Reducing Silica Exposure in Manufacturing

Even if you're not aware of it, you come in contact with silica quite often. It happens every time you touch your hand against a quartz countertop, let sand run between your fingers, and brush your teeth.

In fact, silica is one of the most common elements in our physical environments. At a chemical level, it's a pairing of silicon and oxygen, known as silicone dioxide. From a health perspective, it's sort of like salt and water - it contributes to your health, but too much of it can be fatal.

In your day to day life, it's unlikely that you'll be exposed to harmful levels of silica. But on the job, it might be a different story. Silica becomes a serious risk when it becomes respirable - that is, when silica dust becomes airborne and can easily make its way to the lungs.

In this article, we'll go over the risks associated with silica dust generated by manufacturing processes and what employers can do to protect workers from exposure.

The Dangers of Silica

Although silica can be beneficial as a food element and an antioxidant, exposure to airborne silica can be dangerous. Microscopic particles of it can penetrate the internal, causing irritation and permanent damage.

Some of the effects of silica exposure include:

• Silicosis
• Lung cancer
• Lupus
• Arthritis
• Impaired kidney functions

As the name implies, silicosis results directly from exposure to silica. It is a serious and incurable condition characterized by inflammation, scarring, and lesions in the lungs.

The other illnesses listed above are not directly caused by silica. Rather, they result from autoimmune diseases that are triggered or aggravated by the presence of silica dust in the body.

(Learn more about The Dangers of Silica to Your Respiratory System)

Common Sources of Silica Exposure

For the average person, silica ingestion is minor – on par with pollen and other natural and human-made contaminants. Given that most of the Earth’s crust is composed of silica, it is part of our natural environment and our bodies are able to process it accordingly. Even people who ingest too much, for example by taking too many vitamins, will simply flush out the excess through urination.

There are, however, many trades and workplaces in the manufacturing sector where exposure to silica poses a significant risk. Most of these occur wherever stone or soil is impacted and creates dust, especially when quartz is present. Unlike ingested silica, even a very small amount of airborne silica dust poses a danger.

Some workplaces and occupations face a greater risk of exposure to silica. As such, special care to reduce exposure needs to be taken with anyone who works with:

• Raw materials that have a high quartz or stone content
• Technological components that use silica as a base
• Abrasive blasting
• Portland cement
• Power tools (air hammer drills, saws, and grinders) on concrete and stone
• Industrial sand in foundry work or hydraulic fracturing
• Asphalt, grout, concrete blocks, drywall, and certain types of paint
• Old materials like fire brick or insulation that might have degraded from a glassy to a crystalline state

Exposure Levels

Respirable silica particles are microscopic - about 1/100^th the size of a grain of sand. They cannot be seen or smelled, which makes them harder to detect.

Organizations like OSHA established a permissible exposure limit (PEL) based on the amount of quartz detected in a sample of respirable dust, ranging from between 100 μg/m³ for pure quartz to higher values when other particulates are also detectable. This requires sampling and detection tools, along with some calculations. That last component is critical - often, difficulty understanding or performing these calculations contributes to the danger.

New regulations, however, have updated the PEL to 50 μg/m3 of respirable crystalline silica, averaged over an 8-hour day. There is an even lower threshold employers must know - any concentration above 25 μg/m3 is considered action level. This means the work area must be assessed for potential health risks.

Other changes to silica regulations include:

• Restrictions on housekeeping practices that expose workers to silica where other options are available
• Compulsory medical exams, chest X-rays, and lung function tests every three years for workers exposed to the Occupational Exposure Limit (OEL) for 30 days or more per year
• Thorough training on limiting exposure for tasks that expose workers to silica
• Health and safety departments must maintain records of exposure measurement, medical exams, and other data

Adequate protection and exposure prevention is essential. Since dust tends to travel very easily through the air - from ground level to ventilation systems and smokestacks - employers should take measures to prevent exposure to people beyond the confines of the workplace, including residents in the surrounding area.

Mitigating Silica Exposure

Proper management of exposure risk has numerous levels.

Respirators

Since inhalation is the primary exposure pathway for silica-based illnesses, workers and employers sometimes assume that a simple face mask is will provide all the protection they need. In reality, these paper masks are ineffective at preventing silica exposure.

Instead, workers who face a significant risk of silica exposure must be equipped with adequate respirators. At a minimum, these respirators must have a NIOSH rating of N95. This means it will prevent the inhalation of 95% of dust particles. P100 filters will provide even more protection, filtering out 99.9% of the particles.

No matter how effective they are, respirators are not sufficient for keeping workers safe. Rather, they must be used in conjunction with environmental and engineering controls.

Engineering Controls

Engineering controls that can manage the distribution of silica particles include:

• Ventilation systems
• Water spraying systems to prevent dust from becoming airborne, including on cutting blades to prevent the spread of silica at the source
• Enclosures that trap particulates in a designated area
• Vacuum collection systems that pull particulates from the work surfaces and machinery

(Learn more in A Primer on Engineering Controls)

Consider Substitutes

Where possible, the risk of exposure can be reduced or eliminated by substituting silica for less harmful substances. Sandblasting, for instance, can be carried out with other types of abrasives. Likewise, many products that contain silica can be manufactured with components made from other materials.

Administrative Controls

There are also a number of administrative controls that can help workers avoid exposure to silica dust. These include:

• Developing an exposure control plan
• Instituting hygiene restrictions (e.g. prohibiting food and drink in work areas)
• Discouraging habits like brushing dust away from the body
• Discouraging facial hair, which reduces the effectiveness of respirators
• Implementing exposure monitoring and health screening programs
• Ensuring employees’ physicians are provided with a copy of the Physician’s Alert for Silicosis for adequate treatment and to reduce the likelihood of misdiagnosis
• Establishing recordkeeping practices

Conclusion

The dangers posed by silica dust are severe and must not be ignored. Manufacturing workers, contractors, or managers who have concerns should turn to their local health and safety rep for guidance and enforcement.