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There's a company called Norwex, started in Norway and now in other countries including Canada and the US, which claim its products "Clean without Chemicals":

Our line of cleaning products will save you time & money, improve health, and move towards creating a better environment. Norwex microfiber goes beyond "surface clean" with the innovative use of silver particles integrated into synthetic microfiber cloth ensure:

  • Single-celled micro-organisms such as bacteria, fungi, yeast, and viruses cannot survive or adapt in silver exposure
  • Surface-to-surface cross-contamination is eliminated
  • Rapidly drying cloths prevent bacteria growth in the cloth itself Cleaning with water only produces a healthy outcome for us and the environment.

Laboratory tests have proven that Norwex antibacterial microfiber reduced bacteria by 99.99% in 24 hours!

The company also mentions a research project related to its microfiber cloths:

Over the past year Norwex has been working with The Norwegian National Institute of Technology to establish a research project funded by the European Union in Brussels.

Are Norwex's claims true? Does the research project have any merit to satisfy those claims? And, perhaps too subjectively, would any harm come from exclusive use of Norwex's products (i.e., to the exclusion of traditional/popular chemicals)?

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    Highly effective against Vampire Bacteria
    – user5341
    May 24, 2011 at 19:32
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    While silver has known antibacterial properties, the inclusion of viruses in the single-celled list makes me... suspicious.
    – user5341
    May 24, 2011 at 19:36
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    The problem with this question is their definition of "chemical"; water is a chemical, for example - where do you draw the line when it comes to "without chemicals"?
    – Thomas O
    May 24, 2011 at 22:20
  • @Thomas O, I had the same thought, but let's assume that their use of "chemical" excludes water as they explicitly mention "cleaning with water". Can anyone give a less-strict definition of "chemical" so that we can get address the larger issue? Is there a commonly accepted colloquial definition of "chemical" that we can substitute?
    – Mike Christianson
    May 25, 2011 at 0:14
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    I followed the Norwex link you posted and found that it's one of those companies that make money by recruiting people who want to host parties at their own houses to introduce the product to potential customers. So although several of their claims might be scientifically sound, I would be careful in dealing with them -their sales method sort of rubs me in the wrong way.
    – Andy
    Jun 24, 2011 at 0:52

1 Answer 1

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Yes.

Summary:

There is evidence for both of the following claims:

  • Silver particle loaded fibers inhibit bacterial organism growth
  • Microfiber cloths are able to pick up a very large portion, if not all, of organisms on many different surfaces and under various levels of adherence to the surfaces

Thus, provided Norwex is using silver particles of the characteristics established to be effective by the available literature as well as a high-efficiency microfiber cloth as shown effective in the literature... then "Yes," their product will perform as described.

As the comments note, the antimicrobial properties of silver are well known, and there are several studies showing the beneficial performance of various polymeric fibers coated/loaded with silver particles in the nanometer range.

  • Chen/Chiang, "Preparation of cotton fibers with antibacterial silver nanoparticles," 2007 (SOURCE):

The surviving number of bacterium was about 550 after incubation...When the E. coli solution was sterilized with CFGI2/silver nanocomposite, the average number of surviving bacterium was less than 1.

  • Son et al. "Antimicrobial cellulose acetate nanofibers containing silver nanoparticles," 2006 (SOURCE):

In this study, the antimicrobial activity of the CA nanofibers containing Ag nanoparticles with an average size of 21 nm was tested against Gram-positive S. aureus and Gram-negative E. coli, K. pneumoniae and P. aeruginosa by the nonwoven fabric attachment method...When these bacteria were incubated on the CA nanofibers, no bacterial colonies were observed.

  • Lorenzi et al., "Biocide activity of microfiber mops with and without silver after contamination," 2011 (SOURCE):

The results obtained lead to the conclusion that silver microfiber mop was significantly more effective in reducing bacterial load despite initial high level contamination (106-107 CFU/50 cm2). Indeed, after low temperature washing, the bacterial load was already completely eliminated...

So, we have evidence for silver particles killing off bacteria by themselves, as well as a combination of fibers and silver particles in a product which has been shown to stunt bacterial growth. However, at least from what I can tell from the methodologies, they are examining the growth rate of bacteria once it has been added to the silver-containing material. In other words, these aren't wiping/cleaning tests for a contaminated surface; they're simply finding out if bacterial cultures grow on the material, and find that they don't.

So, what we need to know is whether or not microfibers are effective at collecting all bacteria from a surface. I don't think we can figure out exactly what type of microfiber Norwex is using, but there is some data on the efficacy of microfibers for cleaning:

  • Rutala et al., "Microbiologic evaluation of microfiber mops for surface disinfection," 2007 (SOURCE)

The microfiber system demonstrated superior microbial removal compared with cotton string mops when used with a detergent cleaner (95% vs 68%, respectively).

  • Diab-Elschahawi et al., "Evaluation of the decontamination efficacy of new and reprocessed microfiber cleaning cloth compared with other commonly used cleaning cloths in the hospital," 2009 (SOURCE):

New microfiber cloths achieved significantly higher decontamination for S aureus than new cotton cloths (P = .0012; regression coefficient = 1.0766), new sponge cloths (P = .001; regression coefficient = 1.0971), and disposable paper towels (P < .0001; regression coefficient = 1.5455) in wet condition.

However, this same study showed a negligible difference in removal once the various cloths had been washed 20 times. Unfortunately, I can't quite tell what the reduction was. The beginning contamination was 5 x 107 Colony Forming Units (CFU) per milliliter. The levels after cleaning are listed at around ~3-4 CFU... but I'm not sure if that really means it was taken from something in the 10s of millions down to 3-4.

  • Wren et al., "Removing bacteria from hospital surfaces: a laboratory comparison of ultramicrofibre and standard cloths," 2007 (SOURCE):

We showed that ultramicrofibre cloths consistently outperformed conventional cloths in their decontamination ability, across all surfaces, and irrespective of whether the bacteria were coated on to the surfaces with phosphate-buffered saline (PBS) or PBS containing horse serum to simulate real-life soiling.

In many cases, passage of UMF cloth over surfaces seeded with 2 × 106 organisms resulted in total bacterial removal.

So, I think we have seen evidence for both of the following claims:

  • Silver particle loaded fibers inhibit bacterial organism growth
  • Microfiber cloths are able to pick up a very large portion, if not all, of organisms on many different surfaces and under various levels of adherence to the surfaces

Thus, provided Norwex is using silver particles of the characteristics established to be effective by the available literature as well as a high-efficiency microfiber cloth as shown effective in the literature... then "Yes," their product will perform as described.

THIS blog states (unsure of where the claims are from, but seems to reference Norwex's site) that the bacteria are killed over a period of hours. This seems to track with the literature above, that silver kills by inhibiting further growth, not the immediate killing of organisms. Thus, it seems that some caution might be warranted, as there still may be live organisms on the cloth for a period of time after use and before they die off.

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    You also need to consider how the silver nanoparticles are bound to the cloth - it's entirely possible that the silver will be washed away with the first (or subsequent) wash(es).
    – Darwy
    Jul 9, 2012 at 1:57
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    @Darwy: One of the studies above says just that. After 20 washes there was negligible difference between the anti-microbial cloth and the cotton one, though I don't recall which particular anti-microbial product they were evaluation (this question is specifically about Norwex even though I tried to find information about the product family in general).
    – Hendy
    Jul 9, 2012 at 15:36
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    Keep in mind that silver is a heavy metal and when you wash or use the cloth the particles goes down the drain.[ec.europa.eu/research/environment/pdf/…
    – liftarn
    Aug 29, 2014 at 9:07
  • You mean that same drain, water and air that they don't want those "evil" "chemicals" going in :)
    – Matthew Whited
    Nov 18, 2014 at 16:35
  • I don't think the second claim holds up from the lit you cite. The Rutala et al source shows in table 1 that simply wringing out a microfiber cloth vs. not wringing it out has a 15% mean drop in effectiveness with a massive 25% standard deviation. That means its up to 40% less effective between wet and damp with detergent cleaner. The Norwex advertising is accurate but misleading. The cloths themselves stay clean without chemicals, but are not proven effective to clean surfaces without chemicals.
    – Josh Hibschman
    Apr 19, 2018 at 21:56

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