Should we all switch to copper?
November 2, 2011 5:27 PM   Subscribe

If copper is so effective at destroying bacteria, including antibiotic resistant organisms and viruses, why don't we see it used as a standard material in settings like hospitals, schools, public transportation etc?

There has been a number of trials recently in hospitals across North America, the UK and Japan where it was identified that copper is an active antimicrobial agent that actually destroys micro organisms. It does this by punching holes in the surface of the organism and then destroying enzymes so the organisms can't replicate (very lay person interpretation) If you want to learn more you can look at this antimicrobial copper website From what I've seen there is not a big difference in price between stainless steel and copper in terms of prices for items such as door knobs, push plates, over bed tables etc. Please shed a little light on why this copper isn't used more? If you can provide links or other scientific information that would be great.
posted by YukonQuirm to Science & Nature (21 answers total) 7 users marked this as a favorite
Because it costs about 10x as much.
posted by tchemgrrl at 5:39 PM on November 2, 2011 [4 favorites]

I don't know much about the antimicrobial properties of copper, but I don't think you're right about the pricing. By my calculation, copper is around 50 times as expensive as stainless steel by volume. Here are the figures I used:

Current price of copper: $3.60 per pound
Density of copper: 8.94 grams / cm^3

Current price of stainless steel: $0.0839 per pound
Density of steel: 7.85 grams / cm^3

Someone else can come along and figure out how much copper plating you'd need in a hospital to make a difference, and how much that would run compared to stainless surfaces, but I bet it's not nothing.
posted by Salvor Hardin at 5:43 PM on November 2, 2011 [2 favorites]

Copper quickly tarnishes, and requires lots of cleaning (unless it's covered with a clear coat, which would probably negate the health effects.) Stainless just needs a quick wipe to keep it clean.
posted by Marky at 5:49 PM on November 2, 2011 [3 favorites]

Copper is much more expensive than stainless steel. People steal copper from construction sites all the time. Not so for stainless steel.

So that would be a major contributing factor to why copper is not used more widely.
posted by dfriedman at 6:00 PM on November 2, 2011 [3 favorites]

In any event, in spite of the cost, what you're suggesting does seem to be done.

See also this discussion of its antimicrobial properties from Wikipedia.
posted by dfriedman at 6:06 PM on November 2, 2011

Response by poster: Just to clarify, I have done a bit of looking around and cost does not seem to be the driving factor for limiting the use of copper. Yes, the base price may be considerably more for copper then stainless but for actual door knobs or push plate there doesn't appear to be a big premium - check out this article that quotes:

"Ironically, stainless steel is actually more expensive than steel coated with brass ­ $117 vs. $108 for the hardware for one door, according to one price quotation."
posted by YukonQuirm at 6:07 PM on November 2, 2011

Response by poster: Also, we need to remember the cost of health care acquired infections in hospitals. A CDC article quotes the following:

"With an incidence of approximately 4.5 HAIs for every 100 hospital admissions, the annual direct costs on the healthcare system were estimated to be $4.5 billion in 1992 dollars.[1] Adjusting for the rate of inflation using the CPI for all urban consumers, this estimate is approximately $6.65 billion in 2007 dollars."

What I'm looking for is reasons why copper might be a bad choice. I can't find literature that makes the antimicrobial properties and studies done to be inadequate - but there must be something out there...right???
posted by YukonQuirm at 6:12 PM on November 2, 2011

Based on my limited knowledge, I'd also wager that hospitals have policies specifying the level of cleanliness/sterility for many (I hesitate to say all) procedures and when they are followed (aka not all of the time) infection control is, well, under control. Hospitals are well-oiled and highly regulated machines. That over-bed table can turn into a sterile field when the need arises, and if the rest of the time the housekeeping staff follow their guidelines and the nursing staff follow their guidelines, the table will remain clean.
Sure, if surfaces were replaced with copper than they might be "cleaner", but I can't see why hospitals are the best market for that. Public areas could benefit from cleaner surfaces, hospitals could benefit from more staff on hand to follow the procedures.

(take this all with a grain of salt, I'm about eleven weeks into nursing school.)
posted by pintapicasso at 6:20 PM on November 2, 2011

Well probably not a big concern in a lot of applications but copper (and most other native metals) can be really harmful to a lot fish in fairly low concentrations. I believe it destroys their sense of smell. However they do a great job of keeping moss off roofs and killing algae (copper and zinc are often used on roofs in the pacific northwest for just this purpose).
posted by bartonlong at 6:22 PM on November 2, 2011

Also, we need to remember the cost of health care acquired infections in hospitals.

I believe that figure includes all infections, not just those on surgical sites. So you're conflating infections from catheters, MRSA infections, pneumonia, etc. So it's questionable whether copper instruments would help a significant number of the cases in your example.

And even those on surgical sites are usually not caused by dirty instruments - more frequently the microbes are simply in the environment, on the patient's skin, etc. So using copper instruments to prevent infections is probably not an effective method of preventing infections since the bugs from the patient's skin are probably a bigger threat.

Moreover, just because it's a good idea doesn't mean it would get done. Someone has to pay for this. Hospitals aren't going to pay for it - they're already budgeted right down to the dollar and they frequently get paid more when a patient suffers complications (talk about bad incentives). The US healthcare system is notorious for avoiding preventive solutions and paying for it down the line. For instance, aggressively helping patients manage diabetes saves a ton of money in ED visits and admissions, but instead we hang patients out to dry until they show up at the hospital with critical blood sugar levels and then we pay for their massively expensive ED / inpatient care. Pretending that switching to copper would actually prevent infections, which is not well-established, if Medicare or a state's Medicaid program were considering paying for this all it would take is for a steel instrument manufacturer to raise a ruckus and call a few congressmen and the program that aims to save money with an initial investment would get labeled "government waste."
posted by Tehhund at 6:49 PM on November 2, 2011

Best answer: Pubmed is your friend. I would be weary of a site extolling the values of copper coming from the "International Copper Association."

A starting point for your literature search--a review article from 2011: Metallic copper as an antimicrobial surface.
posted by scalespace at 7:08 PM on November 2, 2011 [1 favorite]

Could it just be that silver caught on first--and that sneaky copper barons want a piece of silver's antimicrobial pie? Even Curad is apparently using silver in bandages now.
posted by mittens at 7:14 PM on November 2, 2011

It is the price. Copper costs 10x the price now - BUT add in the extra demand if copper replaced stainless steel. The demand would sky-rocket, supply is the same, and the price would be 100x more expensive than now.

Copper is one of the most important elements on Earth. It is an amazing material that has revolutionized and modernized all our lives. Much more important than copper's ability to kill bacteria is its ability to conduct electricity. It is highly malleable, and can be easily formed into wire. And, it is fantastic at conducting electricity, the voltage drop over long runs of wire is minimal (at least compared to other elements).

There already exists a huge demand for copper - and price just keeps going up and up, like gold or oil. If copper replaced stainless steel, with the extra demand, the price would explode. Keep in mind, to operate as a modern facility at all, the hospital already made a massive investment in copper, maybe $100,000 US for a medium sized hospital - all in copper wire, just to power up all the fancy modern gadgets.

Lots of thing can kill bacteria a whole lot cheaper than copper.
posted by Flood at 7:14 PM on November 2, 2011 [4 favorites]

Best answer: It can't replace certain metals due to hardness and wear.

I thought of this as a former Jeweller. Clients, when deciding about whether to pay the premium for platinum over white gold, would need to know more about each metal due to misunderstandings about how the noble metals work. They would say "But I heard platinum is softer - it will scratch!" and I would counter "But it is more dense - it will take a finer network of scratches. And it is naturally white, because it is more pure in jewellery form - and if it's an alloy, it's two of the platinum metals, so the scratches will be the same colour as the surrounding area, and it will develop a nicer patina over time. White gold is harder, but it will only show the bigger scratches without the smaller ones to blend with them; the platinum plating will wear and scratch off and it will be yellowish underneath. To reapply the platinum plating, the entire ring needs to be buffed and you will lose metal."

So, with copper, in the case of being hygienic for hospitals and food surfaces, for example, it is softer and while corrosion-resistant, when exposed to water and other environmental issues, the verdigris that forms has poisonous compounds and needs to be removed with an acidic cleaner or physical effort (I use a cut lemon and salt, or ketchup, on my copper-bottomed pots, and jewellery).

And the other problem with that is wear - scratches and dings, especially from the need for abrasive cleaning would mean that unless they are well-cleaned and de-greased to the bare, smooth, polished metal, you have places for bacteria to hide. Even if the copper would is an "antimicrobial agent", bacteria can grow on gunk sitting on it - even on a greasy fingerprint. To get the strength and hardness of stainless with copper, you would not be using the same amount of metal - it would have to be thicker and perhaps alloyed, and that's when you have to factor the price in again and it would no longer possibly be pure enough to have those magical factors.
posted by peagood at 7:51 PM on November 2, 2011 [14 favorites]

Copper is reactive and will degrade.

Stainless can be cleaned with bleach/harsh abrasives/heat and pressure (autoclave); you can clean stainless steel with much harsher sterilization methods than you can with copper (without whatever you're cleaning wearing away unduly quickly). Stainless steel is also much much harder and resistant to damage.

Hospital cleaning protocols are all written around the cleaning of stainless steel. Those protocols may not be adequate for copper, or be damaging to the same objects made from copper.

The antimicrobial properties of copper (and silver) just aren't robust enough to be worth replacing everything stainless steel with copper.

There is continual research on improving hospital practices to save lives/reduce infections/prevent microbial resistance to sterilization. If increasing the use of copper is beneficial, you'd see a lot more copper used in hospitals.

Then again, there's copper toxicity.
posted by porpoise at 8:26 PM on November 2, 2011 [5 favorites]

It sounds like a good idea. Good ideas are everywhere, but somebody has to do a ton of research on the consequences of making any change to hospital standards, and somebody has to start a company that makes copper goods to the right specifications, and market them, etc. The government is the traditional research funder, but maybe not in these times of cutbacks. Entrepreneurs are the people who start companies with new ideas.
posted by theora55 at 7:19 AM on November 3, 2011 [1 favorite]

OP: Just to clarify, I have done a bit of looking around and cost does not seem to be the driving factor for limiting the use of copper. Yes, the base price may be considerably more for copper then stainless but for actual door knobs or push plate there doesn't appear to be a big premium - check out this article that quotes:

"Ironically, stainless steel is actually more expensive than steel coated with brass ­

Brass <> copper. Brass prices are lower than pure copper prices. And brass does not necessarily convey the same antimicrobial properties as copper.

But it's still very high maintenance, if one wants to avoid tarnishing (and hospitals would). The only exception is coated brass, which means the microbes will have a protective barrier between them and the brass...
posted by IAmBroom at 9:03 AM on November 3, 2011 [1 favorite]

(Sorry - "<>" means "is not equal to". I just realized that could be misconstrued as "<>", "equal either way".)
posted by IAmBroom at 9:05 AM on November 3, 2011

It'd be interesting if a brass with enough copper would suffice. This study [PDF] seems to suggest it has been researched. My first "job" was as a brass polisher on the Lightship Nantucket, which was a sailing museum at the time. Apparently they're still used on cruises, so there's existing infrastructure for knowledge transfer at least.

The common wisdom at the the time was just to put your arm into it, using a rag of some kind. I was on the fence about buffing as opposed to hard pressure. Sometimes it worked, sometimes not. Direct exposure to sea air seemed to make buffing harder but that wasn't the only factor at play. I kept wondering about air currents in the ship. Anyway, I guess it was copper chloride (exposed, like on stairs next to exterior doors) vs. copper carbonate (filtered air, far from exterior doors), and/or dezincification vs. verdigris. Light dezinc might have been the hard stuff buffing didn't work on.

That, in sum, might be why it isn't done today. Upkeep on ships was a pain so people avoided it. Without sea air it might be a lot better though.
posted by jwells at 9:59 AM on November 3, 2011 [1 favorite]

Bacteria can kill people and copper can kill bacteria. I haven't seen any clear evidence that covering everything with copper in a hospital will actually prevent bacteria from causing harm. The antimicrobial copper people have some studies backing their claims but they have some failings. Aside from size the study participants and hospital staff weren't blinded. Maybe seeing all that shiny copper just reminded the nurses to wash their hands more often!
You need more hard evidence before investing heavily in all that copper.

Of course if this stuff really turns out to work, let me be the first to welcome our new copperclad (steamdriven?!) robotic nursing staff.
posted by abx1-se at 2:14 PM on November 3, 2011

Stainless is some good stuff. Once you deal with corrosion and reactivity, you'll appreciate its many fine characteristics over other metals.

Copper's nominal role of bactericide has to be counterbalanced against its drawbacks.

Materials get selected for optimization reasons, usually. One spec usually does not win the day in design choices.

My guess is that stainless wins because it is hard, stable, durable, non-reactive, attractive, strong. Copper is ductile, soft, reactive. In the places you'd want it for bactericide, you would want stainless for many other reasons.
posted by FauxScot at 4:06 AM on November 4, 2011

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