Can some steels be bad for our health ?

[Nemo3000]

No, you won't get cancer by using CPM-REX45 but, there is a "but": is the use of any high Cobalt steel asking for more care about the way we use it.

The question has shined after I had posted my last review on the Tree Rex, a Shaman exclusive run using the CPM Rex45 high cobalt steel.



https://nemoknivesreview.com/2020/02/07 ... ymondwood/

And my friend Max Wedges told me:

“Careful with the knives you use with food (specially acid food). The problem is that COBALT is a Cancer agent. For any steels that are sharpened often & go close to food, I avoid ALL Cobalt steels (Tungsten Carbides are less of an issue). If you sharpen you always get some “swarf” residue on the blade… better clean it properly before use: use a cotton swipe with alcohol & a drop of tea tree oil, after carefully washing & drying the blade (& avoid the grinding dust like the Pest it is). M4, M2 Steels have no Cobalt. CPM S110V, N-690, VG-10 do, so I use the older S90V, S35VN, RWL-34/CPM154, 440-C or AEB-L for food knives. Were I a knife maker, I would totally refuse the use of any steels containing Co. Moly is related to Tungsten: these are much less harmful, and are bound into Carbides… but Cobalt forms no carbides & gets airborne easier. Be wise?”

That’s very interesting ! It is something to discuss.
How a steel could harm your health is a subject which I have not seen yet on forums. (Forgive me if it was al ready discussed.)
(Another example of care is the way we sand G-10 or Carbon fiber: their dust is very bad for our lungs for example or anything we applied on our blade to protect them...)
Steel is not neutral. If you cut a green salad with carbon steel, the leaf will get brownish in a matter of minutes. The same cuts with a stainless steel and the salad will stay green for hours. Steels are not neutral with the matter they separate.
So could a Powder Metallurgy Tech steel using 8% of Cobalt be poisonous at some end ?

I have found that:
"Chronic exposure to cobalt as a metal, fumes, or dust has been reported to cause respiratory disease with symptoms ranging from cough to permanent disability and even death, respiratory hypersensitivity, progressive dyspnea, decreased pulmonary function, weight loss, dermatitis, and diffuse nodular fibrosis."
from:
https://ntp.niehs.nih.gov/ntp/htdocs/ch ... st_508.pdf

"Cobalt dust was nominated for toxicology and carcinogenesis studies based on widespread occupational
exposure and the occurrence of occupational disease, i.e. hard metal disease, associated with exposure to
cobalt and its compounds, including cobalt tungsten carbide. The carcinogenicity of a soluble cobalt
compound, cobalt sulfate heptahydrate, in experimental animals exposed by inhalation has been recently
demonstrated. Limited data are available to assess the chronic toxicity and carcinogenic potential of
inhaled insoluble cobalt compounds, particularly cobalt metal dust."

More on Cobalt:
https://www.livescience.com/29275-cobalt.html

So what are your thoughts ? Could some steels be somewhere bad for our health if we sand, grind, resharp them without care?
What do you think ?

[Albatross]

I think a lot of the data comes from exposure to pure cobalt, whereas the amount of cobalt in a knife blade is only a small part of it's ingredients. Hap40 is the same as Rex45, and it's used in Japanese kitchen knives. Maybe the chefs out there know something about it's hazards or safety.

For anyone concerned about cobalt, try to use other knives for food prep, and also wet your sharpening stones during use, to keep potential dust to a minimum. In my opinion, wetting stones is a good idea for any steel.

Hopefully someone here knows definitively, whether or not we're in the clear with these high cobalt steels.

[Pancake]

So what are your thoughts ?

If someone stab you in the chest with a knife, it would be pretty bad for your health :D

[Nemo3000]

I think a lot of the data comes from exposure to pure cobalt, whereas the amount of cobalt in a knife blade is only a small part of it's ingredients. Hap40 is the same as Rex45, and it's used in Japanese kitchen knives. Maybe the chefs out there know something about it's hazards or safety.

For anyone concerned about cobalt, try to use other knives for food prep, and also wet your sharpening stones during use, to keep potential dust to a minimum. In my opinion, wetting stones is a good idea for any steel.

Hopefully someone here knows definitively, whether or not we're in the clear with these high cobalt steels.

Yes this is a good point HAP40 been used in kitchen knives. :-)

So what are your thoughts ?

If someone stab you in the chest with a knife, it would be pretty bad for your health :D

Yes that and swallowing a Shaman for breakfast is not recommended too.


Another article and another point of view:
https://www.jayfisher.com/Food_Safety_K ... rcinogenic

Quote: "One of the most highly touted and recommended knife blade steels pushed by Asian knife cutlery firms is VG-10. This steel contains high amounts of cobalt. K390 contains even more cobalt. There is a distinct lack of regulation in cobalt-containing alloys, and you might wonder why this is so. You are not alone in noticing this danger posed by grinding and sharpening these knives. It's up to you whether you allow this substance in your environment."

Also that:

"Sharpeners Report, 2013
As recently as 2011, the National Toxology Program revised and listed Cobalt-Tungsten Carbide as one of six items added to its Annual Report on Carcinogens. The NTP published that Cobalt Tungsten Carbide is “reasonable anticipated to cause cancer.”

As a precaution, ventilation, dust collection and filtration systems, and respirators are likely to be very good investments. Filtering Face piece respirators are divided into various classes based on their filtration capabilities."


ELU (End Line Users) are not suppose to turns their blades into dust too ! ;-)
But what amount could be harmful ?
Would a patina avoid any risk ?

[Notsurewhy]

The inhalation issue is more for miners or people in an industrial setting using grinders. If you're going to take a powered sharpening system to a blade, you should probably use a respirator, but I doubt you'll be making significant amounts of airborne dust with stones or strops. That's a good rule regardless of cobalt. Lungs don't like metal dust.

As far as ingestion, Cobalt is necessary for life in small amounts and toxic in larger amounts like many other minerals. I seriously doubt you could eat enough to cause an issue from using a knife for food prep. Maybe if you're sharpening daily and licking the stones clean?

[pantagana23]

Nickel anyone?

[Nemo3000]

The inhalation issue is more for miners or people in an industrial setting using grinders. If you're going to take a powered sharpening system to a blade, you should probably use a respirator, but I doubt you'll be making significant amounts of airborne dust with stones or strops. That's a good rule regardless of cobalt. Lungs don't like metal dust.

As far as ingestion, Cobalt is necessary for life in small amounts and toxic in larger amounts like many other minerals. I seriously doubt you could eat enough to cause an issue from using a knife for food prep. Maybe if you're sharpening daily and licking the stones clean?

Yes !! Sharpening and not wiping the blade would perhaps be an issue if you do that every single day for a very long period of time.
Like a butcher, a cook ?
ELU are not professional sharpeners anyway. and Those steel stay sharp very long time....And I have noticed they prefer stropping to metal removing diamonds.... :-)

[bearfacedkiller]

It is a risk for knife makers but they should be wearing respirators.

I have zero concerns about doing food prep with a knife with cobalt in it.

I generally make a habit of not licking my sharpening stones when I’m done.

[araneae]

I would guess that there is no risk to the average knife user and that we are exposed to many more carcinogens in daily life that we should worry about first. If knife blades were dangerous enough to worry about, there would be regulation. Unless you are powdering and huffing your blade on the daily, I'd guess you are pretty safe.

[Nemo3000]

It is a risk for knife makers but they should be wearing respirators.

I have zero concerns about doing food prep with a knife with cobalt in it.

I generally make a habit of not licking my sharpening stones when I’m done.

But I do lick my blades to clean them after a lunch !!! . :-D

[The Mastiff]

Any powder from grinding or sharpening should be avoided whether it contains cobalt or not. If it is cleaned off before food is cut everything should be fine.

I try not to over complicate things too much as life can be complicated enough. IMO, this is one of those things and worrying about cobalt in the steel is not something I'm going to spend time on.

[RustyIron]

Non issue.
Risk approaches zero.

[Nemo3000]

OK we are all agree it should be zero risk for the ELU.

Now what about the knives makers?

Dust goes everywhere....

[bearfacedkiller]

Knife makers should wear respirators of some sort.

Plus, I am sure OSHA is making sure that larger knife factories are well ventilated. I have been a blue collar guy all my life and when I have worked for larger facilities OSHA was always watching us.

[eRoc]

Maybe if you're sharpening daily and licking the stones clean?

Wait. Am I not supposed to be dipping my fine stones into colored sugar? :D

[Nemo3000]

Nickel anyone?

Dober dan !

"Cobalt has few, but highly specialized, uses in alloy steels. Its behavior is similar to nickel, in that it forms a complete series of solid solutions with iron at elevated temperatures and is also extremely soluble in ferrite. It is a potent ferrite strengthener; this solid solution strengthening persists to quite high temperatures, and cobalt is therefore found in several grades of high speed tool steels, among others. Like nickel, cobalt is ferromagnetic. This led to its use in a series of magnetic steels as well as the widely-used Alnico alloys. Cobalt is an important constituent of the 18% Ni maraging steels and several other ultrahigh strength steels and is added to one grade of austenitic stainless steel."

Bok bok !!

IMO, this is one of those things and worrying about cobalt in the steel is not something I'm going to spend time on.

On blade steel use to cut things, certainly.
but:
"Cobalt poisoning can also occur from the wear and tear of some cobalt/chromium metal-on-metal hip implants. This type of implant is an artificial hip socket that is created by fitting a metal ball into a metal cup. Sometimes, metal particles (cobalt) are released as the metal ball grinds against the metal cup when you walk. These metal particles (ions) can get released into the hip socket and sometimes the bloodstream, causing cobalt toxicity."

But for good measure...
Chromium Poisoning Just as Dangerous as Cobalt Poisoning. :D
Link here: http://www.moriarty.com/depuy_hip_recal ... Poisoning/

A good reason to ban all stainless steel !!! :D

Wait a minute...
"Historically, cobalt toxicity became a recognized clinical problem after recreational consumption of beer with a foam-stabilizing agent containing cobalt sulphate or cobalt chloride. The addition of cobalt to beer was considered to play a key role in the development of the low-output ‘beer-drinkers’ cardiomyopathy, first described in Quebec, Canada, in the nineteen sixties."

Na na na ! Beer is sacred !!
Give me my CORONA !! What virus ?...... CHeers !

[Mike Blue]

These pages build on the principle that you have to know for yourself what the risks are and what risks you are willing to take. Being informed is critical before making a decision like this. Information based on the rumor du jour is not healthy.

Cobalt is a natural component of FOOD. The beer drinker's cardiomyopathy was real for three years between 1964-67. It appeared to be cobalt toxicity BUT other factors were likely to have complicated the presentation as the amount of cobalt ingested was less than expected for the effects described. Cobalt assimilation occurs only by intake of vitamin B12, and not in its ionic or metallic form. There is no clear recommendation for the amount of cobalt. In vitamin B12, and its minimum daily requirement, it is available in the amount of 5-8 micrograms per day.

The scary recommendation is to avoid FOOD altogether. Don't drink water either. You can't avoid it, your body has a need for a little of it and is built (designed or evolved) to adapt to the presence of it.

In 35 years I've seen every chemical associated with blacksmithing or bladesmithing come under fire for what it will do to a human being. Most rumors fall to pieces when even reasonable searches are completed. By the way, no chemical seems approved for use in California. Some human beings seem to live for propagating rumors and half truths and do nothing to improve the content of their own minds before leaving others sleepless and anxious.

I knew a girl with exquisite sensitivity to nickel. Not the nickel bound to steels in knife blades, but the inside of the button on her cheaper fashionable jeans. The rash on her belly looked like she'd been burned with a propane torch. Once she knew it was the pot metal button, her fix, because she would not give up fashion jeans that were cheap, was to paint the surface of the button with nail polish. When her belly began to tingle, she painted her nails and her jeans button. A simple barrier prevented the problem.

That's an example of a superficial reaction. The human skin is quite resilient when it comes in contact with all sorts of things. Soap and water will take care of a great many problems. Moisturizers get the majority of the minor percentage left over. But some, no matter what, are going to react.

Inhalation is another animal altogether. If the MSDS sheets recommend a good mask (think minimum HEPA), then wear it. If you make knives, seriously consider a means of dust abatement. The lungs do not easily rid themselves of ultra fine dust. Not everyone visiting will react to your shop dust the way you do. You have to consider other people better than you think of yourself. But this is grinding or industrial exposure and those effects are pretty well described with just a little research.

It'd be amazing if polishing the patina off a using knife would produce a lethal dose of anything.

[zhyla]

VG-10 has like 1% cobalt and it’s in all kinds of kitchen knives. I would assume it’s perfectly safe when bound together with iron.

[JMM]

So what are your thoughts ?

If someone stab you in the chest with a knife, it would be pretty bad for your health :D

'Tis but a scratch!

[Nemo3000]

These pages build on the principle that you have to know for yourself what the risks are

Sorry, which pages you are talking about ? :)

It'd be amazing if polishing the patina off a using knife would produce a lethal dose of anything.

But would a cobalt steel lose some cobalt in the cutting material process ?
No proof of that yet.
Would a patina be some kind of isolation as patina seems to protect steel from pitting ? I don't know.
Would cobalt steel grinding be more unhealthy than non cobalt steel grinding ?
As I said G10 dust is already very unhealthy, are the same level of filtering used for some 8% cobalt steel dust ?

VG-10 has like 1% cobalt and it’s in all kinds of kitchen knives. I would assume it’s perfectly safe when bound together with iron.

1% is not 8%. And VG10 is stainless.
Now cobalt in alloys used for cutlery seems to be a new trend hence the REX45 sprint runs coming, the HAP40 (8.5% Cobalt) great success and the VG10 we use since 1995 (Bill Moran FB01 was the very first) VG10 is stainless and got less amount of cobalt (1.5%). But REX45 got more cobalt than any other components.
Cobalt is obviously not cyanid, it won't kill you in an instant but it is known for its toxic nature.
But like copper handles which can be toxic but also a natural antiseptic use on hospital door knobs... how Cobalt can alterate your health.
So far, we have found some advice which can be taken or not, for mostly being cautious mostly based on the fact cobalt is toxic.
8,5% is a lot in a steel destined to be in contact with food... but many Japanese Chef knives use this alloy. So even if they stain, we can assume they won't poison our food.
But here it is only assumption. I haven't found any proof yet. :)
Hence my question again.



For information Radium (radioctive) was used in the begining of the 20th century as a panacea... We found later it was not such a good idea. The same for the workers painting clocks hands with radioactive paints...
Absence of proof is not proof of absence.

Cobalt poisoning is certainly a bigger issue into the way lithium batteries (cobalt is used there also) are recycled.
:)