Written for E&T
How much do you need to worry about air pollution? E&T reporter Tereza Pultarova takes part in a King’s College London experiment to find out what Londoners inhale.
This week, I am a guinea pig in a King’s College London study trying to assess how much air pollution the city’s residents inhale. Each of the study’s eight volunteers uses a different mode of transport to get to and from their offices in the city. I am the cyclist in the group. Another person rides a motorbike. The rest use a combination of buses, Overground and Underground trains, and walking.
“The detectors are measuring black carbon – a type of particulate matter which generally comes from diesel exhaust. It’s mostly related to exposure to traffic, but we can also find it on the Underground as it can come from brake wear,” explains Andrew Grieve, King’s College air quality analyst, who leads the study. “The participants are also wearing a GPS watch, which will allow us to tie their exposure exactly to their location so we can build a picture of how exposure on routes differs.”
The study runs over two weeks. During the first week the volunteers use their regular routes. After that, Grieve will analyse our data and propose a different, quieter and less polluted route to see how much we could reduce our exposure by avoiding the worst air hotspots.
Air pollution has been making headlines lately. According to a King’s College study published in 2015, some 9,500 Londoners die every year due to health complications triggered by inhaling nitrogen oxides and toxic microscopic particles less than 2.5 micrometres in diameter (PM2.5). A recent study by the US-based Health Effects Institute concluded that in 2015 over 4.2 million people around the world died prematurely because of fine particulate matter alone.
In urban areas, diesel engine exhaust is the number one source of nitrogen oxides and particulate matter, and many UK cities struggle to keep both in check.
With every breath they take, residents of London, Glasgow and Leeds suck in a dangerous cocktail of toxic chemicals and invisible particles containing cadmium, mercury, nickel or ammonium. Combustion engines spew out some particles directly, while others arise in reactions of various precursor pollutants. Some particles are so tiny they escape the body’s natural protection mechanisms and penetrate deep into the lungs.
“There is no doubt that particles get taken up when they are inhaled,” explains Professor Jonathan Grigg from Queen Mary University of London, a leading expert on effects of air pollution on human health. “They are taken up by B cells like macrophages and that would stimulate cells to produce inflammation cytokines and inflammatory mediators. That’s one explanation for the effect in the lung and also at distant sites of the body, because the mediators can get across into the bloodstream.”
Air pollution worsens allergies. Those with heart disease, asthma or lung cancer are more likely to experience complications or die during high air-pollution spells. Evidence is mounting that polluted air can contribute to a wide range of health problems with no direct link to breathing such as diabetes or neurological disease. A recent study by the University of Birmingham found every extra 10 micrograms of PM2.5 per cubic metre of air increases the risk of dying of any type of cancer in elderly people by 22 per cent. Pregnant women breathing highly polluted air are more likely to go into labour prematurely.
In addition to the monitored PM10s and PM2.5s, there is a large amount of the so-called ultra-fine particles, which air-quality networks do not regularly measure. Less than 100 nanometres in diameter (you could fit more than 25 across the width of a human hair), the ultra-fine particles make up a relatively low proportion of total particulate matter mass. If counted by particle, however, these are the most abundant.
The macrophages rid the body of some particles, but some stay in the lungs for the long haul.
“If you look at the lungs of people who are non-smokers, you can see accumulation of carbon in the tissues,” says Grigg, who recently founded Doctors Against Diesel, a campaign representing medical professionals calling for the abolition of diesel-powered vehicles in the UK’s cities.
Yet the lungs are probably not the only dumpsite for air pollution particles. Worryingly, multiple studies have indicated that ultra-fine particles might be able to cross from the alveoli to the bloodstream.
In September last year, a study published in the journal PNAS by Lancaster University Professor Barbara Maher and her team stirred up the scientific community. Maher set out to find whether magnetic air pollution particles could penetrate into the most important human organ – the brain.
“Wherever you have particles formed by combustion processes, heating or by friction from braking, you always produce some strongly magnetic particulates,” Maher explains.
“We can make magnetic measurements of airborne pollution and we can identify where air pollution is highest because of magnetic particles. Wherever you have more particulate pollution, you also have more magnetic particulate pollution.”
The connection between magnetic air pollution and the human brain intrigued Maher for one particular reason – she knew that deposits of magnetite could be found in brains of Alzheimer’s disease sufferers.
The widely accepted hypothesis that this magnetite is produced in the brain as a result of the organ’s chemistry going awry didn’t fully satisfy her.
“Knowing that there was so much magnetite available in the atmosphere in urban locations, my question was – could it be that some magnetite in human brains is not forming inside the brain, but is coming from external pollution sources?” says Maher.
“Many of these pollution particles are less than 150 nanometres in size so I thought it would be difficult for the body not to actually take up some of them.”
The Lancaster University professor ordered a set of brains from the Manchester Brain Bank and another bunch from Mexico City, which has struggled with extreme air pollution for years.
In the brains, Maher and her team found two types of magnetite particles – geometric crystalline particles corresponding with the metabolic hypothesis, but also a large amount of smooth spherical magnetite.
“The rounded particles varied mostly between 10nm and 150nm and they were frequently associated with other types of similar looking particles of other metals, particularly nickel, platinum and copper,” Maher says. “When we compared those particles with airborne magnetite pollution particles, they looked exactly the same.”
For every natural crystalline particle, the researchers found about a hundred spherical ones. The most magnetic brain belonged to a 32-year-old car crash victim from Mexico City.
So how much air pollution does a Londoner inhale?
I am anxiously awaiting the results of the first week of the experiment. I know that some areas I pass through on my 45-minute cycle to work are shining red on the London air pollution map, especially during rush hour, and I am getting seriously concerned about the colour of my lungs and magnetic properties of my brain.
“From what I see, your commute constitutes almost all of your exposure on a normal day,” Grieve scrolls through pages of graphs. “In your home and in your office, there are barely any black carbon particles, the concentration is very low – less than two micrograms per cubic metre of air. I can clearly see your morning and evening cycle,” he points to two ragged spikes towering like volcanoes above the flat landscape of my indoor exposure. The oscillating line hits up to 35 at one point, then drops to 25 and 16 micrograms.
“Yet the worst peak is actually here,” the long-haired scientist pauses at a protrusion from my Saturday afternoon. “Do you remember what did you do at that time?”
“I think I took an Underground train to central London to meet a friend,” I am trying to remember.
The reading says 70 micrograms per cubic metre – twice the highest peak from my daily bicycle rides. I am relieved that my decision to cycle in London seems sound. However, Grieve believes I could cut down my exposure even further if I fine-tune my route to avoid areas with the highest concentrations.
Travelling smart might be the wisest and least aggravating choice Londoners can make to protect themselves against the omnipresent carcinogenic cloud (WHO lists diesel exhaust as a class one carcinogen, suggesting the health scare is well founded on facts).
Mayor of London Sadiq Khan responded to growing concern by introducing a £10 toxicity charge for diesel vehicles manufactured before 2006. Starting from October 2017, up to 10,000 drivers a day will have to either pay to enter central London or leave their pre-Euro 4 cars at home, the Mayor says.
However, some experts admit the measure may only have a cosmetic effect.
“Euro 4 vehicles don’t necessarily have a particle trap,” says Chris Brace, professor of automotive propulsion at the University of Bath. “There were some early adopters of particulate filters in 2006, but if you wanted to be safe and wanted to have all the vehicles with particulate filters, you would have to have Euro 5.”
Not only do diesel engines spew out soot, they also produce considerable amounts of nitrogen oxides, unlike petrol-powered cars, which have a worse carbon footprint. The disconcerted public is therefore increasingly calling for diesel to be shunned altogether. Such calls, however, do not resonate in the engineering community.
“What would help enormously is to introduce new technology more quickly, to encourage people to buy more modern vehicles,” says Brace. “Starting with Euro 5 vehicles, particulate pollution is no longer a problem. The filter removes pretty much everything. The amount of particles coming out at the tail pipe is as low as in gasoline engines.”
Professor Brace is optimistic, even when it comes to the persistent nitrogen oxide issue that infamously prompted Volkswagen to start installing defeat devices into its passenger diesel cars to cheat in laboratory emission tests.
“There are already passenger diesel vehicles in the market that are performing as well on the road as in the laboratory in terms of oxides of nitrogen,” says Brace. “I think what you are seeing at the moment are variations at the rates of progress by each of the manufacturers.”
Ray Minjares, who leads the Clean Air Program at the International Council on Clean Transportation, agrees. “Emission control technology does exist to make diesel cars as clean as petrol-powered ones and the ICCT is seeing this technology placed on Euro 5 trucks and buses,” he says.
“The problem we see is the failure to apply this technology on diesel passenger cars, which has resulted in high real-world diesel NOx emissions. Since Europe is still in the process towards adopting a strong real-world driving emissions scheme, and since vehicles sold today are not yet required to meet it, the challenges in bringing down real-world diesel NOx from passenger cars is real and will remain so in the next few years.”
What do you do then? Are you supposed to wait quietly for the current diesel fleet to regenerate, knowing that pre-historic vehicles are still on the roads exceeding current emission standards, tens or even hundreds of times?
Grieve hopes his data will empower health-conscious Londoners (as well as residents of other busy cities) to take action to protect themselves against increasing blackening of their lungs.
“Our experiments show that when you walk, you generally have a lower exposure than when you are on a bus. Overground trains tend to be less polluted than Underground trains,” he suggests.
“You can also considerably reduce your exposure by taking a walking or cycling route one block away from main roads. You would have perhaps 40 per cent less pollution there and if you choose this route every day, over a few years the difference to your health would be considerable.”
My Week Two data shows a consistent 30 per cent decrease in the amount of black carbon PM2.5 particles measured. The 10 minutes of extra pedalling clearly paid off.
Read about six innovative ideas for cleaning up the pollution from the air in cities.