Silica is almost everywhere you look. It's one of the most abundant minerals in the Earth’s crust and materials like sand, concrete, and mortar all have high silica content. Silica or materials with high silica content are used in glass, pottery, ceramics, refractory bricks, and artificial stone.

About 2.3 million Americans are exposed to silica at work, especially workers in construction (concrete), oil and gas (fracking), manufacturing (sandblasting), and agriculture.

But if silica is so abundant and part of everyday objects, why is it considered a workplace hazard?

The reason for concern is that workers are exposed to silica in a different form. Handling bricks or decorating our walkway with stones is fine, but drilling, cutting, or smashing through them releases small particles of crystalline silica that can then be breathed in.

Over time, breathing in crystalline silica can lead to:

  • Silicosis
  • Lung cancer
  • Chronic obstructive pulmonary disease
  • Kidney diseases

These conditions are no walk in the park, and the first three can be fatal.

In this article, I'll cover some of the things you can do to protect workers whose jobs might expose them to respirable silica.

What OSHA Standards Apply to Respirable Crystalline Silica?

OSHA has issued two new respirable crystalline silica standards to protect workers from the hazards associated with this material and to provide guidance for employers developing procedures and programs to protect their employees. One standard is strictly for construction industry (OSHA 29 CFR1926.1153), while the other is general and for the maritime industry (OSHA 29 CFR1910.1053)

OSHA has started enforcing the construction industry standard on September 23, 2017, while the enforcement for the general standard started more recently, on June 23, 2018.

Protecting Workers Against Silica

We have to implement the most effective controls to minimize the hazards of inhaling crystalline silica.

Ideally, we would substitute the material or process with one that negates the hazard entirely. Most of the time, however, we have to resort to lower level protective controls, or a combination of them (learn more about The Hierarchy of Hazard Controls).

Here is advice for how to protect workers from exposure to silica, in order from the most effective (elimination or substitution) to the least (personal protective equipment).

Elimination or Substitution

As with any other workplace hazard, eliminating the hazard is the most effective control.

Below are just a few examples of elimination and substitution methods that are effective in mitigating silica hazard.

  • Use a less hazardous material (for example, when sandblasting substitute sand and glass with nut shells, corn cob, garnet, plastic balls, steel grit, or even dry ice)
  • Try to change your formwork design to minimize the use of concrete finishing
  • Change your process to one that generates less respirable silica, such as splitting pavers rather than cutting them
  • Replace sandstone grinding wheels with ones that use an abrasive like aluminum oxide
  • Use magnesite or aluminum oxide bricks in furnaces instead of silica bricks

Engineering Controls

When eliminating the hazard is not feasible, the second-best option is to engineer the process so that it separates the employee from the hazard. In the case of silica, that means finding ways to prevent the silica from becoming airborne and mix with the air our employees breathe.

The two most common ways of achieving this are to either collect or isolate the silica at the point of generation or to weigh it down with water.

Collecting or Isolating Silica

Combining local exhaust ventilation and a vacuum cleaner can decrease the concentration of respirable crystalline silica by an average 95%. There are a variety of systems commercially available, from fixed systems for shops to mobile solution for individual tools.

Though the airflow of different ventilation systems varies with the application, an airflow of approximately 70ft3/min is adequate and will achieve these kinds of results.

Water-Based Controls

When using pneumatic, hydraulic, gas powered, or electric saws, applying water to the blade at the manufacturer recommended flow rate (0.5 l/m to 2.5 l/min, depending on toll and application) is a very efficient way of wetting the respirable silica particles and preventing them from becoming airborne. Water control cuts the respirable crystalline silica by approximately 90%.

Following the flow rate is the best way to ensure these results. Using less water will not be effective, while applying more will not provide any additional benefits.

It is worth noting that the silica can become airborne again as it dries. It is a good idea to gather and dispose of the mud generated by cutting (do not dry sweep).

Administrative Controls

No control program works without proper communication and awareness.

When exposure to respirable crystalline silica is a concern, we should develop and communicate an exposure control plan. This plan should then be reviewed and updated annually.

Administrative Controls in Construction

According to OSHA’s Respirable Crystalline Silica standard, employers in the construction industry should:

  • Establish and implement a written exposure control plan that identifies tasks involving exposure and methods used to protect workers, including procedures to restrict access to work areas where high levels of exposure may occur
  • Designate a competent person to implement the written exposure control plan
  • Restrict housekeeping practices that expose workers to silica where feasible alternatives are available
  • Offer medical exams, including chest X-rays and lung function tests, every three years for workers who are required by the standard to wear a respirator for 30 or more days per year
  • Train workers on work operations that result in silica exposure and ways to limit exposure
  • Keep records of exposure measurements, objective data, and medical exams

Administrative Controls for General Industry

OSHA’s Respirable Crystalline Silica standard for general industry and maritime industries adds the following requirements:

  • Assess employee exposures to silica 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
  • Use dust controls to protect workers from silica exposures above the PEL
  • Provide respirators to workers when dust controls cannot limit exposures to the PEL
  • Train workers on work operations that result in silica exposure and ways to limit exposure

Both standards call for a respiratory protection program, as per OSHA Standard 29 CFR 1910.134.

Personal Protective Equipment

PPE is important to workplace safety, but it is the least effective form of hazard control. PPE should always be considered in conjunction with administrative controls at a minimum, but your program will be strengthened if engineering controls or elimination can be brought into the mix as well.

Skin Contact

There are no guidelines for selecting clothing to avoid silica coming in contact with skin, but it is a good practice to prevent skin contact, especially since silica is sometimes associated with corrosive materials (such as cement).

Eye and Face Protection

Eye and face protection can be provided with any safety glasses (class 1A) or goggles (class 2A or 2B) that are suitable for dust protection. Hoods (class 5A and 5B) and shields (class 6A and 6B) can also be used (find out How to Choose the Right Safety Eyewear for Your Job).

Repsiratory Protection

According to 2016 OSHA regulations, the Permissible Exposure Level (PEL) for respirable crystalline silica is 5mg/m3. Above these levels, a respirator is required. Respirators equipped with the N95, R95, or P95 filters provide an adequate degree of protection. N99, R99, P99, N100, R100, and P100 filters are also suitable, but will not provide a sizable difference in protection when compared with the filters mentioned above.

These respirators can be used only of the silica concentration is less than 10 times the PEL.

Regardless of filter type and number, a fit test should be performed when wearing a half-face or full-face mask to ensure proper fit. Without a proper seal, the user is at risk of inhaling dust.

When the silica concentration is more than 10 times the PEL, a supplied air respirator is required. It provides a superior degree of protection and also protects the eyes.

Conclusion

Exposure to crystalline silica can result in life-threatening chronic conditions and significantly reduce quality of life. Protecting workers from exposure is not optional.

By following the advice laid out in this article, you should be able to keep your workers productive without causing them harm.