Possible health risks of working with silicon carbide

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maximus83

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We've had a few folks in threads recently mention dangers of inhaling diamond particulate, especially when using them dry. I think there is also some risk of working with silicon carbide. The key dangers being skin contact with a probable carcinogen, or inhalation of crystalline silica that could damage your lungs.

Some states in the US, NJ is one example, list silicon carbide as a hazardous substance. Of course it's possible they could be overreacting and over-regulating as some states are known to do. Or, they could be on to something, as the science suggests some risk, and perhaps we need to be cautious around these materials. I honestly don't know, not a medical researcher. I'm also not usually a reactionary, and definitely not a "dandelion eating tree hugger" type either. :) But this seems real, if you browse the sources below. Note that in the NJ suggested guidelines, they offer a lot of suggestions like avoiding skin contact, inhalation, contact with eyes, avoiding eating in the work area around SiC, handwashing and washing clothes carefully after use, etc. It's odd, I have read similar types of guidelines for folks who do a lot of shooting, especially at indoor ranges, to minimize lead exposure. I follow those precautions and urge others to at my range where I am an NRA certified range officer. Many shooters I know have scorned this, for years, and then a guy I know personally who's an instructor of frequent pistol training classes, himself, learned he had serious and prolonged lead exposure from years of working in indoor ranges with poor ventilation and poor 'lead hygiene' practices. And some workers at a local pistol range who were removing accumulated lead got seriously ill for exactly the same reasons.

A few interesting resources I ran across on the risks of working with SiC:
ETA adding these 2 resources, the Oregon guidelines are about "silicosis" and "crystalline silica", but has some really useful steps for working around sharpening abrasives. Like using your stones wet. The doc also contains some outdated information, suggesting that silicon carbide is a "substitute" that does not contain crystalline silica. OR OSHA told me that is outdated information and is going to be updated.
Do with this what you will: ignore, or take precautions. I am certainly not advocating panic, nor of getting rid of SiC, and have no plans to throw out my SiC stones. But will take some common sense precautions as suggested in the NJ and Oregon guidelines (the bolded articles). I think also, if I were working around high speed grinding equipment that involved SiC abrasives, I would at least be checking out options for safe work area including air filtration or particle masks. But that's me, better safe than sorry. If anybody reads this and takes any common sense step that keeps you a little safer, it will have been worth the time to post the info.
 
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Thanks for warning!

I believe the risk is pretty much nonexistent for a recreational weekend tinkerer like me. I don’t use powered abrasive, often using oil on my DMT, and reprofiling only new knives. For EDC, mostly it’s touching up.

For a pro it may be a concern giving the volume they work on. Again, much appreciated!
 
Chris "Anagarika" said:
Thanks for warning!

I believe the risk is pretty much nonexistent for a recreational weekend tinkerer like me. I don’t use powered abrasive, often using oil on my DMT, and reprofiling only new knives. For EDC, mostly it’s touching up.

For a pro it may be a concern giving the volume they work on. Again, much appreciated!
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^This.

When sharpening with SiC by hand, i.e., by unpowered means, I've never noticed much or any airborne dust issues. The grit that comes off a SiC stone is relatively coarse, and even heavy enough that it sinks in water (I've noticed this when using a SiC stone in/over a sink; all the grit ends up on the bottom). And being that I use it with oil anyway, dust is a non-issue entirely. I've used dry, powdered SiC at 600 grit for applying to stropping media, and I've even noticed it doesn't tend to get airborne very easily; it's messy, but seems to settle easily and quickly onto whatever work surface I'm using.

For powered sharpening with SiC belts throwing lots of dust into the air, I could see it being a significant hazard, and taking precautions for that would be worthwhile, as is the case with most abrasives used as such, and for airborne metal dust as well. More so, for pros working at heavy volume and in great frequency, obviously.


David
 
Increased risk was not linked to SiC particles, once cristobalite exposure was controlled for. Studies of SiC users in various industries did not reveal an increased risk of lung cancer.

I treat it as a hazardous substance, but not an outright dangerous one. Stuff has been around a long time.

I am much more concerned with metal dust esp steels with high alloy content. Any time I'm using the belt grinder with or without a mask, the belt is wet, the part is being dipped often, and the belt is running at fairly low RPM. I seldom use any of my manual stones without a wetting agent.
 
That's me too. ^ There is all sorts of inhaled materials we are exposed to weekly. Back the week before Thanksgiving I was traveling on the road and some bug (flu or viral) was in the dust and I breathed it. From that I got a sinus infection, had to get on antibiotics and stayed a week in bed recovering. And I hadn't even been in my shop or near my sharpening stones. So, your going to get stuff you don't care for. DM
 
It's most dangerous as an airborne particulate. Don't breathe it in and you're fine. It's literally made from silica sand and sawdust fired in an electric arc furnace, so the material itself is low risk--it's more of an issue of constant exposure to particulates without PPE, just like aluminum oxide. It's otherwise quite safe, and of no risk at all in manual stones.
 
Added a couple more resources to the list. The Oregon guidelines are actually quite useful and suggest some possible routes of exposure (including some things we all do) and suggests some practical guidelines for reducing exposure. One of them is working with your stones wet. Another interesting side note, is they say that working with aluminum oxide is a 'substitute' that does not expose you to crystalline silica. Another interesting, and confusing detail that I don't get, is that they list "silicon carbide" as a material that doesn't expose workers to crystalline silica. I guess that's good news for manual sharpeners, but contradicts some of the other info....

ETA: Called the OR OSHA folks, they said that particular line item in their doc is actually outdated, and is going to be removed. There are new more stringent fed guidelines on the level of safe particulate, and also, they said that USING SiC abrasives GENERATES the crystalline silica as you use it. So, they are actually agreeing with the other docs despite this outdated item. Updated above, inline.
 
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maximus83 said:
Added a couple more resources to the list. The Oregon guidelines are actually quite useful and suggest some possible routes of exposure (including some things we all do) and suggests some practical guidelines for reducing exposure. One of them is working with your stones wet. Another interesting side note, is they say that working with aluminum oxide is a 'substitute' that does not expose you to crystalline silica. Another interesting, and confusing detail that I don't get, is that they list "silicon carbide" as a material that doesn't expose workers to crystalline silica. I guess that's good news for manual sharpeners, but contradicts some of the other info....
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It makes sense, in that silica (SiO2, a.k.a. 'silicon dioxide') and silicon carbide (SiC) are completely different materials, physically and chemically. Silicon, contributed from aluminum silicate in the original process, and from sand (SiO2) and other materials in other processes, is used to make SiC. But, once the SiC is formed by bonding the silicon and carbon, any silicate used to make it ceases to exist as such in the new material. It's chemically consumed by the process.

People involved in the manufacture of SiC from the raw materials, or in the mining of the raw silicates used to make it, I assume might still be at risk for exposure to airborne silica dust.
 
Don't know if you saw my updated "ETA" in that post, which I just added after calling them to understand the contradiction. They said that info that SiC is a 'substitute' is outdated and is going to be removed. The other stuff in the doc, like the precautions to minimize exposure, they said are still valid and will probably be updated as well.
 
FortyTwoBlades said:
Again, manual sharpeners have nothing to worry about. The issue is when it gets airborne in volume like during mechanical grinding operations.
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I think this is PROBABLY true. I'm not quite as confident as you are though, in particular on the 'probable carcinogen' aspect which hasn't been studied that well yet. For myself, the risk seems low enough that I plan to keep using my SiC stones. But using them wet, handwashing after, no eating/drinking in the sharpening air, etc., aren't that hard to do and seem like reasonable safety things to reduce risk. I think though like I said above, if doing a bunch of high speed grinding, I'd be checking out more involved steps.
 
I would really not be nearly so concerned. Dosage makes the poison, and SiC is chemically stable and inert. Carcinogenic effect is limited to SiC "whiskers", not granular particles.
 
maximus83 said:
Don't know if you saw my updated "ETA" in that post, which I just added after calling them to understand the contradiction. They said that info that SiC is a 'substitute' is outdated and is going to be removed. The other stuff in the doc, like the precautions to minimize exposure, they said are still valid and will probably be updated as well.
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I wonder, in the ETA note, re: SiC generating crystalline silica as it's used, what specific uses they're referring to(?). It'd have to be something capable of unbonding the silicon from the abrasive's molecular structure, to then recombine with oxygen to form silica, which I'd think couldn't happen without some serious heat (powered grinding, maybe?). I doubt it's something that could happen by manual means, such as sharpening by hand on a SiC stone.
 
i've seen some recent stuff on silica in the construction industry.
lots of construction materials contain it in various amounts, and many of these materials are cut and/or sanded on a regular basis. i think this is part of the reason that you are seeing and increase in the concern over silica as a possible carcinogen.

asphalt, brick, cement, drywall, plaster and tile to name a few.

non-mechanical sharpening is no concern for me
 
If the person sharpen's with water or oil using Silicon Carbide I would not worry if they were sharpening and using the stones dry then I would worry about the dust.
 
I honestly wouldn't even worry about sharpening dry. Obviously don't put your face right up to a dusty stone and make vigorous intakes of breath, but almost all of the very small amount of dust generated in dry sharpening with SiC remains on the stone proper, and what little goes airborne stays pretty localized to the stone. Most people have their faces well away from such. I think simply keeping in mind "hey--try to keep the dust out of your lungs" is probably sufficient caution as far as manual sharpening is concerned. With all power sharpening a dust mask should be used, but that's best practice regardless of the abrasive being used.
 
maximus83 said:
a "dandelion eating tree hugger" type
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The latest science is that if you eat dandelions occasionally and hang out with trees it will render the SIC inert and you will feel much more relaxed as a "side effect".
:)

I would like to see a study that shows how many of the people getting all about this is smoking a cigarette as they pass the regs or read and "worry" about the warnings.
o_O :confused:
 
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