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Aug 11, 2006 02:39 PM

Copper wok, anyone?

Hello, hounds-

Hoping some of you might help. I bought an all-copper (unlined) wok on a trip to China last February and have some concerns:

1. Does copper need to be "seasoned" like other metals? I use the wok about twice a week since I bought it and am wondering if it will eventually develop a non-stick surface like carbon steel models. It seems to be taking an awful long time. FYI, I have read "The Breath of a Wok" and there is no mention whatsoever of copper woks.

2. Also wondering if copper will discolor food or have an adverse chemical reaction with certain ingredients? I have been tempted to cook SE Asian food in it, but am afraid the dishes might be discolored through the use of coconut milk, lime juice, or tamarind.

3. I am also concerned if there are any toxic consequences from using copper cookware over a period of time. Should I fear copper poisoning?

I look forward to your feedback. Thanks!

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  1. Copper is highly reactive, especially with acids and may produce harmful products. Yes, you should be concerned about toxicity! If you leave it out it will darken over time, but this is NOT seasoning, it is oxidation which will reverse when you heat it.

    Are you sure this is pure copper? It's a soft metal, easily tarnished, dented and scratched, so by itself does not make good cookware. Most copper pots are lined and still need a lot of work to maintain the finish.

    2 Replies
    1. re: cheryl_h

      Hi Cheryl,

      Thanks for your feedback. I suppose my wok must be made with some kind of alloy, as it is very heavy, unlike what you describe. Too bad about the toxicity--guess I won't be cooking in it anymore. It's really a shame, as it's handmade. You can see the metalsmith's indentations on the surface. I guess it'll now sit in my kitchen just for show :(

      1. re: marachino

        I'm not sure what in Cheryl's post gave the impression that copper isn't heavy - it's actually quite dense, and good copper cookware (in the range of, say, 2 to 3 mm thick) is very heavy for its capacity. So, your wok could still be pure copper, which I recognize is no help if you want to cook in it. Although it does scratch, stain, and tarnish quite easily, thick copper is plenty sturdy enough to hold up in daily use all by itself - the lining, whether tin or stainless steel, is there to separate the food from direct contact with the copper, not to provide any added strength (which tin couldn't do in any case as it's even softer than copper.

    2. Call around to some high end,independant cookware shops and get the name of a place that relines copper cookware. You could have it lined, though I'm not sure whether the high heat wok cooking would be detrimental to tin linings or not.

      2 Replies
      1. re: mattrapp

        That's a good recommendation - I don't know why I didn't think of it! Here's a link to one retinner: It's not cheap, though, and you're right that the high temperatures of wok cooking may be a problem - tin melts at around 450 degrees F and I've melted some of my tin linings accidentally over medium heat just by not paying enough attention to what I was doing .

        1. re: mattrapp

          Tin lining in a wok is a bad idea as tin has a fairly low melt point and a wok gets heated quite high with nothing but a little bit of oil. This is definitely not an appropriate application for tin lined copper.

        2. Hi Marachino - I see that this post is now 6 years old but I came across it doing a search and wanted to reply since I have exactly the same question. I'm guessing that your copper wok was purchased either in Kashgar (where there are many copper smiths) or in northwest Yunnan (Lijiang, maybe). Especially in Kashgar, there is lots of beautiful and relatively inexpensive handmade copper ware. To clarify - these pots/woks do not appear to be lined with anything but copper and I believe they are pure (or at least mostly copper). I've read lots of contradictory info online about whether or not cooking on raw copper is a good idea or not. Seems that there still isn't scientific consensus on this matter - or can someone else out in the food-knowledge-ether weigh in? I bought a copper wok too, but I am also confused about how to care for it and what/how I can cook safely. Any more info would be most welcome - I'm an American who's lived in China for more than eight years. This is my first chow hound post. I'll be happy to help with any China/Chinese food related questions in the future...but, like Marachino, I'm stumped on copper woks......

          22 Replies
          1. re: huoguofengzi

            Hi, huoguofengzei:

            You are right that there is not much *informed* consensus on whether cooking on bare copper is always to be avoided. Yes, bare copper is more reactive than tin or SS, but unless what you're cooking is quite acidic, you're not going to get much of a dose. Witness all the unlined jam, confectionary, polenta and zambaglione pans, not to mention mixing bowls. Perhaps we should add woks to this list if they have a history in parts of China.

            Bear in mind that, unless you already have way too much copper in your system, about the worst that could happen is that you have some gastric upset. Relative to copper pans themselves, tinning hasn't been around all that long, so I find it doubtful that we'd have had *any* bare copper pans if they were truly toxic. Nevermind copper's role in Ayurvedic medicine. Or the pervasiveness of brass pans in India and Pakistan.

            Still, I wouldn't store acidic foods in bare copper, and I would NEVER serve food from a pan that showed any green copper salts--which are very toxic.

            I'm with TraderJoe on it being a bad idea to tin a copper wok. You would be constantly flirting and skirting with the melting temp of tin (437F). I'll also observe that woks and wok cooking seem to be uniquely ill-suited to thick copper. This is one of the few places in cooking where you may *want* hotspotting and highly uneven heat.

            If you get a chance, look around Lijiang and Kashgar and see if and how the copper woks are being used. I would appreciate it if you post what you see and hear.


            1. re: huoguofengzi

              <I bought a copper wok too, but I am also confused about how to care for it and what/how I can cook safely>

              Why would you want to cook with a copper wok? It goes against what a wok should do. Yes, the fast heat transfer aspect of a copper is good, but other than that, everything else is bad. First, you cannot tin the wok because wok cookings should be done at very high temperatures. Second, it is very important to have a nonstick like surface for a wok. Thus, seasoned cast iron and seasoned carbon steel woks are ideal tools, not stainless steel, not bare aluminum, not copper. Foods will stick to a copper wok at high temperatures. Therefore, completely hindering the stir-fry aspect. Third, in wok cooking, you want to have a very high temperature surface. Having copper to distribute the heat all over the entire wok is unnecessary, and counter-productive.

              Copper toxicity is well documented. It is a bigger problem for children and elders. It is nowhere the same as lead poisoning, but it is real nontheless.

              1. re: Chemicalkinetics

                Thanks for the reply Chemicalkinetics. Interesting, I hadn't actually thought about the advantage/disadvantage of a highly conductive metal like copper in a wok. Nor did I think about the stick/non-stick factor. I use a run of the mill iron (or steel? it's confusing, for me, not having much knowledge of metallurgy, because the word in Chinese people use to refer to this type of wok is 铁 (tie - meaning iron) but the appears is closer to carbon steel (i think?---not cast iron, anyway). I take great pleasure in the golden brown to black non-stick surface I've built up from cooking in and seasoning the wok again and again. Hadn't stopped to think that wouldn't be possible with copper. I'm now feeling perplexed by copper woks too - in fact, although I started this thread by saying I'd bought one already, I was actually simplifying for the sake of putting the question out there. I take students to Kashgar every semester, so the reality is I've been thinking about buying one, but wanted to know more about cooking with copper before I did. Now I'm thinking another type of pot might be a better choice...

                1. re: huoguofengzi

                  The Chinese do not call carbon steel or cast iron woks. They are classified in a different system. They distinguish wok as raw iron (生鐵) or matured iron (熟鐵). 铁 can mean either, so I have no idea what you have, aside that it is not copper, stainless steel or aluminum...etc.

                  <so the reality is I've been thinking about buying one,>

                  You can buy one if you like. I just don't see the point.

                  There are plenty people here are health conscious. They are concern of aluminum and Teflon cookware. What I can tell you for sure is that the toxicity of copper is well documented compare to aluminum and Teflon. while the toxicity from Teflon cookware is very questionable and unproven, which is why the US government has no restriction on cooking on a Teflon pan. Copper toxicity usually comes as the form of acute, but there can be many chronic effects as well. In simple terms, copper can cause long term damage blood cells, liver and I believe kidney as well. This is why copper cookware has to be lined to be sold in the US. Again, it is much more severe with children and elders. In other words, you may be perfectly healthy while cooking in a copper wok, while a child won't be.


                  Like everything in life, chronic symptoms are much milder than acute symptoms, but by the time you notice any chronic damages, then it is nearly impossible to reverse the damages.

                  Interestingly if we are concern of copper toxicity, I would guess that the copper leaching from a wok is much lower than the copper leaching from a soup pot.

                  1. re: Chemicalkinetics

                    Ah! Thanks very much for explaining the 生铁(sheng tie, raw iron) 熟铁 (shutie, mature iron) categories. So are these equivalent to carbon steel and cast iron or different mixes of metals? If 熟铁 (I'm using the simplified characters here - I'm guesing you might be from Hong Kong or Taiwan originally?) is cast iron and 生铁 is carbon steel, then my wok must be carbon steel. It's certainly not cast iron.

                    And now I am duly freaked out about unlined copper. I do wonder though, with all of the unlined copper cookware in Xinjiang and other areas, wouldn't people have noticed by now if it was causing health problems? That said, if symptoms are mainly gastrointestinal, attribution might be tricky.

                    Thanks again for your responses here (and on my knives).

                    1. re: huoguofengzi

                      Most of the so called iron woks are carbon steel woks. I should be more specific and more clear that the Chinese often categorize wok in 3 classes. The 生铁, 熟铁 and 钢. In other words, raw iron, mature iron, and steel. You can read it here in baidu -- last paragraph:


                      Often the definition of 熟铁 includes the 钢, and this combination of 熟铁 and 钢 is very similar to the English definition of carbon steel. The definition of 生铁 is similar to cast iron. Although the direct translation of cast iron is 铸铁. In short, different countries have different definitions, and it is difficult to force them to be direct translation. You live in China. You should know there are many words which have no literal translation. For example, often English translation of Chinese or Japanese warriors going to battle to die in honor, but you know that is not what they mean. They did not really die for HONOR in the English sense. If anything, they die for what is considered as "義" which has no good English translation -- more closer related to righteous or duty.

                      <I do wonder though, with all of the unlined copper cookware in Xinjiang and other areas, wouldn't people have noticed by now if it was causing health problems? >

                      Well, keep a few things in mind. The Roman used lead for a long period of time without fully understand of its poisoning aspect. The ancient Chinese hermits used mercury as a major ingredient for immortality. Do you think mercury can lengthen life spans? Coca cola was first sold as a cure all medicine with the active ingredients from cocaine. If the so called intellect Roman and Chinese can use lead and mercury, and modern Americans can use cocaine as medicine, then it is not surprising that Xingiang people use exposed copper cookware. Keep in mind that many things appear more toxic nowday because we live so much longer. In merely two hundred years ago, people average lifespan was about 40 years. Human used to die very early. Well, if you are going to die around 40 years old from infection diseases and warefares, then you are unlikely to have the privilege of getting diabetes or cancers or atherosclerosis. Now, as human lifespan have been lengthen to 80+ years, you will see many people suffering from diabetes, cancers, atherosclerosis. The increase in cancer occurrence does not prove modern lifestyles cause cancers. The mere fact of living longer will increase the rate of cancers.

                      Again, you may noticed that many people here worry about using aluminum cookware or Teflon cookware. I can unequivocally point to cases of real copper poisoning, while others can only "guess" or "feel" there are cases of aluminum and Teflon cookware poisoning. And if aluminum and Teflon are indeed toxic, then you have to wonder why it took them so long to figure out too.

                      Again, that being said and all, copper poisoning is certainly not the worst there is. For most people, your body should able to clear out this excessive copper and you should be fine. Nevertheless, at the end of the day that copper poisoning is indeed real, and that was the reason why copper cookware in US is lined with tin or stainless steel or something.

                      1. re: huoguofengzi

                        Hi, huoguofengzi:

                        Before anyone gets too freaked out about copper poisoning from cookware, we ought to be given some *actual* cases of it happening (not from other sources). Remember, EPA considers a lifetime of ingesting 1.3mg/L of copper in potable water to be *completely* safe. That's actually a lot.

                        And don't be fooled: unlined copper pans are perfectly legal and available in the US. See, e.g.,

                        More than half of all US homes have bare copper cold and hot water pipes. Think about it.

                        Finally, ascorbic acid (good 'ol Vitamin C) both inhibits adsorbtion of copper and chelates it from body tissues (If you have too much, and more Americans have too *little* copper in their systems).


                        1. re: huoguofengzi

                          <mainly gastrointestinal>

                          Gastrointestinal is certainly common. However, as mentioned, there are other toxic effects as well, and these other symptoms are worse. Excess copper can cause hemolysis, liver failure..etc

                          Unlined copperware is not used very often in modern countries. Despite all the worries about Teflon cookware, we have not have a death related incident, and certainly no epidemic. To look at copper toxicity effect, we have to look back into history to an area where people used to regularly use bare copper cookware, like India. Indians still do so, but not nearly as often as it used to and certainly not for infants. Indians have significantly decreased the use of copper to boil/store milk for infants, and I pray no one does this anymore.

                          Indian Childhood Cirrhosis (ICC) is a very nasty disease which unfortunately is often fatal. It is probably one of the strongest cases to illustrate the lethal effect of copper -- very clear cut. It has been shown to strongly correlate with copper intake.

                          "A common killer disease of the past, Indian childhood cirrhosis (ICC), which became preventable and treatable in the early 1990s, is now rare.... Environmental ingestion of copper appears to be the most plausible explanation for ICC, as shown by feeding histories"


                          In this 1982 article, a set of twins were reared separated. The first twin consumed milk stored in copper containers developed ICC with a firm and enlarged liver. The hepatocytes showed copper containing proteins, and the serum and urine have high level of copper . The second twin consumed milk stored in stainless steel containers did not develop ICC and live healthy. Based on a control experiment, the article concluded that "The source of excessive copper seems to be copper cooking utensils".


                          Another article from 1994:

                          "Indian childhood cirrhosis is generally believed to be caused by toxic excesses of hepatic copper derived from milk boiled in copper vessels."

                          Another following article has stated:

                          "Of the cirrhoses that affect Indian children,
                          Indian childhood cirrhosis (ICC) is a discrete clinical and histologic
                          entity in which large amounts of copper are deposited in
                          the liver. The evidence linking copper deposition to increased
                          dietary copper intake in infancy was reviewed. Prevention of this
                          feeding pattern prevents ICC, and the disease has now largely
                          disappeared from many parts of India....."


                          It is fortunate that ICC has largely disappeared from India and nearly forgotten, but it was once a real and common death-infliction disease.

                          As I have mentioned, a given copper dosage to an adult may be safe, but toxic to children and seniors. ICC is a good analogy to your Xinjiang question. You asked why wouldn't Xinjiang people know about copper toxicity. You can ask the same question for Indians. Indians have used copperware to prepare milk for babies for thousands of years. Evidently, thousands of years of practice only means thousands of years of unfortunate mistakes, and countless of unnecessary loss of lives. People often are stuck with an old practice or an old belief and they are emotionally attached to it.

                          1. re: Chemicalkinetics

                            It is notable that the title of the second article cited (occupying less than one page of text) ends with a question mark. This is a whopping sample of two children, raised separately in a highly polluted country. The ICC in the one child is *speculated* to have occurred from the practice of BOILING AND STORING cow's milk for 6 hours) in bare copper--and this was the infant's ONLY food for the first 10 months of life! If you look at the data carefully, the increased copper level between the milk boiled in the bare copper pan and the SS one was 0.51 mg/L (EPA safe WATER limit = 1.3mg/L)

                            No one here has ever recommended such an extreme diet, prepared and stored in bare copper. What was done to this infant is the equivalent of feeding it only Zambaglione through its entire infancy and development. Unrealistic in the extreme to generalize anything from this.

                            The earth-shattering conclusion: "We conclude that the method of feeding may increase the copper intake and cause ICC [of one child]." Duh, ya think?

                            1. re: kaleokahu

                              <It is notable that the title of the second article cited (occupying less than one page of text) ends with a question mark>

                              True, but I believe it was one of the earlier articles. When you are the first dude trying to say something profound, you tend to be conservative/reserve. Since then, it has been largely aceepted that copper was the major cause for ICC in India. I don't think people doubt that anymore. What we know for sure is that since the elimination of copper cookware for preparing milk for children, ICC, which was common and very lethal, has been largely eliminated, which is a very good thing.

                              <the increased copper level between the milk boiled in the bare copper pan and the SS one was 0.51 mg/L>

                              Yes, but the total is already close to 1 mg/mL, and once you start to store for three hours (not at boiling temperature), then it shoots above 2 mg/mL. This means if someone is going make a slow pot roasting in an unlined copper cookware (a few hours), one can easily get above 1 mg/mL. Keep in mind that milk is actually basic, while tomato, vinegar or wine ...etc are acidic. In other words, the copper leaching into acidic soups is expected to be higher than that of the milk (basic). It isn't that difficult to get above 1 mg/mL of copper for acidic solutions at an elevated temperature. Also keep in mind that an adult and an infact have different tolerance. You may consume >1 mg/mL and be fine, but it is probably not a good idea for an child or a senior. Our clearnce ability changes as we age. In addition, you may only have acute toxic effects like throwing up, while a child may have chronic effects like liver damage. Chronic toxic effect is a lot more messy.

                              <"We conclude that the method of feeding may increase the copper intake and cause ICC [of one child]." Duh, ya think?>

                              Actually, it was a suprising finding for many, including me, which was why that 1982 article was very conservative in its language. You know Wilson's diease, right? Let's say you have Wilson's diease. Copper consumption can easily cause toxic effects for you. You may get sick from consumption of copper, and you may even die. However, copper does not CAUSE Wilson's diease for you. You either had it since birth or you don't. Copper may kill you, but it does not CAUSE Wilson's diease. ICC is different. It is now believed that high consumption of copper can literally cause/trigger a health child to have ICC.

                              1. re: Chemicalkinetics

                                Right, milk (pH 6.5-6.7) is a base.

                                If this "fact" and that 2-person "study" using an infant who ONLY ingested cow's milk boiled and stored in bare copper in a highly polluted country is any indication of the merits of this debate, we should stop wetting ourselves. It's not a lot different than saying Food Processors are dangerous because nut residue can build up in them and put a person who is allergic into shock.

                                Many daily multivitamins contain up to 3mg, and for good reason--most Americans are deficient. According to the Mayo Clinic newborns to age 3 SHOULD ingest 0.4 to 1mg of copper daily for good health. This ramps up to 2mg by age 10, and up to 3mg/day for adolescents and adult females. See,

                                But what does Mayo know? Nut residue indeed.

                                1. re: kaleokahu

                                  <If this "fact" and that 2-person "study" >

                                  Fine, milk is mildly acidic, but definitely not as acidic as many of the soup ingredients, like wine or tomatoe or vinegar...etc. Boiling milk and then let it cools down and sit at room temperature for 3 hour is certainly not as bad as slow cooking in tomato juice or vinegar based soup at a elevated temperature for long duration. In the big picture, my original point about boiling milk and cool down for 3 hours is certainly on the mild side of all situations.

                                  It is definitely not just a 2-person study. It is just one of the first definite study. The elimination of copper vessels for milk has largely responsible for the termination of ICC is the bigger evidence. ICC is definitely nothing like nut allergy.

                                  <Many daily multivitamins contain up to 3mg, and for good reason>

                                  Many copper cookware are lined for good reason too because it is very difficult to control the amount of copper leaching into the foods. I seriously doubt Mayo Clinic would condon people to cook with bare copper cookware. It is only saying that for people who cannot get copper in their diet that they can acquire through a controlled dosage. That Mayo page also indicates that there is no real RDA or RNI for copper.

                                  Copper can come from many forms, but not all are the same. 1 mg of copper from avacado is not the same as 1 mg of dissolved copper from cookware or water pipe. G. Brewer from U of Michgan Medical School has pointed to this in his article: "The Risks of Copper Toxicity Contributing to Cognitive Decline in the Aging Population and to Alzheimer's Disease"


                                  Quote: "Copper in food is bound to organic molecules that are taken up by the liver, and the copper is processed and safely bound to molecules such as copper chaperones. However, the evidence is that much of inorganic copper that is ingested bypasses"

                                  "We only occasionally found levels exceeding the EPA limit of 1.3 ppm, but about 20% of the time found levels exceeding the levels (0.12 ppm) causing AD type brain damage and loss of cognition in the AD model studies of Sparks and colleagues "
                                  (this agree with the German researcher finding which stated that "We found that the disease can even be caused by copper concentrations below the allowed concentration given by the German Guidelines for Drinking Water ").

                                  "These preparations often contain as much as 2.0 mg of copper ... even though it has been clearly shown over the last 15 years or so that the real figure is about 1.0 mg per day. The reason for including any copper at all in these supplements is not based upon data, because copper deficiency is extremely rare. It is probably based upon some concept of “completeness” in terms of including all essential vitamins and minerals. However, it turns out , it is a mistake to include copper. "

                                  If you want to recommend people to cook with bare copper cookware, go ahead. I am not going to that .

                                  1. re: Chemicalkinetics

                                    I'm not recommending that anyone cook in bare copper for infants or those who already ingest 'way too much copper. I'm not even recommending that healthy people use it much. What I *am* saying, is that the perils of doing either are drastically overblown, as Italy and France have proven for centuries.

                                    When it comes to ways to reduce already high total intake into the nominal range, eschewing bare copper for those individuals makes sense. Especially in places, like India and Pakistan, where eliminating the *major* contrubutors, like consuming nuts (about 14mg/kg), spices (about 7mg/kg) and polluted water in the food chain, would not be feasible. Also contributing to the problem in those countries is the lack of mineral and antioxidant/chelate *balance* in the diet to normalize metabolism and elimination of what copper the people *do* ingest. Not to mention the lack of Pasteurization, refrigeration and other factors that would obviate the need to boil milk at all. Or pesticides and fungicidesthat enter the food chain. Or the strong correlation of ICC to parental consanguinuity and strong genetic component.

                                    The "study" we have been discussing was indeed a 2-person study, or more accurately a 1-person *anecdote*. We know nothing about what that one sick child's environment was like. On the other hand we *do* know that over 150 million Americans have bare copper pipes supplying their potable water, many of whom take multivitamins containing additional milligram quantities of it, and yet most Americans are deficient in copper. Cases of copper toxicity other than in India have always been highly uncommon.

                                    The bottom line is that there is no proof that ingestion of copper at the rate of 2mg per day is toxic. In fact, for adults, that intake level is RECOMMENDED by the World Health Organization. See, World Health Organization. Trace elements in human nutrition; a report of a WHO Expert Committee. WHO Technical Report Series 532, Geneva. p. 70 (1973). In fact, WHO recommends that infants get nearly three times MORE copper (80 µg/kg body weight per day) than adults (30 µg/kg body weight per day).

                                    On the other hand, for adults at least, daily intake of less than ONE mg/day day dangerously increases the risk of heart attack, severe tachycardia, and extrasystolic beats. According to the Canadian government, daily copper intake of FIFTEEN mg/day is generally recognized as nontoxic. See,

                                    The third study cited (the only one not written by the team claiming to have eradicated ICC) does not exactly support the case for a causal connection: "However, it is less clear whether an excessive intake of copper alone is sufficient to cause ICC... Two competing theories ...If copper acts in synergy with a plant, fungal, or other biocidal toxin... both a genetic vulnerability and an environmental challenge,
                                    then the putative gene must be identified.
                                    Finally, given that infantile copper toxicosis may have a
                                    genetic component to its causation, and older children with non-
                                    Wilsonian copper-associated cirrhosis may have an as yet
                                    uncharacterized genetic disorder, DNA from these patients and
                                    their families should be collected and stored for possible future

                                    You might know... How many milligrams of copper are in a liter of solution at the concentration of 98 µmol/L?

                                    1. re: kaleokahu

                                      < Italy and France have proven for centuries>

                                      How did they prove it? All we know is that people are not dying left and right. There is a huge gray area between "dying left and right" and "completely healthy", for example chronic dieases as one. Indians was using copper vessels to prepare milk for infants for thousands of years, and certainly the babies were not dying left and right and most survived -- just the fact that Indian has a huge population and fast population growth proves that you can have a toxic practice and still overcome it with shear birth rate.

                                      You of all people should understand this considering that you are concern of Teflon cookware. We don't have people dying left and right from Teflon cookware. In fact, there isn't a good solid study of Teflon causing any death at all, while there are plenty case studies for copper does.

                                      <The "study" we have been discussing was indeed a 2-person study, or more accurately a 1-person *anecdote*. >

                                      That particular study was. What I was saying is that there were more than just this study.

                                      <most Americans are deficient in copper>

                                      I definitely won't say that. True copper deficiency is extremely rare. Yes, it is true that many Americans have lower level of copper than the so called recommended level, but if you truely look at people who are so low to show toxic effects -- that is really low.

                                      <In fact, for adults, that intake level is RECOMMENDED by the World Health Organization>

                                      That is a very old recommendation and there was no solid reason for that recommendation. It was so old that ICC wasn't even linked directly to copper at the time. I mean. That recommendation was made at a time where boiling baby milk in copper vessel was considered acceptable.

                                      <daily copper intake of FIFTEEN mg/day is generally recognized as nontoxic>

                                      From the link, I actually read that "Ingestion of more than 15 mg of copper has been reported to be toxic to humans". In addition, it cites a very old paper from 1975 and it was referring to acute toxic effect. In fact, once you ingest more than 15 mg, then you are likely to have acute toxic effects. The cited article states that "The ingestion of more than 15 mg of elemental copper usually produces nausea, vomiting, diarrhea, and intestinal cramps. In more severe cases, intravascular hemolysis is seen." Yet, plenty other people get acute toxic well below this level. This is just the level where MOST people will get acutely sick. Many people will get sick at a level lower than this.


                                      The level for chronic effects are usually even lower. Think mercucy. Published in Clinical Toxicology. A man accidentially drank 3 kg of metallic mercury and lived. Yes, 3 kg!. He certainly cannot do that in long term.


                                      The amount of element requiref to give a chronic toxicity is much lower than acute. So if we know that MOST people get acutely sick after 15 mg of copper, then we almost certainly know the toxicity level for chronic level is much lower.

                                      Anyway, my bottomline is that copper is an essential element, but most people acquire enough copper from foods. Even if they do need more copper nutrients, the last thing to do is to use a bare copper cookware. I would recommend copper rich food or copper supplements over exposed copper cookware. If you want to use a copper frying pan once awhile, that is probably fine. Copper stock pot for making soup... not happy with that idea.

                                      Copper has a molecular weight of 63.5 g/mol, so 98 µmol is the same as 98 µmol X 63.5 g/mol = 6223 µg or 6.2 mg. So 6.2 mg/L.

                                      1. re: Chemicalkinetics

                                        OK, you know better than the World Health Organization.

                                        As the studies you cite make evident, there isn't even a baseline of the incidence of ICC with which to compare the statistics. Does it bother your scientific sense that the reported 69% decrease in the use of brass pans didn't leave 31 or so % in ICC cases, but rather a virtual elimination of reported ICC?

                                        My strong hunch is that there is, in this population in India, a genetic predisposition to either storing copper, inability to excrete it, or both. But I'm glad if this population cutting back to below levels that are nontoxic for most of the rest of the world has helped them.

                                        1. re: kaleokahu

                                          <Ok, you know better than the World Health Organization.>

                                          First this kind of argument is not helping. If we have to go down this road, then I can also say that "Ok, you know better than G. Brewer from Univeristy of Michgan Medical School "

                                          <My strong hunch is that there is, in this population in India, a genetic predisposition to either storing copper, inability to excrete it, or both>

                                          That is a fine theory and certainly there is a good possibility of it. The important point is that ICC is not like Wilson's diease. Wilson's diease occurs on a pure genetic level alone. You can eat copper or not eat copper in your whole life. It won't affect your chance of hainvg Wilson's disease. Copper consumption may kill a Wilson's diease person, but copper does not cause Wilason's diease. ICC is different. It may be partial genetic (not sure), but it occurs when high level of copper is ingested at a young age. Obviously not every children get ICC. Otherwise, India won't have a huge population since ancient time.

                                          Nevertheless, one can say the same for many things too, right? Not every smokers get lung cancer, not everyone exposed to lead get lead poisoning, and not every alcoholic get liver failures.

                                          Here is a soft article on smoking and gene and lung cancer. Quote:

                                          "Scientists have identified genetic variants that increase a person's risk of developing lung cancer, but only if they have ever smoked. The findings will shed light on how people get addicted to tobacco and how our genes and environment conspire to cause cancer."

                                          "People who smoke and who carry one copy of each genetic variant increase their risk of lung cancer by 28%. Those who smoke and have two copies of each variant increase their risk by 80%. However, people who carry the variants but who have never smoked are not at any increased risk of the disease."

                                          Nevertheless, we still contribute tobacco smoking as a cause for lung cancer of these people.


                                          1. re: Chemicalkinetics

                                            The difference is you: dissed WHO (and Mayo and EPA, among others) for stating *current* recommended and toxic intake levels with which you disagree. I am in agreement with Professor Brewer; I take issue with your generalizations concerning ICC and the implications you lay about it about people outside India.

                                            There are 'way too many variables here to make those leaps to cooking in unlined copper is unsafe. For instance, there are no fewer than *eleven" other minerals in water that directly and substantially affect copper uptake, and many that do the same within the body.

                                            Is there TCC (Turkey), BCC (Bedouin), NCC (Nepalese), etc,-CC?

                                            1. re: kaleokahu

                                              Professor Brewer and others are in disagreement with what you stated for the level of WHO and Mayo. Brewer stated that 1 mg is probably as high as it should ever go and that supplement of copper in inorganic forms has bad effects (such as cookware or waterpipe or pills). Brewer and the German researchers indicated that toxicity cases were found below the recommended level.

                                              <dissed WHO (and Mayo and EPA, among others) for stating *current* recommended and toxic intake levels >

                                              In that case, I take issue that you consider unlined copper cookware is safe. None of these organizations have ever agreed unlined copper cookware usage in the first place. You are extrapolating things which none of these organizations have ever said.

                                              <I take issue with your generalizations concerning ICC and the implications you lay about it about people outside India.>

                                              No, you asked the question if there are actual cases of copper poisoning from cookware. "...we ought to be given some *actual* cases of it happening" Yes, there were. Thousand of ICC cases. All I have to show is one case, but I have shown thousands, and that alone is enough to show there in fact copper cookware can cause toxic effects. Now, you are asking why not more. So what if I can show more cases? Are you going to be suddenly convinced? I don't think so.

                                              <There are 'way too many variables here to make those leaps to cooking in unlined copper is unsafe.>

                                              There certainly aren't any evidence that cooking in unlined copper cookware for long period of time is safe. You are trying to have it both way. On one hand, you want to argue that copper cookware is safe by citing high end copper intake. For example, you argued that "daily copper intake of FIFTEEN mg/day is generally recognized as nontoxic" Well, I didn't see that in your cited article. What I read is that this is where most people would have shown clear acute toxicity. Some people will show at a level lower than "most people" and many chronic toxicity will show up way below the acute toxic level.

                                              On the other hand, you are also trying to say "I'm not even recommending that healthy people use it much." Take a stance. I have. My stance is that I am against recommending bare copper cookware. So are you for or against? If you are for recommending people in general to use bare copper cookware, then fine, state it clearly. If you are against, then I have no idea what you are arguing. You cannot keep on arguing that bare copper cookware is safe and then say "Well, I am not recommending". You don't seem to able to convince yourself. How are you going to convince others?

                  2. re: huoguofengzi

                    Hi again, huoguofengzi:

                    Just thought you should know that the US Environmental Protection Agency allows 1.3mg/liter copper concentrations in drinking water. See, Federal Register / Vol. 65, No. 8 / Wednesday, January 12, 2000 / Rules and Regulations. pp. 1976. Significantly, this limit is based on an actuarial LIFETIME of consuming and bathing in water at that level without ANY gastrointestinal effect, and takes into account all other dietary sources. If you're interested in a balanced assessment of the good and bad effects of copper intake, as well as a decent picture of where most Americans are (marginally to moderately LOW), see Notable among the effects of chronic copper deficiency is increased incidence of lipid (cholesterol) problems and heart disease and glucose intolerance.

                    I'm not aware that anyone has ever actually tested unlined copper cookware to determine how much copper a pot of polenta or fruit jam supplies per serving. But I bet it is substantially below 1mg/serving.


                    1. re: kaleokahu

                      Thanks so much, kaleokahu for both of your very informative and helpful replies! Now I'm curious about these copper woks and how they're used too. Most cooking in Kashgar (an ethnically "non-Chinese" region of China, more similar in many ways to the various adjacent -stan countries) isn't done in woks, and so most of the copper pots made and sold there are not woks - although lots of woks are available too. Now I wonder if the woks are aimed more at the Chinese tourist market rather than local Uyghur customers...hmmm...I'll have to look into this when I go out there again in July. I'll report back!

                      1. re: huoguofengzi

                        Reading through this entire thread I was most curious about how these woks were most commonly used - if they were intended for preparing some specific dish... What did you find?

                  3. I chalk it up to a poor idea at the time, but sure is pretty. If it is indeed copper you really should not cook in it. The only thing I will expose to plain untinned copper is egg whites. If you are hand beating them you do get superior loft. Other foodstuffs should not come in direct contact with copper.

                    1 Reply
                    1. re: Candy

                      Hi, Candy:

                      IYO, does that extend to sugar pans, preserve/apple butter pans, polenta pans and zambaglione bowls?