Toxic Lead & chrome in coffee makers & espresso machines?

A. Just came across the interesting thread. My tuppence worth:

- if you treat your machine with non-approved chemicals, you could cause all sorts of unwanted reactions, including damaging plating and ending up with harmful chemicals you drink long afterwards.

- coffee itself has all sorts of low-level heavy metals and given that espresso machines pass national food regulations, they aren't the problem. I'd either use tested coffee beans or vary my intake and not always drink from one region.

- some people worry about fungus in coffee and bacteria in espresso machines (water tanks and piping particularly). These are likely to be much more harmful -- and faster in their effect on you! Never drink (nearly) non-boiling water from a machine.

- and then there are all the effects of plastics (e.g., the pipes in your machines...) on our hormones.

- You can't win. Enjoy your coffee!

See: pubmed.ncbi.nlm.nih.gov/24340307

A. Bob, firstly, I would not recommend you drink anything that may contain dissolved nickel, but I'd not know if nickel is attacked by coffee; I would suspect not but perhaps someone else can shed light on that point.
Secondly, I am not sure where your lead comes from - brass is a mixture of copper and zinc.
Thirdly, your question about chromium; this metal is normally pretty non-reactive due to a tenacious surface oxide layer; this is simply why stainless steel doesn't appear to rust - the chromium oxide on its surface protects it. However, again, if it is attacked by your coffee, it may dissolve. I certainly wouldn't drink any liquid that contains flakes of any metal, as it can cause abrasions of the mouth and stomach. However, if it dissolves, the chromium metal will probably be just trivalent, although it could also be numerous other, less common, oxidation states, depending on the dissolving conditions. Personally I would not be concerned, because we all use stainless steel utensils and even drink out of stainless steel cups, so I would be pretty happy to think that normal coffee will not dissolve chromium metal.

A. Bob,
You are of course correct in saying that lead is added to some brasses. The amount is normally about 2-3% by weight and it is called "free machining brass". The lead acts as a dry lubricant and smears over the cutting surface. This is good for machining brass, but creates a problem if the brass is electroplated because instead of plating into copper or zinc, you are plating onto a possibly poorly adhering layer of lead. Ideally the lead should be removed by careful cleaning prior to plating, but it is not easy to do. Hence, it is best practise to use lead-free brass if you are going to electroplate the material.
Some manufacturers will plate brass or copper to either make it look pretty or perhaps to prevent corrosion. Generally copper does not corrode in water, although there are a few circumstances when that is not true, but for 99.9% of the time, we can assume copper does not corrode. Brass, however, is more likely to, due to attack of the zinc. So, plating can reduce attack if it acts as a barrier between the brass and the water. However, the plated parts will be subjected to thermal cycling between room temperature and 100 °C (or more if it is the element that is plated) and this could ultimately result in a delamination of the plated layers from the substrate. Consequently it is not a recommended good practise to plate such components. However, if we assume the substrate is copper or zinc, the most likely plating is nickel followed by chromium. Cheaper plating may just be nickel, but of the article is left in water for some considerable time and then allowed to dry off, the nickel will slowly turn green due to the formation of nickel salts. The time this takes depends on the water composition (tap water is not just pure H2O!). If the nickel is plated with chromium, it will remain shinier much longer.
As far as chromium is concerned, all chromium metal is Cr(0), that is it has no valence, or oxidation state. However, if it is attacked, or "oxidised" to make it dissolve, the resulting chromium salt will be either Cr(III) or some other oxidation state. Chromium can take on numerous oxidation states, but the most "unhealthy" is Cr(VI) or "hexavalent" chromium. These compounds are often seen as orange or yellow in colour. It must be stressed, if you have chromium as just the metal, you CANNOT have hexavalent chromium present.
Finally, I reiterate my comments about metal flakes, namely these should not be knowingly drunk, as they could damage the gastric tract. I would not be too concerned about your coffee attacking the chromium, as we have used stainless steel vessels and utensils of preparing food and beverages (including coffee)for many years and there has been no cited evidence of chromium poisoning from foods or drinks prepared with these tools.

A. If the chrome metal is coming off into the espresso you may have a problem since stomach acid is primarily hydrochloric acid and will oxidize it to hexavalent chrome. More likely however is the chrome is flaking when you are cleaning the portafilter. I would be more concerned regarding the lead leaching into your drinking water from the solder which was used to put the pipes together before the advent of lead free solder than from your espresso machine. Anything that is repeatedly heat cycled shouldn't be plated. All metals have different stiffness properties thus will eventually delaminate if they don't form an alloy at the point of contact which will cause migration of the base metal into and through the plating defeating the purpose of the plating.

A. Thanks for your participation and comments, Brian. But I do disagree with two things. Stomach acid will not oxidize the chrome metal to hexavalent chrome; the two pieces of evidence that I offer are the fact that chromium supplements would not be sold if ingesting them turned them hexavalent, and Topic 12044, one of the most enjoyable dialogs to grace our pages, where the proposition was tested.

I also cannot agree that parts that are repeatedly heat cycled should not be plated. Poor plating doesn't adhere well but good plating does. Molds for continuous steel casting are routinely nickel and/or chrome plated, and it's hard to imagine more extreme thermal cycling. Jet engine components are plated. And automobile brightwork (including the grills on virtually every car) routinely sees -30 F to above boiling temperature as it bakes in the sun, and it is virtually all copper-nickel-chrome plated.

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

A. I too would question Brian's assertion that stomach acid (hydrochloric acid) will oxidise chromium metal to hexavalent chromium. Hydrochloric acid is not normally considered an oxidising acid, so it would almost certainly only push the chromium metal up to Cr(III). To go all the way to Cr(VI) will take a powerful oxidising agent.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

A. Hi, Harley. Copper and zinc are not considered "food safe" surfaces. Chromium plating is, I believe, based on the fact that so many food surfaces have been chrome plated for so many decades. It is possible that the surface you are looking at is chrome plated, but possible that it is not. Why do you think it is, besides its shininess?

Regards,

A. CrIII and CrVI are nearly the only Cr redox forms seen in natural water or even waste water systems. CrVI is highly carcinogenic by inhalation. It is currently debatable whether it is toxic by ingestion. CrIII is a necessary human dietary nutrient. The EPA conducted a Toxicological Review on CrVI (1998) for safe drinking water limits. Most reports indicated that CrVI is primarily reduced to CrIII by saliva and acids of the stomach. If CrVI is able to pass these barriers (generally only at high doses) CrVI may cause liver and intestinal damage/cancers. The EPA is still investigating CrVI carcinogenic ingestion issues but has set the current drinking water standard at 100 ppb (0.1 mg/L). This is the current level which is considered safe to drink without any health risk for average consumption of water every day, over an average life span (~70years).

If your coffee has actually leached chromium from the maker (and the acidity of the coffee has not already reduced any CrVI to CrIII) it is highly unlikely that it has leached such a large enough concentration in your 12 oz drink to have any health risks.

A. Hi,
It is right the copper has a certain % of lead to make it manipulable for machining, therefore the Espresso machines exported to North America require the nickel plating to comply with the NSF rules; seems the lead from the boiler may be dissolved in the hot water that later will be used to brew your Espresso. In Europe it is not mandatory.

I have no idea about what will happen if you clean the boiler with Acid, and I don't know if it will affect the nickel in the boiler. Make it work for certain time, and make flow water through the group, and take the hot water to a local laboratory, and ask for the metals inside, and compare to the local water regulation for human drinking, if you are out of the parameters, try to get a boiler and pipes from a spare parts supplier.

A. Hi Marcio. Although having the parts electroplated is possible, tin "wiping' of copper pots and pans has been done for ages. In some countries traveling tradespeople apparently still offer the service to villagers.

But you can probably do it yourself if you wish and if you're reasonably handy. See topic 25553 and or topic 29192.
Luck & Regards,


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

A. Hi Mitch. I'd 1000 to 1, that it's not lead :-)
What makes you think it is?

Regards,

A. Hi Judie. I don't feign affection for California's Prop. 65 -- it would be a ridiculous waste of resources if it didn't do a 100X more harm than good, but it does :-(  
I bought a new gas stove last week plastered with warnings that kitchen stoves cause cancer. I bought a box of screws with warnings to immediately thoroughly scrub my hands if (horrors!) my fingers touched one. How do we alert mechanics to actual dangers while crying wolf a dozen times a day? I taught 'safety in metal finishing', and could not get across how dangerous hydrofluoric acid is because it has been drummed into employees that all acids are.

- - - - -
"The whole aim of practical politics is to keep the populace alarmed (and hence clamorous
to be led to safety) by menacing it with an endless series of hobgoblins" - H L Mencken
- - - - -

Unless you're living in a quite new home, your water probably runs through copper pipes which have leaded solder at every joint; there are lead water pipes in older neighborhoods -- but Prop. 65 has you focused on where your water is NOT picking up lead instead of where it may be :-)

Lead has long been used as one ingredient in solder for electronics to forestall the growth of "tin whiskers" which can short out and disable vital electronics, and as a minor alloying metal in brass screws and other brass components to make them machinable. One or both of those is where the lead is in your coffee machine.

There is danger everywhere, and reasonable people must work to balance "this" against "that" a hundred times a week -- but that is difficult when a toxic government that Mencken warned us about turns each molehill into a menacing mountain. Engineers are working hard to remove lead and other potentially harmful metals from designs, and I am completely confident that no water touches any lead in your Keurig coffee maker.

Regards,

A. Hi Robert. Tin will do it, and it can be electroplated in a shop, or "wiped on" by a handy D-I-Y'er.
Luck & Regards,


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

A. Hi Jay. Just guessing from the cost of materials and their functionality, I'd bet it's aluminum (which can leave those streaks). That's surely 1000X as likely as it being lead. I don't think you'll find much lead anywhere in modern appliances; but if you do, it would be in solder joints. To my knowledge nobody makes parts out of lead for home appliances nor plates them with lead.

I can't explain a lead reading from an unknown reviewer using an unknown protocol on an unknown object. If you're anxious about it , go ahead and get a lead test kit [lead test kits on eBay or Amazon] yourself.

Luck and Regards,

A. Hi Jay. Aluminum can do this, and people also worry about aluminum ... but that's a different subject covered by topic 8962, topic 17519, topic 22551 and others :-)

Regards,

A. Hi Joelle. I doubt that the company will write back because anything they say could be perceived as 'diluting the warning', which could expose them to government sanctions and increased responsibility in the event of a suit. It should be the state's job to tell you where this hexavalent chromium is since they claim it endangers you. But the warnings are not about safety, don't hold your breath waiting.

My guess is that the coffee does not touch hexavalent chromium, but that something aluminum or zinc plated in the innards or on the bottom of the unit has a hexavalent chromium conversion coating on it.

Regards,

  Thanks!