Safety of Galvanized Steel in smokehouses/grills

A. Should be fine for a cold smoker. Watch out for cadmium coating, though in some old fridges.

A. The original question of this string has someone who intends to (and possibly did, it was a long time ago) use an old refrigerator for his smokehouse. I've been reading a lot and came across someone saying specifically that old refrigerator racks should be avoided because they are cadmium plated.

Here is the source, it's the third comment, by "FlyFish":
www.chowhound.com/post/smoking-safe-galvanized-garbage-284991

I also remember reading something about refrigerators and lead, but I don't have a source for this.

All in all, even if it's late I think this should be strongly advised against.

!! Your comment should be a lesson in the reason for meaningful research. I know this but yours was a wake-up call.
Thanks eh!

Michael lee Evans
- Kailua, Hawaii
July 15, 2022

---

!! Thanks Rick! Your posting motivated me to look a bit harder for an authoritative source like the National Institutes of Health -- and, yes, I see "Cadmium poisoning from a refrigerator shelf used as an improvised barbecue grill" by Timothy D. Baker and William G. Hafner at
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1929634/

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Brian,

Disclaimer: I'm not taking any responsibility if your 'galvanized' box has Cd plating (or if something else fails, either). Use this advise as a safety guideline and don't try anything unusual - > you should be safe. The 'galvanized' smoking box is presumably coated with zinc, i.e., gray colored metal possibly with the distinctive surface patterns. We generally don't get enough zinc in our nutrition and generally a small increase in gain is welcome as extra zinc washes off from our body and does not accumulate like many other heavy metals. To ensure adequate gain of zinc, zinc gets to be added into our fertilizers in many parts of the world.

For an average human the *safety limit* here in Europe these days is as much as 1 mg of zinc daily per body kilogram. Perhaps somebody can quote local daily limit if it differs.

If an average person weights 70 kg (or 175 pounds), such a person can take safely about 70 mg of zinc daily. The amount of zinc a person *requires* daily is far less, though.

(Though, during pregnancy women *require* about double amount of zinc than humans usually. As I recall, lots of zinc is required for cell division that happens during pregnancy).

(For example for metallic lead the same safety limit is 3.5 µg daily per body kg. Lead accumulates into our bodies, too which is a disadvantage).

So I suspect your zinc galvanized steel is safe for food manufacturing as long as the (sour) food juices do not come into direct contact with the zinc plating of your smokebox. I recommend you use some sawdust powder on the bottom of your smokebox to prevent the dripping acidic juice of fishes from corroding the galvanized plate on the bottom of box. (Oh, you already did that - WOW !)

The fumes from some burning sawdust powder and burning flesh that occurs in the smokebox generate PAH compounds that can cause cancer too, but that's not under discussion here. Generally, most or all extra zinc we get washes off from our bodies but at least the standards do not recommend more than total daily gain of 1 mg/kg here in Europe. (No more than that even for pregnant persons).

Sincerely, Mr. "Know-it-all"

A. Well, Larry, zinc metal, the main ingredient in most 'galvanized' platings, melts at 692.68 K -or- 419.53 °C -or- 787.15 °F. But there are other plating metals, too. Demand zinc plated sheets - make sure you got zinc plated sheets first before constructing a smoker.

It's not recommended to keep the smoking box on open fire either, as it might cause the zinc metal to (partly) melt (and oxidize which would cause excessive zinc fumes ruining the cook). Please wait until the fire mostly dies out -to embers. Please cover the fire facing metal plate completely with (alter) sawdust. (I think alter smoke is what most people in Finland consider the best for smoking fish and food?)

Perhaps also, a completely iron box made of iron sheet metal or discarded, burned oil barrel would suffice for you for your 1-time or 1-summer use. The rust inside the barrel gets to be converted mostly to magnetite by heat and moisture coming from the cook. Magnetite somewhat prevents rusting of the barrel and the rusty old oil barrel may well last one summer and turn black (=rust turning into magnetite).

A. Hi Michael. Although zinc is not considered a "food-safe" surface, the coating on the cistern was once considered safe enough to drink from. Zinc itself is an essential micronutrient, not a poison, and I doubt that it will poison your meat under normal circumstances ... but at the least, with no food in it, get it as hot as you'll ever get it, as a first attempt to keep any residue off your food.

But it is always dangerous to use things for purposes for which they weren't intended for two reasons: first, the designer didn't intend this use and may not have foreseen it and may have used something somehow that you and I are not aware of -- we're calling it galvanized, but do we really know? Secondly, we have accumulated no body of public knowledge to warn us -- no epidemiologist anywhere is doing a study on: "The potential hazards of conversion of early 1900s East Texas galvanized cisterns into meat smokehouses" :-)

Regards,

A. Hi Duke. Yes, most of the zinc probably burned off. Surely very little of it came off onto your chicken in even the worst case, and zinc is a micronutrient not a poison anyway. Personally, I'm not a paranoid, sky-is-falling, guy -- so I wouldn't hesitate for a second to eat the chicken. But hopefully this will help you understand the principle of the thing:

1. Zinc is not considered a food-safe surface because certain foods can at least theoretically dissolve some of it into your food, and as a matter of practice you don't want dissolved metal in your food.

2. Fencing was not intended to be cooked on, so:
  a. There is no guarantee that the fencing has a pure zinc coating rather than some experimental material that might be fine for fencing but not good to cook on. Who knows?
  b. When we use a material for a purpose for which it wasn't intended, there are no researchers, epidemiologists or government agencies tracking whether any problems are occurring due to it. So not only do we not actually know if the situation is a problem, but we never will unless the effect were truly dramatic ... like multiple people dieing on the spot at a barbecue :-)

Regards,

A. Hi, David. I'm no expert, only the website administrator. Cadmium electroplating would not have ever been used on trash cans in my estimation, although I haven't studied the history of that trash can manufacturer. If you see the typical "spangled" look of hot dip galvanizing, then you have further confidence that they were galvanized (dipped in molten zinc).

My personal opinion is I don't think there's any problem with what you are doing as long as you and the readers realize that there is to be no contact with the galvanized surfaces (because galvanizing is not a food-safe coating).

But any time you re-purpose materials that were not intended for food service, and introduce them into the food preparation cycle, you have the problem that regulatory authorities and medical researchers generally don't do research on it. Once in a while you may find a United Nations WHO article about it if it's a common third world practice -- but not finding such articles is not proof that such re-purposing has been found to be okay. Sorry, but that's just the way it is -(

Regards,

A. This is in response to the steaming fish with the galvanized garbage cans question. I wouldn't do it based on a recent experience I had where I was using a brand new galvanized watering container (made for animals to drink out of) as a way to put water vapor into the air (on top the wood stove). I got sick for four days after about 4 hours exposure to the vapor. It might not have been that, but I had all the symptoms of metal fume fever.

Just my two cents ...

A. Hi, Cary.

Per my response to David, my personal opinion is that it's not a problem. But then again, who do I think I am that people should rely on my guesses over their own?

The issue is that a real investigation of whether it's dangerous or not will probably never be done. To test one prescription drug costs millions of dollars and involves a rigorous protocol where exact dosages are administered under exact conditions, and the psychological factors are eliminated by nobody knowing who is taking the placebo vs. the real thing.

So that sort of real answer will never be forthcoming. On the other hand when something is really and obviously dangerous -- like mercury vapors in hat making, chromium fumes, or lead in paint -- it usually comes out fairly quickly. So we can probably say that a trash can smoker is significantly less risky than those :-)

Regards,

There are no experts in this topic, Craig, but I would not do it.

It's not so much even a matter of real danger in my opinion; rather, it's that as a business I feel you should not take the shortcuts that an individual might for his own use. I think you should absolutely use 'professional grade' materials (stainless steel) throughout if you are selling anything made on it.

Hi Ed. As you see, we appended your inquiry to a thread where the topic has been discussed at length for years. Good luck.

Regards,

Hi Kari. Thanks! But the Alzheimer's Association does not really agree with you about the link to aluminum. I think the main reason aluminum is rarely used is the melting point is too low (it's easy to melt aluminum cans in a BBQ pit).

Regards,

A. Hi Kari. Thanks for the chart.

I don't advocate for or against zinc vs. aluminum. What I advocate for is science & common sense & calm; what I advocate against is "toxic timebomb in your kitchen!" news reports, because they make our short lives less pleasant while richly rewarding news organizations and politicians for causing heartache and paranoia.

I am 100% open to the possibility that aluminum is not good for us but I must rely on competent researchers to make those determinations, and quoting the Alzeimer's Association:

These organizations may change their opinion, and if & when they do, I'd probably change mine. Thanks again.

Regards,

A. I've been using a galvanised trash can as a smoker for a few years now. It sits on top of a portable gas ring. The safety angle hadn't occurred to me until last week, when someone was horrified at the thought of zinc fumes in food.
My response was that a) (as has been said in this thread many times) zinc is an essential trace mineral and you can buy pills of it, b) breathing fumes is not the same thing as eating them. Yes you can get sick breathing the fumes, as you would welding or whatever, but ingesting the small amount that adheres to any smoked food should do no harm and may be beneficial.
The bottom has almost rusted out of my can now, so obviously the zinc has gone.

A. Hi David. If you're sure it is galvanized, not something else, it doesn't really seem to be a significant concern.

Regards,

A. Hi, Scott. I think refrigerator shelves are nickel plated rather than zinc plated these days. Whether nickel or zinc I don't think it's anything to worry about for support of lava rocks -- if you get them good and hot and nothing happens to them, they stay shiny, then they are probably either stainless steel or nickel plated, either of which would be okay.

The problem is that if they're really old they might be cadmium plated -- and that's actually very dangerous.

Regards,

A. Hi Chad. Instead of worrying about it, why not burn a small bag of charcoal in it before connecting it. I assume the cabinet is new enough to not have to worry about lead paint?

Luck & Regards,