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

 
 
 
 

Marseille and Paris are crawling with rats. But it’s your problem too

A Parisian rat. Image: Getty.

You can very easily have a fine time in Marseille, but it is likely to be interrupted by rats.

The bloated and brazen beasts are so utterly convinced they own the place that they barely register any human presence to distract from their hedonistic excesses – throwing wild street parties, burrowing holes in overflowing bins, and darting in and out of exclusive harbourfront restaurants. We only really intrude when the occasional, blissfully oblivious rat is splattered across the cobblestones by a scooter.

For many residents, the whiskery foes have gone some way beyond a nuisance to represent a genuine menace. Rats have infested schools and taken over canteens. Pest control services claim they have broken into cars and gnawed through cables, which may have contributed to accidents. It is also alleged that they have caused Internet outages by attacking fibre-optic cables – continuing the venerable horror movie tradition of cutting the power seen in Aliens and Jurassic Park. Rats are also infamous and prolific traffickers of disease and have raised the threat of Leptospirosis.

Rat populations are fiendishly difficult to quantify, given their nocturnal lifestyle and that many live off-grid in the sewers; but by some estimates they now outnumber Marseille’s human inhabitants. Distress calls from the public to the city’s sanitation department and pest control services have increased, and the unofficial fifth emergency service has expanded its operations in response, laying poison traps and sweeping the gutters.

Several factors have contributed to the rat supremacy. Marseille’s Mediterranean climate has always been hospitable to rats, and a series of unusually warm summers – often passing 30°C – have made it more so. (Rats tend to stop breeding when it’s cold.)

City officials also bemoan the wanton waste disposal habits of their citizens, which have allowed large and easily accessible piles of appetising trash to accumulate. Marseille’s councillor for hygiene Monique Daubet recently complained the city has become a “five-star restaurant for rats”.

Others have suggested a series of strikes by garbage collectors gave the rat population a turbo charge it barely needed. A single pair of brown rats can spawn more than a thousand descendants within a year.

That formidable birth rate is one indicator of what the city is up against: the urban rat is almost a perfect predator. Millennia of human ingenuity has failed to remove them from our midst or negate the threats they pose. Rats are supreme survivors – scientists marvel at their survival on nuclear test sites – and they thrive in the most inhospitable environments. They can eat practically anything, but are neophobic, meaning they shy away from all but the most devious poison traps. The rodents are intelligent, resilient, and their ability to colonise new habitats rivals our own.

Faced with this adversary, the local authority has assigned more resources to the fight, through both the city’s sanitation department and the private extermination service A3DS. Both are reluctant to discuss their tactics and whether they are having an impact. But officials are also taking a tough line on public responsibility, insisting that residents dispose of trash after 7pm in sealed bags or face fines. The city has also proposed measures such as mobile dumps and new model bins that rats should find harder to access.

The Marseillais are also keeping a close eye on events in the capital: Paris’ rat problem may be even more severe, driven by flooding from the River Seine that has forced the rodents to seek higher ground. In recent years, rats have overrun the Louvre and forced the closure of public parks, as well as starring in viral video nasties that do little for the city’s image as the capital of romance.


Paris mayor Anne Hidalgo has sounded the alarm and invested millions of euros in a campaign against rats, which has seen thousands of raids in hundreds of parks and buildings, as well as the introduction of more secure bins, and fines levied against people accused of feeding the enemy. Her administration has also despatched an envoy to New York to study the city’s approach to its own notorious rodent community.

An international approach makes sense given that rats are on the march all around the world. Reported sightings have shot up in New York, Chicago, Boston, San Francisco, and Washington. One study estimated that rats inflict $19 billion of economic damage each year in the US alone. London has also seen an increase in reported sightings. Leading rodentologist Bobby Corrigan says the same patterns are playing out in the major cities of the Americas, Europe, Asia, and Australia.

And for much the same reasons. Contributing factors include “too few resources allocated an organised program for rat control,” says Corrigan. “Also, more people in our cities means more refuse, more overloading of the city’s sanitation budgets, less thorough removal of the kind of food shrapnel that escapes typical garbage collection. Each rat only needs about 30 grams of food per 24 hours to thrive and reproduce.” A warming climate also plays a part.

Poison traps and culls can only go so far, says the rodentologist, arguing that a holistic approach is required to head off the growing threat. “The best measure is a city organised in addressing the rats across all agencies,” says Corrigan. That means mobilising departments of sanitation, parks, housing, health, and sewers, as well as mayoral administrations themselves.

Society-wide civic participation is also essential. “Controlling rats takes everyone: every homeowner, shop owner, restaurant, grocery store, airport, and so on. Not to do so invites the risk of a “new and/or highly virulent virus” developing among our old enemies, he adds.

Research into sterilisation programmes offers some hope of a new weapon to repel and reduce the rodent hordes. But not enough for us to evade responsibility while rat populations grow and the threat increases. “If we don’t work together as the wise species we claim to be and present a scientific, multi-faceted organised effort against this very smart and organised smaller mammal, we can have no hope of defeating it,” says Corrigan. Time to man the barricades.