Why doesn’t the tube make handpoles out of self-sterilising metals? And what is grippage?

Why don't these kill germs? The interior of an ageing Circle line train in 2010. Image: Maurits90/Wikimedia Commons.

In February 2015, bacteriologists from Cornell University published their results after spending more than a year swabbing New York City’s Subway trains and stations for bacteria. The results sounded icky: not only are there hundreds of different microbial species living throughout NYC’s transit system, on the poles and seats and turnstiles that humans touch every day, but half of them were completely unfamiliar to science. Anthrax and the bubonic plague were among those bacteria which were recognised.

Of course, the fact that New Yorkers aren’t dying off like 14th century Europeans implies that the dirtiness (or, rather, perceived dirtiness) of the subway isn’t a pressing public health issue. The study authors were keen to point out that commuters shouldn’t overreact to the news.

The same will apply to London, both in terms of the microbes living throughout the Underground and in the near-non-existent risk they pose to travellers. Yet as I was sat on one of Transport for London’s new S Stock trains on the Hammersmith & City line last week, fully aware of the first signs of a cold in my nose and my throat, my thoughts drifted to that study.

TfL likes to colour-code its lines so that the interior decor of the trains matches the lines they run on (so orange on the Overground, blue on the Piccadilly, etc.). These new trains are running on the Metropolitan (purple), District (green), Hammersmith & City (pink) and Circle (yellow) lines – yet all are decked out in bright, garish yellow. God knows what’s living on those neon poles and handstraps that keep passengers from falling down.

We know that public transport is a vector for disease transmission, especially when it comes to seasonally-influenced illnesses like the flu. We also know that there are materials which self-sterilise – that is, they’re highly toxic for any single-cell organisms that are unfortunate enough to land on them. This “oligodynamic effect” was first discovered in 1893, and lots of different metals – from silver to aluminium, lead to copper – possess it.

So the question is: why aren’t the hand poles in Underground cars and on buses made of antimicrobial metal?

 

A Santiago metro station, complete with bacteria-killing handrails. Image: AntiMicrobialCopper.com.

In some parts of the world, the answer is actually “they are”. The subway system in the Chilean capital Santiago, for example, uses antimicrobial brass handrails, which were installed in 2011 as part of a wider healthcare campaign. But this is an exception, not a rule.

Jean-Yves Maillard is a pharmaceutical microbiologist from the Cardiff University who researches the use of antimicrobial materials in hospitals, and specifically the two most promising metals: silver and copper (or alloys of copper, rather). It turns out that these things kill germs best when “humidity is 100 per cent, so they are underwater – and that’s not how these surfaces exist on the metro, or Tube, or buses.”

Instead, to get a better idea of how well they work, he’s tested them when they’re dry (which means between 30 and 40 per cent humidity, which is typical for the UK), and when they have “droplets” (i.e. someone’s sneezed) on them.

The results are still impressive: within 30 minutes of contact with the most effective copper alloys, 99.99 per cent of Staphylococcus aureus bacteria – a bug responsible for everything from skin infections to respiratory diseases, and including the infamous antibiotic-resistant MRSA strain – were exterminated in the droplet test, while the dry test still saw around a 90 per cent reduction.

“When it's very dry – the worst case scenario, a very dry summer and so on, above 20 degrees – you'd get something like 99.99 per cent reductions within 30 minutes,” he said. “If someone sneezes, then after 30 minutes on that surface the bacteria is likely to be killed. I imagine for some viruses it would be the same as well. [But] if you haven't got droplets, then that activity really drops sharply. You'll get at most 90 per cent reductions, but probably less than 90 per cent, within 30 minutes. You'll kill some, but not all.” Silver was less effective in the droplet test, and not effective at all in the dry one.

This might make switching to copper-based antimicrobial subway and bus poles seem like an easy win that TfL missed when ordering its newest trains. But Maillard is keen to stress that there are some important downsides.


It rhymes with "fromage"

Firstly, if a surface is cleaned relatively frequently, then the extra cost from using more expensive materials might be more than those of simply paying for someone to wipe everything down a bit more frequently each day, for the same result. And these surfaces are no substitute for cleaning – Maillard emphasises that antimicrobial surfaces work “in addition” to cleaning, not as a replacement. And, when I contacted TfL, health & safety director Jill Collis made it clear that they clean the network “throughout the day and night” already.

The second reason is appearance. According to Collis, “the handrails in carriages are designed to be easy to see, meet safety standards and be suitable for daily use by millions of customers”. (I also discovered that the internal TfL term for the things that passengers hold onto isn’t “handrails”, but “grippage” – pronounced to rhyme with “fromage”.)

This is an important point – and TfL also said that, in accordance with the Vehicle Accessibility Regulations Act 2010, “any passenger handrail fitted in or to a rail vehicle must … contrast with the parts of the rail vehicle adjacent to that handrail”.

In other words, the bright colours on the Tube are primarily so that the visually-impaired are better able to see them. While the brass handrails of the Santiago subway may look somewhat classy, they also blend into the background in dark, underground spaces.

A third important issue is value for money. The handrails on the Tube are made of aluminium, which has a good ratio of weight to cost to strength; copper and silver, less so. “In hospitals, the debate is all about costs,” Maillard said. “[Surfaces] maybe get cleaned once a day, and with copper surfaces there are indications that at the end of the day the [the microbial burden] will be less than normal metal surfaces. That's the interest in it. But the big question is, is it cost effective?”

Then there’s even a fourth issue, most relevant to silver, which is that it perversely seems to make drug-resistant superbugs more likely. Making subway poles out of solid silver is, clearly, ridiculous, but it’s common for nano-particles of silver to be placed within other material to give it some antimicrobial properties – not as good as copper alloys, of course, but still something.

Maillard points to a January 2015 report from the EU Commission’s Scientific Committee on Emerging and Newly Identified Health Risks (Scenihr) into the possible dangers posed by the use of nano-silver in medical and consumer devices. It found that research is “urgently needed” into the possible toxic effects of long-term exposure to silver in consumer products, and also that the genetic adaptation of bacteria to silver could increase resistance.

“What you will find is that now you have a huge amount of surfaces that contain antimicrobials,” Maillard explained. “Lots of plastics, washing machines, photocopiers, in pens, televisions, television remote controls – most of them contain silver or nano-silver, because they don't affect the colour. The concentration that they use is very low, there are question marks over its efficacy, and questions about whether it's going to promote resistance of those organisms with those products.”

So, put it all together and it doesn’t look good for Tube poles that clean themselves. Copper alloys work best, but would have to be painted to comply with health & safety legislation, defeating the purpose. And, while it’s possible to stick silver particles into the paint as an alternative, it’s not very good, especially when the extra cost is factored in – and that’s without considering make it more likely that truly nasty bacteria can thrive and evolve on public transport.

Best stick to hand sanitising gel. Much easier.

Want more of this stuff? Follow CityMetric on Twitter or Facebook

 
 
 
 

There isn’t a war on the motorist. We should start one

These bloody people. Image: Getty.

When should you use the horn on a car? It’s not, and anyone who has been on a road in the UK in living memory will be surprised to hear this, when you are inconvenienced by traffic flow. Nor is it when you are annoyed that you have been very slightly inconvenienced by another driver refusing to break the law in a manner that is objectively dangerous, but which you perceive to be to your advantage.

According to the Highway Code:

“A horn should only be used when warning someone of any danger due to another vehicle or any other kind of danger.”

Let’s be frank: neither you nor I nor anyone we have ever met has ever heard a horn used in such a manner. Even those of us who live in or near places where horns perpetually ring out due to the entitled sociopathy of most drivers. Especially those of us who live in or near such places.

Several roads I frequently find myself pushing a pram up and down in north London are two way traffic, but allow parking on both sides. This being London that means that, in practice, they’re single track road which cars can enter from both ends.

And this being London that means, in practice, that on multiple occasions every day, men – it is literally always men – glower at each other from behind the steering wheels of needlessly big cars, banging their horns in fury that circumstances have, usually through the fault of neither of them, meant they are facing each other on a de facto single track road and now one of them is going to have to reverse for a metre or so.

This, of course, is an unacceptable surrender as far as the drivers’ ego is concerned, and a stalemate seemingly as protracted as the cold war and certainly nosier usually emerges. Occasionally someone will climb out of their beloved vehicle and shout and their opponent in person, which at least has the advantages of being quieter.

I mentioned all this to a friend recently, who suggested that maybe use of car horns should be formally restricted in certain circumstances.

Ha ha ha. Hah.

The Highway Code goes on to say -

“It is illegal to use a horn on a moving vehicle on a restricted road, a road that has street lights and a 30 mph limit, between the times of 11:30 p.m. and 07:00 a.m.”

Is there any UK legal provision more absolutely and comprehensively ignored by those to whom it applies? It might as well not be there. And you can bet that every single person who flouts it considers themselves law abiding. Rather than the perpetual criminal that they in point of fact are.


In the 25 years since I learned to drive I have used a car horn exactly no times, despite having lived in London for more than 20 of them. This is because I have never had occasion to use it appropriately. Neither has anyone else, of course, they’ve just used it inappropriately. Repeatedly.

So here’s my proposal for massively improving all UK  suburban and urban environments at a stroke: ban horns in all new cars and introduce massive, punitive, crippling, life-destroying fines for people caught using them on their old one.

There has never been a war on motorists, despite the persecution fantasies of the kind of middle aged man who thinks owning a book by Jeremy Clarkson is a substitute for a personality. There should be. Let’s start one. Now.

Phase 2 will be mandatory life sentences for people who don’t understand that a green traffic light doesn’t automatically mean you have right of way just because you’re in a car.

Do write in with your suggestions for Phase 3.