Reducing Silica Exposure in Manufacturing

Whenever you touch a piece of quartz countertop, let sand run between your fingers, or brush your teeth, you come in contact with silica.

It's one of the most common elements in our physical environment, a chemical pairing of silicon and oxygen, known as silicon dioxide. From a health perspective, it has much in common with salt and with water: it contributes to your health, yet too much of it can be fatal.

The dangers of silica have to do with its physical makeup, especially as it's found in places like manufacturing plants. Silica can turn to dust that can enter the body through the lungs.

The Dangers of Silica

Although silica can be a beneficial food element and an antioxidant when ingested in the correct amounts, the effects of exposure to airborne silica can be dangerous. As microscopic particles of rock penetrate the internal organs, they can cause irritation and permanent damage, including:

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

Silicosis, as the name implies, results directly from exposure to silica. It is characterized by inflammation, scarring, and the development of lesions in the lungs. While it might sound like a modern condition to those who aren't familiar with it, it has been around since the Ancient Greek and Roman eras – potters, masons, sculptors, and others who worked with stone all did their work while breathing air laden with silica dust.

The other illnesses are not directly caused by silica. Rather, lupus, arthritis, and kidney function impairment result from autoimmune diseases that are triggered or aggravated by the presence of silica dust in the body.

Common Sources of 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 take too much by mouth, 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. It takes only a very small amount of airborne silica dust to be dangerous. Special care to reduce exposure needs to be taken with anyone who:

• Works with raw materials with a high quartz or stone content
• Manufactures high tech components that use silica as a base
• Engages in abrasive blasting
• Works with Portland cement
• Uses power tools (air hammer drills, saws, and grinders) on concrete and stone
• Works with asphalt, grout, concrete blocks, drywall, and even some types of paint
• Works with old materials like fire brick or insulation that might have degraded from a glassy to a crystalline state, through devitrification

Exposure Levels

The particles of respirable silica are 1/100^th the size of a grain of sand, and they cannot be seen or smelled. Organizations like OSHA have 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 and some calculation ability, and very often the difficulty in performing or understanding the calculations contributes to the danger.

It has also been suggested that the current minimum threshold is still too high and should be adjusted to 50 μg/m3. Safety professionals overseeing workers who are exposed to levels above that range are encouraged to protect their workers from exposure, even if the levels are considered permissible by OSHA standards.

Adequate protection and exposure prevention is essential. Since dust tends to travel very easily through the air from ground level through to ventilation systems and smokestacks, this applies not just to manufacturing workers. Employers should also take measures to prevent exposure to people in a wider radius, including residents and business owners within the area.

Mitigating Silica Exposure

Proper management of exposure risk has numerous levels.

Use of Respirators

Since breathing is the primary source of silica-based illnesses, face masks are sometimes assumed to provide sufficient protection. Silicosis experts, however, attest that paper masks are ineffective.

Similarly, respirators should only be used in conjunction with engineering and environmental controls, not as a primary tool. A job site must attain complete physical control of the environment, and if that is not sufficient to bring the particulate count to an acceptable level, then respirators, including sufficient training according to NIOSH standards, is obligatory.

Engineering Controls

To control the distribution of silica particulates, job sites must incorporate:

• Adequate ventilation
• Dust control through wet processes, such as water sprays and water delivery to cutting blades
• Use of enclosures to trap particulates in a confined area
• Vacuum collection systems that pull particulates directly away from the work surfaces and machinery
• Prohibition of activities that encourage dust, such as dry sweeping and driving vehicles quickly through high dust areas

Consider Substitutes

Exposure risk can also be mitigated by using silica replacements in activities like sandblasting as well as manufacturing processes. A wide selection of alternatives, ranging from steel to organic products can be used as abrasives, adhesives, or components.

Administrative Controls

Finally, but equally importantly, there are administrative controls, which include:

• Developing and communicating an exposure control plan
• Enforcing awareness of operations that create crystalline silica exposures as well as preventative steps and practices
• Instituting hygiene restrictions, such as prohibiting food or drink in work areas, providing emergency shower facilities, eyewash stations, and change rooms with shower and vacuum facilities for complete changes and cleaning of clothing
• Discouraging automatic habits like brushing dust away from the body
• Discouraging the growth of mustaches and beards that reduce respirator effectiveness
• Discouraging smoking, which compounds lung damage and health risks
• Encouraging awareness and adherence to all health and safety regulations, as well as opportunities to report dangers and procedural failures
• 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 avoidance of misdiagnoses
• Establishing stringent 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.