I wrapped copper tape around a wood stick:
I will use this stick to push any buttons in public and press door handles. How reasonable is it to touch the copper-coated stick after it touching potentially contaminated surfaces? Do I have to pay attention to not touch the stick at places where it touches other surfaces?
Here's a study using a different coronavirus.
Brasses containing at least 70% copper were very effective at inactivating HuCoV-229E (Fig. 2A), and the rate of inactivation was directly proportional to the percentage of copper. Approximately 103 PFU in a simulated wet-droplet contamination (20 µl per cm2) was inactivated in less than 60 min. Analysis of the early contact time points revealed a lag in inactivation of approximately 10 min followed by very rapid loss of infectivity (Fig. 2B).
From the Justified Advice Thread Summary
An important update for me was that the halflife on copper is ~3.5 hours, which means that it's actually quite awhile before copper will kill coronavirus thoroughly enough to be "safe". I think it's more useful as something that "becomes clean overnight" than something like "you can reliably use a copper thing without having to clean it."
This was the clear winner of JPA Olympics– it’s cheap, effective, and very few people had heard of it before. In fact we were hoping for a highly polished, intensely researched post on just this; unfortunately no one has the time right now.
In its place, please enjoy these links:
- This pre-print showed that this coronavirus in particular had a half life of 2.4-5.11 hours on copper, in contrast to 10.5-16.1 on steel or 13-19.2 on plastic
- This review showed H1N1 decreased by 4 logs (a factor of 10^4) in 6 hours;
- This study showed vaccinia and monkeypox viruses reduced by 6 logs (a factor of 10^6) in 3 minutes
- This study showed murine norovirus was destroyed in 30 minutes, though it doesn't work very well at 4C;
- This review says that copper oxide filters neutralize all of "bacteriophages [58-62], Infectious Bronchitis Virus [63], Poliovirus [61,64], Junin Virus [59], Herpes Simplex Virus [58,59], Human Immunodeficiency Virus Type 1 (HIV-1) [11,65-67], West Nile Virus [11], Coxsackie Virus Types B2 & B4, Echovirus 4 and Simian Rotavirus SA11 [68]. More recently, the inactivation of Influenza A [55,65], Rhinovirus 2, Yellow Fever, Measles, Respiratory Syncytial Virus, Parainfluenza 3, Punta Toro, Pichinde, Adenovirus Type 1, Cytomegalovirus, and Vaccinia [65]".
The basic answer is - pretty fast, but not immediately.
This paper compares 9 metals (lead kills slightly better than copper but that unfortunately extends to the humans; zinc and some other metals also kill pretty well, only two did not). Within an hour, copper dropped CFU from 10^6->10^1 (the measurement threshold). Zinc took 2 hours, nickel 4.
(this research actually done by Connor Flexman)
Your stick would be significantly better if you used a uniform cylinder, rather than a piece of natural wood. The uneven shape means that the copper tape has a lot of crevasses, which can get dirt in them that's hard to clean out. If the copper has dirt on top of it, it's not going to inactivate anything that's on top of the dirt.
Relevant section:
...In an experiment with aerosolized SARS-CoV-2 and SARS-CoV-1, at 21-23 degrees C and 40% humidity, both reached undetectable levels within 8 hours exposure to copper; by contrast, they lasted 72 hours on stainless steel and plastic.[1]
H1N1 influenza, which was another pandemic virus, though not a coronavirus, lasted significantly less time on copper than stainless steel; 10^5 viable viruses after 24 hours on stainless steel vs. 10^2 viable viruses after 2 hours on copper.[2]
Human coronavirus 229E remains infectious on plastic, ceramic, glas
Disclaimer: I'm not an expert.
It seems to me that this preprint suggests that in certain conditions the half-life of HCoV-19 (SARS-CoV-2) is ~0.4 hours on copper, ~3.5 hours on cardboard, ~5.5 hours on steel, and ~7 hours on plastic.
If you haven't done so already, I recommend choosing and marking which end is to be held. If one end is for poking potentially contaminated surfaces, and the other is for holding, then contact seems like less of a concern. (Although I can't tell how long it is from the picture, and I'm not sure how big of a factor that is.)
Small observation. There are a lot of nooks and crannies in the foil. Will that perhaps allow a layer of "insulating" stuff to build up that would then protect the virus from the affects of the copper?
If so gloves might just be a better solutions -- or taking more time to wrap the stick to achieve a smooth surface. (Or just go buy a 8" or foot long section of cooper pipe/tube.)
Just had a thought too. Anyone know what the oxidation process on the copper will to here? Will that reduce the effects?
It's not either gloves or the copper-stick. You can use both to have more layers of defense.
The original post seems like an off-the-cuff question that was a bit oddly specific. I think it'd be nice if it got refactored a bit to be useful to newcomers trying to get a handle on "how useful is this copper thing?", with examples about what sort of considerations you might look into.
Afaic if you use it more than once every few hours, you're better off just using a different knuckle for each button, taking care not to brush them against pockets or the like. When you run out of knuckles, wash or disinfect.
That paper only looks at bacteria and does not knowably carry over to viruses.