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Behind the Label: nanosilver

Pat Thomas

20th October, 2009

The powerful antibacterial nanosilver can now be found in everything from air fresheners and food packaging to babies' bottles and bandages. But has anyone looked at the risks?

The Ecologist has long been sceptical of the necessity and safety of antibacterial toiletries and household cleaners.

In spite of the fact that they are widely used in a variety of consumer products, many antibacterials work in ways similar to pesticides and, more alarmingly, antibiotics.

In a world where microbes (viruses, bacteria, fungi) are fast developing resistance to any kind antimicrobial substance, increasing resistance puts us at risk at home and in places where keeping microbial numbers at bay - such as hospitals - is crucial for health and safety reasons.

These facts haven't however stopped the anti-bacterial juggernaut from delivering newer and more powerful products - most recently nanosilver.

As you might expect the US is somewhat ahead of the UK in its use of nanosilver, but we are rapidly catching up. The market for antibacterial silver products is expected to grow to 110-230 tonnes of silver per year in the EU by 2010, and the US market is expected to be of similar size. The number of products incorporating nanotechnology is growing year on year. There has been a threefold increase from March 2006, when according to one US database there were 212, to August 2008, when there were 609. Of all types of nanotechnologies, nanosilver is the most commonly used in consumer products. To date there are over 200 such products on the global market.

Not just for vampires...

Silver has long been known as a potent antimicrobial agent. Early American pioneers, so we are told, used to put a silver dollar into urns of milk to keep it from souring. However, its use has exploded in recent years. Much of the silver used in products today is manufactured at the nano-scale, or smaller (see box) meaning it is present in extremely tiny particles that behave differently than larger particles and are especially potent.

The mining and process of silver is, like all precious metals, a filthy and polluting process, so silver begins with an environmental deficit before it even gets applied to other things.

What type of silver?
The smaller the silver particles are in any given product size the greater their relative surface area. Nanoparticles, for instance have a huge surface area; 15 to 1,500 square meters per gram. Ten grams might cover a football field if evenly distributed. The greater the surface area the more reactive and therefore powerful their effect. The problem is we simply don't know enough about how nanoparticles (or those particles even smaller than nanoscale) react in the real world for good or for harm.

Nano - Can be suspended in water or embedded into fabrics. To be called nanosilver the particles must be between 1-100 nanometres (nm) in diameter. A nanosilver particle may or may not possess an electrical charge to form silver ions.

Ionic - A single silver atom, becomes ionic when it gains or loses an electron (thus becoming negatively or positively charged). Ionic silver is much smaller than nanosilver, measuring 0.258 nm in diameter (a 9 nm nanoparticle contains around 24,000 silver ions) and can be dissolved in water. As the ions gain or lose their electrical charge they react with other substances.

Colloidal - a colloid is a mixture containing particles small enough to remain suspended in fluid for a long time. Colloidal particles can measure 1-1000 nm in diameter, which means that some colloids contain nanoparticles and some don't. A product can be colloidal and ionic and/or nano.

Elemental - the silver you find in nature, used in jewellery, coins, utensils and electronics.

Nevertheless, nanosilver is currently being put in and on a range of products including food packaging and containers, children's toys, babies' bottles, cosmetics, textiles, cleaning agents, air fresheners, chopping boards, refrigerators and dishwashers. It is also used in a variety of hospital settings, and you can also now buy nanosilver bandages and wound dressings.

Proposed regulation by the EPA in the US suggests that nanosilver is a pesticide and should be regulated as such. The nanotechnology industry has reacted fiercely to this, and argues that nanosilver should instead be treated like a cosmetic substance (and thereby subject to less stringent safety testing).

Unlike many new innovations, data on how nanosilver might behave in everyday use and in the environment have been fairly quick to emerge. Already there is evidence that nanosilver in clothing, or incorporated into washing machines, can leech into the environment with every wash. When it is finally deposited in watercourses or sewage treatment works, the antibacterial properties of nanosilver continue to operate, posing a threat to healthy (or artificial, in the case of sewage plants) ecosystems.

Enzyme choker


A recent Friends of the Earth report gives a good overview of what is known so far about nanosilver and its environmental effects. FoE has, in fact, been campaigning on this subject for years.

Silver's antibacterial properties come as a result of the way it acts as a catalyst, disabling the enzyme, or chemical lung, that bacteria need for their oxygen metabolism. Much like antibiotics, nanosilver doesn't distinguish between good and bad bacteria - it just kills any bacteria it comes into contact with, many of which are beneficial, even necessary, for our survival and the survival of other species.

Silver nanoparticles can kill the bacteria which, through a process known as denitrification (removing nitrates which build up through excessive fertiliser use), are used to clean waterways. Should they reach our soils, for instance via the water supply, nanosilver particles can threaten soil bacteria which play a key role in making nitrogen available to plants and the breakdown of organic matter.

At the same time as threatening beneficial bacteria in natural systems, nanosilver may compromise our own ability to control harmful bacteria. The potential for nanosilver to result in increased antibiotic resistance among harmful bacteria is a serious concern. Not only may certain harmful bacteria become resistant against nanosilver, but because of the type of resistance mechanism that might evolve, it is believed there is potential for these bacteria to develop a parallel resistance to around 50 per cent of currently used antibiotics.

While some alternative healthcare practitioners recommend taking colloidal or ionic silver orally, the human health effects of ingesting it - or even applying silver to your body over the long term - are unknown. There exists no published research evidence to back the mostly outrageous claims being made for such supplements.

All that glitters

It would be easy to point the finger of blame at the  corporate interests thrusting this new and potentially dangerous product down our throats - and into our socks. Certainly an analysis of the way nanotech is being 'sold' to the public tends to highlight a divide between those companies attempting to push the technology onto an indifferent market - for instance those who can produce a material but are still looking for a market to make the production process financially viable - and those where the technology could potentially serve a real need. Most applications of nanosilver seem to fall firmly into the former category.

But we also have to ask, yet again: why have we become so frightened of 'germs' that we feel the need to go to ever more extreme measures to vanquish them? Are there really people out there so terrified of their washing machine becoming a festering mass of life threatening germs that they feel the need to invest in a nanosilver coated machine? And if there are, wouldn't an investment in cognitive behavioral therapy be money better spent?

Nanosilver products, like all antibacterials, are frivolous and completely unnecessary for the vast majority of uses. The precautionary principle would demand that we stop buying these products and instead demand that manufacturers stop using nanosilver in their products, as FoE says, 'until nanotechnology-specific regulation is put in place to protect the public, workers and the environment, until all products containing nanosilver are labeled as such, and until the public is involved in decision making about the use of this particle.'

Pat Thomas is a former editor of the Ecologist

 

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