPIRABLE CRYSTALLINE SILICA

MAY CAUSE CANCER

CAUSES DAMAGE TO LUNGS

WEAR RESPIRATORY PROTECTION IN THIS AREA

AUTHORIZED PERSONNEL ONLY

Besides keeping other workers away from the area, the signs also let workers who are entering the area know the hazards of the area and that they need respiratory protection.

• An appropriate respirator is required at all times for everyone inside a regulated area.

Controlling Exposure: Engineering Controls

Before you begin a job, make sure sources of exposure have been identified and the most effective methods to control your exposure above the PEL have been selected.

Engineering and work practice controls are the first line of defense in protecting you from exposure to silica dust.

Engineering controls involve a mechanical or other kind of process integrated with the worker’s tools or equipment to eliminate exposure and could include:

• Local exhaust ventilation at or near the point where the dust is created, such as an exhaust hood;
• High-efficiency particulate air, or HEPA, vacuums attached to the work tool or equipment;
• Water or foam suppression systems integrated with tools and equipment like grinders, chippers, drills, cutters, and saws, such as a concrete saw housing with a hose assembly that directs water to the blade; and
• Isolation, which separates employees from the dust source by containing the dust or isolating employees―for example, a ventilated control booth.

Controlling Exposure: Work Practice Controls

Work practice controls involve performing a task in a way that reduces the chance or levels of exposure. Work practice controls are often used along with engineering controls and often enhance them. Some work practice controls include:

• Spraying a mist of water over silica dust before sweeping it up;
• Inspecting and maintaining engineering controls to fix malfunctions that could cause increased exposures;
• Scheduling a work task that involves high levels of exposure to dust when no other workers are in the area; and
• Keeping windows closed near the local exhaust ventilation source, which is an example of using a work practice to maximize the effect of an engineering control.

Any change or increase in visible silica dust is an indication that engineering and/or work practice controls may not be working properly, so watch for changes in dust emissions, and make adjustments or repairs to control measures accordingly.

Controlling Exposure: Respiratory Controls

In addition to wearing respirators in regulated areas, respirators must be used:

• When the engineering and work practice controls cannot control the silica dust exposure at levels below the PEL;
• When installing or implementing engineering and work practice controls while exposed to airborne silica above the PEL; and
• When engineering and work practice controls can’t be used during some maintenance and repair work;
• But respirators must not be used as a first line of defense against exposure when effective engineering and work practice controls are in place.

Any change or increase in visible dust indicates that engineering and work practice controls may not be working properly. Respirators can protect you against exposure until the controls are adjusted or repaired to work properly.

Controlling Exposure: Respirator Use

As we just discussed, when the silica dust can’t be controlled sufficiently, you need to use a respirator.

• When respirators are used, follow the respiratory protection program at the worksite.
• Follow your training when wearing and using the respirator; otherwise, you may think your respirator is providing protection when it is not.
• Make sure your respirator fits properly to prevent leaks around the edges. Fit-test it before the first time you wear it.
• You can’t have a beard with a respirator. You can’t get a proper fit with a beard—the respirator will leak. The only exception to the no-beard rule is when a sandblasting hood is used, since it covers the whole head.

Controlling Exposure: Housekeeping

There are also housekeeping or cleaning methods to avoid in order to reduce or prevent exposure to silica dust, unless there are no workable or safer alternatives for the task at hand.

• To reduce the possibility of silica dust going airborne, avoid dry sweeping; and
• Do not use compressed air when cleaning up or preparing a work area, unless the compressed air or dry sweeping is used together with a ventilation system to capture the dust. Both of these activities just stir up large amounts of dust into the air— and that’s the danger!
• Instead, use a wet sweeping method; or
• Use a vacuum with HEPA filters whenever possible.

Sand Delivery & Batch Operations: Engineering Controls

Let’s use a job task example to explain engineering controls. Where the task is the handling of sand during delivery and in batch operations, examples of engineering controls your employer could implement include:

• Pneumatic conveyor systems that are enclosed and maintained at negative pressure; or
• Water is automatically misted onto the sand before it is mixed in batch operations.

Sand Delivery & Batch Operations: Work Practice Controls

Examples of work practice controls for handling of sand during delivery and in batch operations could include:

• Checking that connections between rail cars or trucks and storage silos are effectively sealed before transferring sand;
• Applying water mist manually to sand before batch operations;
• Checking to make sure sand is not released from any point of the pneumatic transfer system;
• Having a supervisor or engineer inspect the system if sand is being released;
• Inspecting weekly enclosures and seals on the pneumatic transfer system for damage; and
• Measuring daily the pressure in the pneumatic system.

Sand Delivery & Batch Operations: Housekeeping Measures

Examples of housekeeping measures for the tasks we just discussed could include:

• Using the central vacuum system for cleaning;
• Using a HEPA-filtered vacuum for cleaning spills; and
• Prohibiting dry sweeping.

Personal Hygiene

Another step to take to reduce your risk of exposure to harmful silica dust is following good hygiene practices. For example:

• Use disposable clothes while you’re working on tasks involving silica dust. Or, if you don’t have disposables at your worksite, keep a set of washable work clothes at the site.
• And before removing your work clothes after your shift, vacuum them very carefully to safely remove silica particles.
• Then take a shower to remove any contaminants from your skin before putting on your street clothes.
• Of course, if you’ve been working in an area where there is silica dust, be sure to wash your hands before eating, drinking, or smoking. Do not bring food, beverages, or cigarettes into an area that has silica dust.

Medical Surveillance

Your employer is required to make medical surveillance screenings available to you to identify any silica exposure-related health effects.

• It needs to be made available to you if you are exposed to silica dust at or above the action level of 25 micrograms per cubic meter of air (μg/m3 ) as an 8-hour TWA for 30 or more days per year.
• This means you need to go to the doctor—or other qualified health professional—have an exam and get a written medical opinion. The opinion will include:

– The date of the exam;

– A statement that the exam specifically checked for silica exposure; and

– Any recommended limitations on your exposure to silica based on the doctor’s findings.

• Any other information learned from the exam is private, and it does not need to be shared with your employer.

What Will the Exam Involve?

OSHA specifies that your doctor’s exam must include:

• A review of your medical and work history;
• A physical examination with special emphasis on the respiratory system;
• A chest X-ray;
• A pulmonary function test;
• A test for latent tuberculosis; and
• Any other tests that your doctor deems appropriate.

Knowledge Check 3

Now we’ve come to the end of this session on Silica Dust in General Industry—Preventing Exposure, so it’s time to see how much you’ve learned.

– True or False? The respirable crystalline silica rule establishes a PEL for silica of 100 micrograms per cubic meter of air as an 8-hour time-weighted average.

• The correct answer is False. The respirable crystalline silica rule establishes a PEL for silica of 50 micrograms per cubic meter of air as an 8-hour TWA.

– Your employer is required to make medical surveillance screenings available to you to identify any silica exposure-related health effects if you are exposed to silica dust at or above the action level as an 8-hour TWA for 30 or more days per year. What is the action level?

25 micrograms per cubic meter of air

50 micrograms per cubic meter of air

100 micrograms per cubic meter of air

250 micrograms per cubic meter of air

• The correct answer is 25 micrograms per cubic meter of air. Your employer is required to make medical surveillance screenings available to you to identify any silica exposure-related health effects if you are exposed to silica dust at or above the action level of 25 micrograms per cubic meter of air as an 8-hour TWA for 30 or more days per year.

– True or False? The HazCom labels on containers provide detailed explanation of the hazards and measures to take to protect yourself, including required PPE.

• The correct answer is False.

– Which actions are included as a part of work practice controls? (Select all that apply.)

Written exposure control plan

Worker training

Keep windows closed near a local exhaust ventilation system

Installing local exhaust fans

Providing disposable PPE

• The correct answer is keeping windows closed near a local exhaust ventilation system.

Keeping windows closed is a work practice that maximizes the effectiveness of the local exhaust ventilation, an engineering control.

– True or False? Inspecting weekly enclosures and seals on the pneumatic transfer system for damage is an example of a work practice control.

• The correct answer is True.

Key Points to Remember

Let’s sum up the most important things you should take away from this session on respirable crystalline silica.

• The health hazards of exposure to silica dust can be crippling and deadly, like silicosis, lung cancer, and COPD.
• Many common activities such as surface cleaning and preparation techniques, milling, polishing, grinding, or other activities that disturb a silica-containing product can expose you to silica dust hazards.
• The crystalline silica rule requires that your employer protect you from exposure to silica dust with control measures.
• Labels and SDSs provide valuable information on the potential hazards of silica exposure to a material, and signs at entrances to regulated areas reduce your chances of exposure.
• Exposures can be controlled by using water, or a dust collection system, and by enclosing the area of the job task to keep other workers away.
• Your employer is required to make medical surveillance screenings available to you to identify any silica exposure-related health effects.