Today on the podcast, co-hosts Mark Reggers and Laurie Wells discuss silica with guest Shari Smith. Shari is a segment specialist in the 3M Personal Safety Division and also a Certified Industrial Hygienist (CIH) and Certified Safety Professional (CSP).
Silica or silicon dioxide is a naturally occurring material in the earth’s crust. Occupational exposure to silica can occur in many different industries including construction, general industry such as foundries and concrete production, and mining. In construction for example, common materials that contain silica include sand, soil, masonry, concrete, granite, rock and certain landscaping materials. When construction workers disturb these materials, respirable crystalline silica can be released. Respirable crystalline silica can present unique challenges for health and safety managers and workers. Tune in to learn more about workplace exposures to silica including applications that may generate respirable crystalline silica, potential health effects, and examples of controls.
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Below is the full transcript of the podcast:
Presenter:
The 3M Science of Safety Podcast is a free publication. The information presented in this podcast is general only, should not be relied upon to make specific decisions.
Listening to this podcast does not certify proficiency in safety and health. You should always seek the advice of a licensed or certified professional in relation to your specific work or task. Always consult the User Instructions for any personal protective equipment you are using and follow local laws and regulations.
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Laurie Wells:
Welcome back to our previous subscribers and welcome to our new listeners. The Science of Safety podcast is presented by the 3M Personal Safety Division. This is a podcast that is curious about the science and systems behind workplace health and safety with a focus on Personal Protective Equipment, or PPE, used to help keep workers healthy and safe.
I am Laurie Wells, one of your cohosts. And I have the great pleasure to have Mark Reggers with me as well. We are occupational health and safety professionals who like to ask questions– why, how, and please explain.
Whether you’re a safety professional, occupational or industrial hygienist, someone with any level of worker health and safety responsibility in your workplace, a user of PPE, or a health and safety nerd like us, this is the podcast for you.
Laurie Wells:
Well, hello, Mark. Welcome back to another episode of the podcast. It’s great to hear you again.
Mark Reggers:
It is great to hear you and also see you. Our listeners may be interested to know that we can actually see each other when we record even though we are in other parts of the world. I’m here
in beautiful, cold Australia at the moment as we’re heading into winter. And you’re in beautiful Colorado. Has summer finally arrived where you are?
Laurie Wells:
Absolutely. It finally has arrived. And you want to know how I know?
Mark Reggers:
How is that? Please tell me.
Laurie Wells:
Well, it’s the sound of summer, that ubiquitous backup beeper of all the construction equipment that’s happening.
Mark Reggers:
I thought you were going to say— Sound of cicadas and animals there for a second.
Laurie Wells:
Road construction is– Road construction happens in the summertime. So yes, we’re finally here.
Mark Reggers:
We are here, but we are also here to introduce our very special guest today and our topic of silica and silica exposures. So, I’d like to welcome Shari Smith from 3M to the podcast today. Shari, please introduce yourself. Who are you? Where are you from? And what do you do in this wonderful world of 3M?
Shari Smith:
Well, thanks, Mark and Laurie. I am incredibly excited to be here today. I happen to be based here in the US, in Minnesota. And I work as a segment specialist in the personal safety division. And I currently support our customers in construction and also the food and beverage industry. And I work as an application engineer.
I’ve had the great pleasure of working for over 20 years helping to keep workers healthy and safe. And I spent over nine years managing an organization of safety and health professionals supporting 3M’s PPE products, such as hearing, respiratory and fall protection, protective and high-visibility clothing
I am currently a certified safety professional and a certified industrial hygienist. I’m also currently the chair of the AIHA construction committee. Thanks for having me today.
Laurie Wells:
Well, this is great. Welcome, Shari. I know you come with a wealth of experience. But I want to start with a very simple question, what is silica, and then follow that up with, why should worksites care about it?
Shari Smith:
Great question, Laurie. Silica or silicon dioxide is a naturally occurring material in the earth’s crust. The US Center for Construction Research and Training reported that workers encounter crystalline silica in many common materials found in construction sites, such as sand, soil, masonry, concrete, granite, rock, and landscaping materials. When workers disturb these elements, respirable crystalline silica dust can be released.
One of the most dangerous forms of crystalline silica is respirable crystalline silica. For the rest of this podcast, we will use the term silica to represent respirable crystalline silica. Respirable particles are less than 10 microns, which are too small to be seen by the human eye. These tiny particles can remain in the air for extended time periods after handling, cutting, or sanding materials containing silica.
Mark Reggers:
Now, you mentioned dangerous forms of crystalline silica is respirable crystalline silica. So can you explain what are some of those potential health effects that make this so dangerous?
Shari Smith:
According to the US Occupational Safety and Health Administration, or OSHA, workers who inhale these very small crystalline silica particles are at increased risk for developing serious silica-related diseases, including silicosis, an incurable lung disease that can lead to disability and death, lung cancer, chronic obstructive pulmonary disease, COPD, and kidney disease.
According to the UK Health and Safety Executive, silicosis can take up to 10 years to develop. The National Institute for Occupational Safety and Health, otherwise known as NIOSH, reports that unfortunately the damage caused by silica exposure can continue for several years, even after the exposure stopped.
Mark Reggers:
So, some very serious consequences there that workplaces and workers really need to be aware of. So, are there any common industries or applications where silica exposures commonly occur?
Shari Smith:
Occupational exposure to silica can occur in many different industries, including construction and demolition processes, which could include concrete, stone, brick, or mortar. Another place that they are commonly found is foundries and mining, refractory production and cutting, concrete product manufacturer, anyone manufacturing engineering benchtops, and abrasive blasting, particularly on sandstone.
Laurie Wells:
Hmm. Interesting. So I’m hearing the back-up beeper, but I’m thinking I might also have some silica exposure to these workers out here. So for those workers in those industries, what kind of specific operations or activities might result in this kind of silica exposure you’re describing?
Shari Smith:
Thanks, Laurie. Any operation that drills, grinds, or cuts silica containing materials could potentially overexpose workers to respirable crystalline silica.
In construction, for example, abrasive blasting and tuckpointing produce some of the highest exposures. One US study reported that 78% of tuckpointers and grinders are exposed to levels above 50 micrograms per cubic meter. And 46% are exposed to more than 250 micrograms per cubic meter.
Other tasks could also expose people to silica, which include block and brick cutting, stationary saw masonry, rock crushing and drilling, polishing and sanding, concrete mixing, and even handling and shoveling dry materials just to name a few.
Laurie Wells:
Wow. So that’s really surprising that tuckpointing is so high. And you’ve mentioned a lot that have to do with construction. What about in general industry?
Shari Smith:
Well, in general industry and maritime, according to the US OSHA and the UK Health and Safety Executive, workers can potentially be overexposed to silica during the manufacture of glass, brick or concrete, or ceramic materials, during the manufacturing of asphalt roofing, artificial stone, or structural clay products.
Another common area is during foundry work, also during hydraulic fracturing by the use of industrial sand in those operations, or, again, the use of sand for abrasive blasting oftentimes in maritime operations.
Mark Reggers:
I mean, how much silica are workers allowed to be exposed to if any is allowed to be exposure to these workers?
Shari Smith:
Occupational exposure limits vary around the world. And in the US and Australia, for example, worker exposures must be below 0.05 milligrams per meter cubed over an eight-hour average. Now, in many European countries, the WEL is 0.1 milligrams per meter cubed. And the ACGIH suggests that workers should only be exposed to 0.025 milligrams per meter cubed.
These newer limits represent a very small amount of material. To put this in perspective, 0.025 milligrams is about the weight of a single snowflake. And a cubic meter is about the size of a small hot tub. So a snowflake in a hot tub is not very much.
This is part of the challenge that we have in training workers and educating them to convince them that the level of silica which can be harmful may be too small to even see. It is very important to understand the regulations, standards, and relevant occupational exposure limits that are applicable to your location.
Mark Reggers:
You’ve done an amazing job just explaining how hazardous and the potential exposures that need to be advised. So for workplaces, how do you or where do workplaces start to think about minimizing worker exposures to silica?
Shari Smith:
Well, regulations vary around the world on the specifics. There’s one thing that’s common across many of them. And that is the use of the hierarchy of controls to reduce exposures to many different types of silica exposures. So, from a substitution standpoint, consider non-silica- containing abrasive blasting materials instead of sand.
Engineering controls for silica could include wet methods, local exhaust ventilation, isolation such as equipment cabs, and cutting tool maintenance, such as keeping the saw blade sharp and operating the blades at the proper speeds to help minimize the amount of airborne silica.
Wet methods could include spraying the area to be cut, polished, or ground with water. Some regulations require the water spray method to be integrated directly into the tool. Where wet methods are not feasible, one could consider local exhaust ventilation methods, such as dust collection systems. Vacuums and shrouds could also be used.
Nowadays, many tool manufacturers offer integrated dust vacuum systems for many silica- generating tools. And when using any of these methods, it’s important to ensure that the disposal of the dust or the filters does not create any additional exposures.
Laurie Wells:
All right. Great tips there and ideas. How about some examples, now, Shari, of administrative controls for silica?
Shari Smith:
Yes. Administrative controls could include training workers on the hazards of silica, materials containing silica on site, tasks that generate silica, how to operate the controls that reduce exposure to silica, and signs that the controls are not working.
Some standards require creating restricted areas to help keep bystanders from being exposed to silica. So, for example, in construction, this could be accomplished by just scheduling around the silica-producing tasks or perhaps using cones to demarcate the silica exposure area.
For general industries, such as a foundry or cement-manufacturing location, this could include having regulated areas or rooms which only allow access to those workers that are wearing the proper PPE or have the proper training.
From a housekeeping perspective, many standards do not permit dry sweeping or using compressed air to clean silica containing waste or dust. So wet methods such as HEPA vacuums and sweeping compounds are often required. Documenting these procedures is often required as part of a written silica control plan.
Laurie Wells:
All right. Shari, I want to pick up on something you mentioned. And that was the proper use of PPE. So, thinking about PPE, can you give our listeners some more information on just how to determine what type of PPE is often considered for silica-generated activities?
Shari Smith:
Certainly. If the engineering controls and administrative controls do not bring the silica levels below the occupational exposure limit in your area, respiratory protection is often needed to control. You will need to conduct an exposure assessment to determine the level of silica exposure. This exposure assessment could be done by a combination of air monitoring and the use of historical data or even engineering calculations.
An industrial or occupational hygienist is commonly consulted to help complete this assessment. And the results will be compared to the applicable occupational exposure limit. In addition, other hazards may be considered such as noise and flying objects.
Mark Reggers:
As we narrow into respiratory protection, there’s lots of different types that we know that are out there. But can you give a few suggestions or some respirators that are often considered for silica- containing dusts?
Shari Smith:
Silica dust is considered a particulate. So respiratory protection options generally fall into two categories. For air-purifying respirators, be sure to consider the appropriate particulate filter and the assigned protection factor. Particulate filters are rated based on their efficiency. Most regulations require filters in the 94% to 99.99% range for silica-containing dust.
For example, in the US, for tasks where the exposure is up to 10 times the occupational exposure limit, a half-mask elastomeric respirator or a filtering facepiece respirator could be considered.
When working in hot and humid conditions, a respirator with an exhalation valve may provide more comfort.
For tasks with exposures greater than 10 times the occupational exposure limit, higher classes of respiratory protection may be required, such as a full facepiece respirator or powered air- purifying respirators or air-supplying respirators. For tasks such as abrasive blasting, there are special abrasive blasting helmets. When using respirators for silica, the respiratory protection program is required in most geographies.
Mark Reggers:
I can only reinforce how important it is to understand the requirements of the task but also the requirements of the person when it comes to selecting and using respiratory protection wherever that may be. As you mentioned in the end there, it’s part of a respiratory protection program. So, what are some of those elements that need to be part of that program?
Shari Smith:
While regulations vary around the world, the basic tenets include exposure assessment, respirator selection, a way to maintain and care the respirators, fit testing of tight-fitting respirators, medical evaluation of employee fitness for wearing the respirator itself, employee training, and record keeping. Due to the potential health hazards of silica, many regulations require medical surveillance of workers exposed to silica as well.
Mark Reggers:
Laurie and I did do some previous episodes on respiratory protection. So, I do recommend all our listeners to go back and listen to those again if you haven’t already. Now, for those other types of hazards, Shari, that may be involved in these particular silica tasks, what are some of these other ones that need to be considered for applications where silica may be exposure?
Shari Smith:
Yes, there can be other hazards and exposures that also need to be considered. It’s important that the health and safety professional doing the risk assessment consider all of the potential hazards and exposures. In construction, for example, silica-generating tasks such as grinding often involve the potential for flying objects and noise.
So in addition to controls and possibly respiratory protection, worksites should also consider eye, face, and hearing protection. Workers may also be working at heights or have the need to enter confined spaces. So once again, it’s really, really important to anticipate, recognize, evaluate, and control all of the potential hazards.
Laurie Wells:
That is a great point, Shari. I’m really glad you mentioned that because it, again, picks up on the theme that we’ve been talking about in previous episodes of our occupational safety and health framework. You mentioned anticipate, recognize, evaluate, and control. And we’ve talked about these in these other– according to these other hazards. So, silica is a perfect specific example of how worksite health and safety professionals can apply those principles.
Well, Shari, it’s really been informative to me. I learned a lot. I’m thinking about the workers in my neighborhood a bit differently now having talked to you. So thank you so much for sharing with us today.
Shari Smith:
Thank you. The pleasure is all mine. And thank you for bringing this important topic to your listeners. It’s important to identify and control silica exposures and to consult applicable regulations. If listeners are looking for more information on silica, please contact your local 3M application engineer. We are here to help.
Mark Reggers:
We certainly are. And, Shari, thank you once again. Laurie, have a great day. And I’ll hear you and see you on our next episode of the podcast.
Well, thanks for listening, everyone. You can listen, subscribe, to and share this podcast through Apple Podcasts, Spotify, Google Podcasts, and most major podcast apps and platforms.
If you have any questions, topic suggestions, or would like some assistance in your workplace when it comes to the appropriate selection, use, and maintenance of PPE, you can get in contact with this podcast by contacting your local 3M office or visiting our website mmm.com. Around the world, we aim to help everyone get the job done safely today, tomorrow, and in the future. Thanks for listening, and have a safe day.
Stay healthy, Laurie.
Laurie Wells:
Stay safe and sound, Mark.
Mark Reggers:
Thanks, everyone. Bye. Bye bye.
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