Silica Part III: How Much Dust is Too Much?

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60mm paver

Silica Part III: How Much Dust is Too Much?


In our introduction to this series on understanding the OSHA PEL, we described what a PEL is and outlined the three factors which determine the PEL: Air, Dust and Time. Here in part III we’re going to explain the second factor: Dust.

There are a few questions we need to answer about dust:

  • How much dust is produced from cutting materials?
  • How much silica is in that dust?
  • How much dust is too much?

Measuring Dust

Let’s start by figuring out how much dust is released from a common cut. For this example we’ll use a familiar material, a standard 60mm paver.

The typical weight for masonry materials is 145 lbs. per cubic foot, or 65,770 grams. This works out to 38 grams per cubic inch. Remember that, we’re going to use it later.

Now let’s look at the dimensions of the cut we’re making. Our depth of cut is 60mm or 2.36 inches, and our length of cut is 4 inches. If we’re using a standard table saw our blade width plus overcut is 0.125 inches. Multiplying these will give us the volume of material removed in a single cut:

2.36 inches * 4 inches * 0.125 inches = 1.18 cubic inches

If we’re removing 1.18 cubic inches of material, and we know that a cubic inch weighs 38 grams, we can calculate the weight of material removed:

1.18 cubic inches * 38 grams = 45 grams

So in one standard 60mm paver cut using a table saw we are removing 45 grams of material.

Converting to micrograms we can start to understand how much dust we’re talking about in OSHA terms:

45 grams
= 45,000 milligrams
= 45,000,000 micrograms


worker cutting block with dustWe’ve determined that one paver cut releases 45 million micrograms of dust into the air. But not all of that dust is silica.

Our tests have shown an average silica content in masonry materials of +/- 20%. If 20% of that dust is silica, we can calculate silica by weight:

45,000,000 * 20% = 9,000,000 micrograms

Through these calculations we now know that 9 million micrograms of respirable crystalline silica is released into the environment in one paver cut.

Great, so what does that mean?


Looking again at the current OSHA PEL:

50 micrograms of respirable crystalline silica per cubic meter of air, or:

50 μg/m3

In other words, for every cubic meter of air a guy breathes, he’s allowed to inhale 50 micrograms of silica.

Let’s go back to part II of this series, where we learned that an average male working at a moderate pace breathes 16.8 cubic meters of air in an eight-hour day. At 50 micrograms for every cubic meter, that means a guy is allowed to breath 840 micrograms in a day within the current OSHA PEL.

And one standard paver cut releases 9 million micrograms.

That’s enough silica to exceed 10,714 days worth of dust exposure.

Using our example, if you were to breathe 100% of the dust from one single paver cut, you’d be breathing over 29 years worth of silica in the OSHA PEL.

We don’t recommend doing that.

So What

Considering these numbers, smart and responsible contractors should understand how dust is measured, how much is too much, and how much their workers are being exposed.

In this example we’ve learned how much silica is produced from a single paver cut relative to the current OSHA PEL. While we know how to calculate the amount of dust being released, we still need to figure out how much of that dust your workers are being exposed to.

The last factor we need to consider is time. For how much time can workers cut, at what level of exposure, and still be within the OSHA PEL?

You’ll have to read Part IV in our series on Understanding the OSHA PEL.

Visit our Silica Dust Home Page. Also check out our dust control power cutters and learn more about what they can do for you and your health.

Previous articles in this series:
Silica Part I: What Contractors Should Know About the OSHA PEL
Silica Part II: The OSHA PEL in Simple Terms

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Comments (44)

  • Don White Reply

    Very interesting helps to understand the math easier. That’s a good breakdown

    October 1, 2017 at 7:43 am
    • Burrell Reply

      This helps me a ton! I was paranoid when I was told that the dust of the driveway blocks that we were cutting were carcinogenic (causes cancer). But then when I read this I was relieved ?. Thank you for making me feel better. Although, I really feel bad for miners. I’ll pray for them. Have a nice day!

      July 23, 2019 at 2:05 pm
      • Sarah Hurtado Reply

        Hi Don, yes, the dust created by cutting driveway bocks is silica dust and is dangerous to your health. Silica dust is not secluded to miners – it effects the entire construction industry. If you are experiencing symptoms of COPDs or Silicosis, please contact your primary physician.

        July 30, 2019 at 9:18 am
      • Elliot Reply

        You were relieved to find that 1 paver exposes you to 29 years worth of maximum silica exposure?

        November 2, 2019 at 8:55 am
  • paul bradley Reply

    please run an example of the PEL, drilling a hole into concrete

    October 4, 2017 at 9:31 pm
    • Walter Reply

      Paul, you can look on the websites for your Power Tool Manufacturer. Just search for the brand you use along with “Silica Objective Data” and you should be able to pull up the reports. You’ll find that even with their top flight dust remediation equipment, you can’t drill many holes and stay under the PEL. I’ve seen one brand (not mentioning the name) that actually uses Concrete at 14% Silica content, which is lower than what you’d ever see in the Construction Market. I’d call that test a ‘cheat’. Basically, penetrating Concrete is bad and if you can find an alternative, you should take it.

      November 2, 2018 at 10:47 am
  • Scott Reply

    Please run one musing a skil saw to cut hardie panel over 8 ft or 6 piece of lap siding stacked on a chop saw! Please is really like to know and I think people need to be informed this way

    November 18, 2017 at 7:38 am
  • Rory Oconnor Reply

    Cutting hardiplank with electric saw,,used respirator part time. Couldn’t s see with mask and safety glasses
    Wegeners vasculitis followed have RA factor

    February 27, 2018 at 11:13 am
  • alan barr Reply

    Been studying this stuff for a long time. Really liked your breakdown here and will check out the rest of the series. Keep up the great work. Cheers.

    April 16, 2018 at 1:50 pm
  • Bobby Robert Reply

    I am cutting, grinding and sanding natural Stone, Flint, quartz.was doing it for days before wearing gloves and mask, then for a couple weeks before wearing more of a respirator mask. What are the hazards.

    April 16, 2018 at 9:25 pm
    • Sarah Hurtado Reply

      Hi Bobby, Check out our silica page. https://iqpowertools.com/silica-dust/

      There you will find some of the hazards of silica dust. We also list other resources for you to find more information.

      April 17, 2018 at 12:04 pm
  • James Reply

    Hello, please help im a bit worried. I cut a hardibacker cement board inside bathroom with a circular saw and didnt know much about the dust. I continued to work in that bathroom for another 6-7 hours. At the end i used a vacuum, but it brought dust up. The next day i used a vacuum as well. Also i used a circular saw to cut outside. What should i do? i just learned about silica dust. How much did i breath in? Chances i already have silicosis? Thank you

    April 30, 2018 at 11:39 pm
  • Cynn Reply

    I recently dry swept a room of about 500 sq ft. The floor was moderately covered in concrete dust and wood chips and I was only bearing an N95 half mask. The rooms main entrance was covered with a large floor to ceiling tarp and I had two windows open at the opposite side of the room. When I thought the dust had settled I sat in that room to eat. I was in that area from start to Finnish about an hour or maybe just over. What risk am I at for developing any Silica related issues?

    July 22, 2018 at 8:52 am
    • Steve w Reply

      Did you have negative pressure?

      October 12, 2019 at 8:54 am
  • Michael Barton Reply

    This has to be the most messed up thing I’ve ever heard about. When I was younger, people told me to shrug off breathing in this dust, little did I know, it’s not only incurable, it’s also fatal (at the smallest doses). Here I am, never having worried about this before, suddenly having trouble breathing, from drilling 3 tiny holes in a ceiling. What I’m reading about it is that I’ll be dead in the next few months. I thought I had to watch out for sun exposure, but that’s nothing compared to this. Needless to say, I’ll be creating awareness of this as much as I can the coming days, never did I ever think, that something so easily prevented, would kill me so suddenly at the prime of my life. Let that be a lesson too, don’t ever trust anyone when they say they know what they are talking about. Here’s to hoping for semi-good news at the doctor’s office tomorrow. Farewell.

    August 30, 2018 at 12:45 am
    • Stewart Reply

      What did you learn from the doctor?

      September 4, 2018 at 7:24 am
  • Stewart Reply

    James, I had a similar experience a few days ago and am worried, too.
    How have things progressed with you? Are you okay? Any symptoms? Visits to doctor?

    September 4, 2018 at 7:26 am
  • Bea Quiper Reply

    Recent bathroom remodel including complete tile replacement. Workers dry cut tile on back porch while there was a huge amount of stuff stored nearby (3 pickup trucks worth of stuff much of it uncovered) and within 5 feet of open back door. They covered nothing, used a broom to sweep everyday for 3 weeks. They finished the job about 3 weeks ago. There is so much dust everywhere now. About a week ago the dust everywhere was so bad my head became completely congested in certain areas and I developed an awful cough which I still have. Tomorrow I have chest X-rays and TB test. I am coughing up blood tinged phlegm now. Yesterday my mom got a terrible cough.
    I started cleaning like crazy when my head became so congested and the more dust I remove, the better for the congestion. If I leave the house or property, I instantaneously have no congestion, so it is obvious it is caused by the dust here and not a cold.
    The workers did a terrible job cleaning up, should never have used a broom, never should have cut any tile in an area so impossible for them to clean up, never should have dry cut the tile.
    There is still so much dust in 1 room of the house (every thing will have to be removed from the room to clean out the dust there’s that much)
    There is much info on worker exposure and Osha rules, but what about this situation where us clients are exposed by worker activities? What warnings should we have been given and who is responsible / liable for the aftermath? Should stuff have been covered and msds sheets or some info on breathing this dust be given to us?
    I was going to ask if exposure such as this -approximately 7 weeks, be enough to cause acute silicosis, but based on the above article about dust from cutting 1 paver, I think you answered my question. Continual Exposure 24/7 to all this dust in this quantity would no doubt cause acute silicosis and it will continue as long as the dust is present. It is such a fine dust and is made airborne by walking on it or even the slightest breeze.
    This is an awful situation. I spent my life working safely and ensuring all the employees at my branch stayed safe while working for me. To think of the potential future I have now, from these irresponsible unlicensed workers, makes me so angry. I can’t believe it.

    October 25, 2018 at 2:49 am
    • Vanessa Salas Reply

      Hi Bea, I’m sorry about your situation. Did you get any advice from a doctor? I’m also concerned because workers cut tiles on the porch before we moved into the house we bought. Not sure if they dry cut or if they used a wet saw. Just curious, did the dust come in from just the back door being open?

      September 21, 2019 at 8:09 am
  • Jim Reply

    I am 60 years old and have been working in the refractory industry for 38 years producing pure crytline quartz silica furnace linings. I work in maintenance so I have done extensive welding which fractures the silica into crytabolite which is a worse form of silica. Also a past smoker and so far have had no adverse effects although I don’t rule it out in the future. Generally the damage takes place over a long period of time.

    January 15, 2019 at 5:10 pm
    • Vanessa Salas Reply

      Hi Jim, just wondering… did you wear a respirator while Welding? Would you continually weld throughout the day? Happy your are doing good 🙂 I’m on this site because I found about 1/2 cup of drywall dust behind my fridge. It’s been back there a year. Only reason why I’m concerned is because drywall has silica and there’s a fan behind the fridge that blows air from the back and it also blows a little air to the front of the fridge. Doesn’t look like the dust was stirred up much since the dust is still there but wondering if the fan has been blowing a little dust or even microscopic particles in the house. Wondering if this is a big exposure. Based off this article it seems like even a tiny bit of dust is hazardous

      September 21, 2019 at 8:22 am
  • James lucas Reply

    I have resentley installed a granite counter top..I die cut the sink opening. With no mask on. It took approx 3-4 hours. I wad breathing the dust the whole time
    .dust is everywhere.. Am I infected?

    April 10, 2019 at 7:26 pm
    • Sarah Hurtado Reply

      Hi James, sorry to hear about your experience. Every time dust is released into the air you are breathing in that silica dust.

      June 25, 2019 at 11:51 am
  • Nilfiskcfm Reply

    Very useful information. Industrial vacuums are one of the best options to remove silica dust.

    May 2, 2019 at 2:23 am
  • Brian Matthews Reply

    A company that is on the job with us said they performed a test that proved osha wrong.we have to use hammer drills with vacuums attached they said they don’t because of the test they performed showed they would have to drill 170 holes a day to be harmful.when they may drill maybe 20 or 30.that company is Griffin electric.they say they are exempt from that osha rule the rest of us follow.could this be true from their testing?

    June 13, 2019 at 9:22 am
    • Sarah Hurtado Reply

      Hi Brian, thanks for commenting. We cannot say yes or no to this question without reviewing their test data. There is no way for a contractor to be exempt. They might be following Table One or they are following engineered controls. Either way they are not exempt. To better answer this question please contact OSHA directly for more info.

      June 25, 2019 at 11:54 am
  • Janetta medeles Reply

    I work at a frac sand mine. For about the last month and a half I hve been working in the silos loading trucks. The dust collectors are not hooked up yet and I’m really worried that I have inhaled way to much of the dust. I hve been working about 75 hours a week in the silos and now I have developed a cough when I am sleeping.my company does not provide us with anything but a paper dust mask (which has been proven to not to protect from silica). I am also nauseous alot of the time. Please help me understand if I may be in serious risk. I believe I am but none of the supervisors or higher ups seem to care.

    June 27, 2019 at 9:25 pm
    • Sarah Hurtado Reply

      Hi Janetta, we cannot determine if you are at risk without knowing your exposure to the silica. We recommend air monitoring so that you know how much silica is in the air you are breathing while performing certain work practices. However, you might want to bring these symptoms up to your primary physician. Silica is a serious issue. You can review our silica page https://iqpowertools.com/silica-dust/ to understand air monitoring an date TWA more. You can also visit https://www.lung.org/lung-health-and-diseases/lung-disease-lookup/silicosis/ to understand the risk and symptoms with silicosis.

      June 28, 2019 at 10:30 am
  • Vanessa Salas Reply

    My husband used to work mixing cement in buckets with water for a company for about 10 years, off and on so maybe he really only worked 5-7 years. Some days he wouldn’t mix cement. He said he would never wear a mask. He would usually mix it outdoors and when the dust would come up he would just back up from it. This was when he was in his 20s thru 30s. He will almost be 40. Is he at risk for silicosis?

    August 31, 2019 at 6:25 pm
    • Sarah Hurtado Reply

      Hi Vanessa, your husband may have been at risk for silicosis. We are not doctors, so I can’t say for sure, but I would recommend getting checked out. His exposure to dust may lead to other issues like COPDs.

      September 3, 2019 at 1:14 pm
      • Vanessa Salas Reply

        Thank you Sarah. After I sent you this message I found about 1/2 cup of drywall dust behind my refrigerator. I read drywall dust has serious additives like silica and mica. I vacuumed it all with a hepa vacuum but was just worried that possibly a little bit has been blowing in the house because there’s small fan behind the fridge that blows air from the back of the fridge and blows air to the front of the fridge. Normally I would not be worried but the fan behind the fridge has me concerned and the fact that the dust has been there for 1 year. My fridge is, however, in a cut out space with a counter on the left, cabinets on top and a wall to the right . The fridge condenser fan goes through a cycle of blowing air for 15 minutes straight and then it turns off for 15 minutes straight. Seems like the air was not enough though to truly stir up the dust since the dust is still there but just wondering…. if microscopic amounts of dust made its way out from behind the fridge or from the front, Into my house, would it be enough to cause lung damage or health issues…. I will reach out to a doctor soon but does this seem like a big exposure? Thank you

        September 21, 2019 at 8:43 am
  • Dan C Reply

    the math used assumes that all of the dust created is respirable which is a technical term for the size of the particles. only silica particles 10 micron and below are small enough to enter the lowest area of the lung and cause silicosis. 9 million micrograms of silica is likely an over estimation.

    September 2, 2019 at 8:00 am
    • Vanessa Salas Reply

      Hi Dan C., your comment is very interesting and makes total sense. A company cut a small piece of drywall behind my fridge a year ago . I found about 1/2 cup of drywall dust behind my refrigerator last week, they obviously didn’t clean all the dust. I read drywall dust has serious additives like silica and mica. I vacuumed it all with a hepa vacuum but was just worried that possibly a little bit has been blowing in the house because there’s small fan behind the fridge that blows air from the back of the fridge and blows air to the front of the fridge. Normally I would not be worried but the fan behind the fridge has me concerned and the fact that the dust has been there for 1 year. My fridge is, however, in a cut out space with a counter on the left, cabinets on top and a wall to the right . The fridge condenser fan goes through a cycle of blowing air for 15 minutes straight and then it turns off for 15 minutes straight. Seems like the air was not enough though to truly stir up the dust since the dust is still there but just wondering…. if microscopic amounts of dust made its way out from behind the fridge or from the front, Into my house, would it be enough to cause lung damage or health issues…. Do you think the drywall dust caused from cutting drywall has Respirable silica in it or is the Respirable part of the silica only Respirable during the cutting and not from the dust left behind?? Thank you

      September 21, 2019 at 8:53 am
    • John Reply

      Dan – good point. Actually “respirable” size is 4 microns and smaller, so the aforementioned estimation is even more exaggerated

      November 15, 2019 at 11:23 am
  • Bob Reply

    Thanks for this info, Im 20 and ive been labouring full time for 2 years now in construction, i regularly cut concrete/cinder blocks and jackhammer. I also mix concrete all the time and have been doing all these things almost all year, Im working on an indoor pool at the moment and the dust floats around for ages after i cut, i always have a vacuum though it still shoots a large amount of dust in the air. Sometimes after cutting i can taste the dust in my mouth and every afternoon when i finish my boogers are completely grey. I had no idea silica existed in concrete till now so thank you. hopefully ill be sweet

    October 14, 2019 at 9:53 pm
  • Annette frisbie Reply

    The contractor cut my granite counter top inside my home, when installing it. There is thick dust everywhere requiring all items in the kitchen be wiped down. The air conditioner filter was clogged and required washing. Is there any exposure to my family

    October 16, 2019 at 4:43 pm
    • Sarah Hurtado Reply

      Hi Annette. There would be exposure if you were in the room where the countertop was being cut while it was being cut. Without air monitoring we can not say for sure you were exposed to the respirable silica or not. However, it sounds like the dust could contain silica. If you are concerned about the exposure, you should contact your doctor.

      October 17, 2019 at 1:08 pm
  • Ruth Snook Reply

    Hi, does anyone know if sanding off paint causes silica dust. My son is a diabetic and a house painter, and plasterer, and never seems to wear a mask. He’s been doing this for well over 25 years. Thank goodness he doesn’t use lead base paint.

    October 20, 2019 at 6:14 am
    • Sarah Hurtado Reply

      Hi! Silica dust is created by grinding products such as stone or other products comprised of quartz. We cannot say for sure that the paint does or does not contain silica. However, I would recommend your son wear a respirator while doing any sanding or plastering.

      October 22, 2019 at 9:02 am
  • Tom Reply

    From everything I have read, my conclusions are this. People who live at home or did something for one day may have been exposed to silica but the risk of contracting silicosis is so small for these people that it shouldn’t be worrisome…otherwise a lot more people would have it, rather than a hundred people that die from this a year. It’s mainly workers in the business that have to worry. Going to a doctor for this will mean nothing unless you have real symptoms. There are too many variables here that are not mentioned. How many of the 100 (all workers) smoked? What are the percentage of workers that are doing this kind of work actually contract the illness. I think for some of the posters here, the ones that are not construction workers, are worrying needlessly.

    December 16, 2019 at 5:55 am
  • Tom Reply

    To put it in perspective, it is estimated that 10,700,000 people work in construction in the U.S. Let’s say that only 5% work with silica (535,000) which is probably a very low number than actual. 100 deaths a year from silica would be a tiny, tiny fraction of 1%.

    December 16, 2019 at 6:09 am
    • Jim Reply

      1% is a huge number, that is one out of every one hundred exposed.
      Nearly all that work in construction are exposed to silica.
      Silica is the second most abundant thing on earth, the only thing that is more abundant is oxygen.

      January 20, 2020 at 5:13 pm
  • Willie Leggett Reply

    It’s actually 1/100th of 1 percent. So basically one out of every thousand. And that’s using Tom’s conservative estimate of 535,000 workers exposed to silica in the US. That being said, it doesn’t matter how small the percentage is, if you are in the percentage that die. It makes more sense to wear a respirator. I read the N95 respirator grade blocks 95% of the crystalline silica, but after wearing one today I feel a constant need to clear my throat and a numbed burning sensation in my chest. If I go into work tomorrow and the symptoms persist or get worse I’m quitting.

    February 24, 2020 at 8:06 pm
  • Sue Reply

    Dry sanded our living room and kitchen for about 4 hours total over a two day period while we were In the home.
    Only two windows open for ventilation.
    What is the likelihood we have deviled acite silicosis?

    November 1, 2020 at 1:23 pm

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