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- Herausgeber: Icon Books
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
An accessible and hard-hitting look at the facts behind air pollution in everyday life. Take a deep breath. You'll do it 20,000 times a day. You assume all this air is clean; it's the very breath of life. But in Delhi, the toxic smog is as bad for you as smoking 50 cigarettes a day. Even a few days in Paris, London or Rome is equivalent to two or three cigarettes. Air pollution is implicated in six of the top ten causes of death worldwide, including lung cancer, heart disease, stroke, and dementia. Breathless gives us clear facts about air pollution in our everyday lives, showing how it affects our bodies, how much of it occurs in unexpected places (indoors, inside your car), and how you can minimise the risks. Rooted in the latest science, including real-time air-quality experiments in city streets and ordinary homes, it will allow you to make up your own mind about the risks and trade-offs of modern living - wherever in the world you are.
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Contents
Introduction
You’ve probably seen those side-by-side photos on cigarette packets. On the left, the healthy pink lung of a non-smoker; on the right, the clapped-out, blackened lump from a hopeless tobacco addict. What you might not realise is that air pollution – the kind you might be breathing right now – can have horribly similar effects. In Delhi, one of the world’s dirtiest places, chest surgeons estimate that the tiny, toxic specks in the smog (technically, they’re known as ‘PM2.5 particulates’) are as bad for you as smoking 50 a day (just like smoking, they can lead to pneumonia, asthma and lung cancer). Even a few days in Paris, Milan, London or Rome is like puffing your way through two or three cigarettes (either way, you’ll be exposed to a similar amount of PM2.5s).[1]
According to one recent study, there are fifteen cities in the world where the air is so toxic that active exercise will do you more harm than good. But you don’t have to live in a filthy metropolis to feel the harsh effects of polluted air. Even if you live in a tiny town, you still might wince in damp December when that strange, metallic tang hits your tongue, as the fug seeping from stalled exhausts bubbles up from the cauldron of the streets into a low-level cloud of malignant mist. Maybe you’ve worried about cycling in the sooty slipstream of an old bus, or drummed your fingers in a jam for half an hour, sucking hard on the tailpipe of 2the car in front? Ever regretted breathing in just a bit too deeply as another filthy truck wheezed by? Have you coughed or sneezed into your handkerchief and made the mistake of peeping, with hair-rising horror, at the nasty, black, Jackson Pollock of a mass you’ve just hurled up?[2]
Maybe it feels like a commendable public service you’re doing, cleaning the air one breath at a time? After all, the filth you inhale from those dirty diesels lodges in your lungs, so the air you exhale is far nicer. You might be a kind of human Hoover, but don’t be fooled into thinking you’re making the world any cleaner. Even if all the people in a megacity like Mumbai sponged up all the pollution they breathed in, they’d still be cleaning as little as 0.01 per cent of the air swirling around them.
And the other catch, of course, is that your lungs clean the air at your own expense. If you’re reading these words somewhere in an average world-class city, air pollution is shortening your life by anything from a few months to a few years. Collectively, the air we prize – the breath of life that keeps us alive – is positively toxic. It’s killing more people prematurely than almost anything else on the planet: the equivalent of 7–10 million each year, which is five times more than road accidents, three times more than tobacco smoke, fifteen times more than all wars and violence and more than malaria and Aids combined. That’s 2,500 times as many people as died in the 9/11 terrorist attacks, every single year. The SARS-CoV-2 (COVID-19) coronavirus that swept the world in 2020 was initially predicted to kill about 20 million – but in the noise and the panic, we forget that air pollution kills five times that many every decade. Polluted air is now heavily implicated in six of the world’s top ten causes of death; not just obvious lung and breathing problems, but heart disease, cancers, stroke and dementia. These bald statistics mask a vast human cost. Any of 3the world’s millions of air pollution deaths could follow years of chronic suffering: if dirty air is going to kill you, medical research suggests it will make your life smoulder for a decade before it snuffs the wick out for good.[3]
You can see the effects of air pollution wherever you look, however you measure. In Delhi, test-match cricketers gratefully gasp from oxygen cylinders while they wait in the safety of the pavilion. In parts of China, filthy air will kill you five years too soon. In Hong Kong, the smog is sometimes so grim that tourists stand in front of giant, sunny photographs of the city to take their selfies instead. In Mongolia, winter air pollution is strongly linked to high rates of miscarriage. In Europe, national governments are allowed a certain number of excessive pollution episodes each year; in London, the British burn through their entire annual quota during the first week of January. According to the World Health Organization, 92 per cent of the world’s people live in places where its air quality guidelines aren’t met. You’re probably among them.[4]
Sometimes the effects of pollution are easy to spot: think soot-blackened city streets or praying cathedral angels blurred to gargoyles by acid in the air. From the Colosseum to the Taj Mahal, powerfully toxic air is cracking and staining the world’s oldest buildings, turning priceless heritage – our collective civilised memory – to dust. Just as often, it’s a case of out-of-sight, out-of-mind: although the pollution we make here and now might not bother us immediately, it can cause problems half a world away and half a century in the future. In the last few years, for example, agricultural researchers have found that ground-level ozone pollution from North America is responsible for the loss of 1.2 million tonnes of wheat each year in Europe. Others have found intriguing links between decades-old lead pollution (from paint 4and poisonous vehicle fuel) and patterns of crime and antisocial behaviour in no fewer than seven separate countries.[5]
Figure 1. Air pollution is one of the world’s biggest killers. When we fully understand the health problems it contributes to, it may even turn out to be the biggest killer of them all. Figures in brackets show millions of deaths per year. Source: World Health Organization.1
Compelling1 though these arguments sound, not everyone is persuaded by them. Isn’t nature one of our biggest polluters? What about hay fever? Doesn’t it affect more children (roughly 40 per cent) than traffic? What about Icelandic volcanoes that spew out 5sudden smoke, like the one in 2010 that grounded 100,000 European flights with little or no warning? How about bushfires? Farm pollution? Dust from the desert? Now this is all true, but if you crunch the numbers, you’ll still find the number of deaths from human-caused pollution exceeds natural-pollution deaths by a factor of ten.[6]
Perhaps you think pollution is nothing new and therefore nothing to worry about – an irritating throwback to the Industrial Revolution? You’d be half right, at least. Air pollution is as old as human history, dating back around a million years to the first use of fire; but 300 years after the invention of the steam engine – arguably the dirtiest machine ever developed – it remains the biggest environmental threat to public health. Though parts of the world are indisputably cleaner today than they were during Victorian times, the problem of pollution has never really gone away. The unavoidable reality of us being so many, on such a small planet, is that we’re constantly recycling the same air – and inventing ever more ways to make it dirty.
The history of air pollution includes plenty of denial that it was ever really a problem. Back in the 1880s, Chicago coal magnate Colonel W.P. Rend proudly boasted: ‘Smoke is the incense burning on the altars of industry. It is beautiful to me … You can’t stop it.’ A century later, US President Ronald Reagan mounted a robust defence of the right to pollute in the name of economic progress: ‘Approximately 80 per cent of our air pollution stems from hydrocarbons released by vegetation, so let’s not go overboard in setting and enforcing tough emission standards from man-made sources.’ At best, that’s a non-sequitur: Reagan was right that trees pollute, but wrong to conclude it grants us a licence to pollute as well. Trees can’t help themselves; we can. If money is your measure and you think pollution a price worth paying for progress, which 6is what Reagan was really arguing, you need to consider the World Bank’s finding that dirty air costs the planet $5 trillion a year, including $225 billion in lost work days alone. That’s about a third of the total cost of the financial crash of 2008 each year. In the UK, pollution costs £6–50 billion annually; in the US, estimates range from $45–120 billion. Globally, pollution chops 6 per cent off GDP – to put that in context, the world spends 2.2 per cent of GDP on defence and 4.8 per cent on education.[7]
Reagan died from dementia – a progressive condition increasingly correlated with pollution (one substantial recent study of 250,000 Canadians aged 55–85 found a clear association between the incidence of dementia and levels of air pollution). If Reagan had known that, would he have still defended the toxic clouds coughed out by cars and power plants? Supposing, just supposing, his dementia had anything to do with pollution, had it dulled his brain to an argument that might have helped save him? Are we all in the same leaky boat now? Our blunted brains slowing to mush, fingers drumming the traffic-jam dashboard, bothered neither by the past nor the future, the car in front nor the car behind, simultaneously lost and going nowhere in a breathless present that never ends? How frightening, if air pollution is making us stupid to the very problems it’s causing.[8]
If all this sounds bleak, it needn’t be; there are lots of solutions. Though technology caused the problems we experience today, it also offers plenty of fixes. We have lead-free fuel and catalytic converters; HEPA-filtering vacuum cleaners for asthma sufferers that trap more dust than ever before; ‘rocket’ and solar cookers that free people in developing countries from squandering their lives collecting wood fuel and choking to death (literally) over its fumes; bridges with absorbent concrete that soak up traffic fumes or construction dust; there are even buses with built-in 7air filters on their roofs that suck smog straight from the sky. We’ve got the laws, too – from general worldwide curbs on passive smoking that will save millions of lives to specific national fixes like the US Clean Air Act, which has paid for itself in health and other benefits 30 times over.[9]
Figure 2. Air pollution costs the world $5 trillion ($5,000,000,000,000) a year – more than the GDP of most countries and equivalent to spending $5 million a day since Roman times.
People power is also making a difference. A few years ago, 800,000 inspiring Indians from Uttar Pradesh (where dirty air cuts 8.6 years off people’s lives) did their bit for climate change and pollution when they collectively planted 50 million tree seedlings in a mere 24 hours – and earned a worthy Guinness World Record in the process. When the British branch of the environmental group Friends of the Earth offered its members a chance to measure the pollution in their local streets, some 4,000 individuals and groups jumped at the chance. In the United States, over a million parents are members of an energetic pollution-busting group called Moms Clean Air Force, while 100,000 people take part 8in California’s Clean Air Day each year. In China, an investigative film about the country’s toxic air pollution was viewed 200 million times (before being banned by the government). Even in cyberspace, where you might think real-world problems are blissfully academic, over 3 million Facebook users have ‘Liked’ air pollution (listed it as an interest).[10]
Numbers like this confirm that air pollution is a matter of huge public concern. So why is it still a problem? One reason is that air pollution is complex and multi-faceted: it’s a thorny thicket of an issue that mixes physics with medicine, chemistry with epidemiology and public health, geography with many different flavours of international law, and politics with economics. As we’ve already seen, the causes and effects can be separated by continents and decades (asbestos exposure, for example, can take as long as 50 years to translate into cancer), which makes the issue far harder for people to care about. As usual, there’s the false and lazy trade-off between environmental issues and economic priorities: the idea that environmentalism is middle-class, naive dilettantism, rather than a sincere concern for the 3 billion of the world’s poorest who have to burn solid fuel to stay alive and the 4 million of them who die from indoor smoke pollution each year. Another reason – and it sounds fatuous, but it’s perfectly true – is that there’s far more air wrapped around the world than you might think; and once it’s dirty, it tends to stay that way.[11]
Ultimately, there’s a lot to understand about air pollution, the sheer scale of which can leave you feeling powerless. That’s where this book – a whistle-stop attempt to make sense of our polluted world – comes in. Starting with an overview of air pollution and its history, we’ll explore the causes, effects and solutions in easy-to-understand, accessible terms. You won’t need to be a 9scientist, a doctor, an economist or a politician to get something out of these pages – just a concerned citizen with a keen interest in clean air. Perhaps a parent who walks their children to school or a cab driver who sits in traffic, worrying about what’s blowing in through the air intake.
So sit back, relax and read on.
It’s time to get your breath back.
1 Comparing how different public health problems like air pollution harm large populations is PhD-level complex and not something I’m going to go into in detail. I use the term ‘early deaths’ throughout this book for simplicity, but it’s only part of the picture: not everyone harmed by pollution will die. There are numerous ways of quantifying the overall health impact, from a simple tally of deaths or years of life lost (so the death of a child counts for more) to disability-adjusted life years (which count suffering before death) and age-standardised death rates (which allow for some countries having older populations than others). For more detail, see the State of Global Air project’s website and annual reports (www.stateofglobalair.org).
CHAPTER 1
What’s your poison?
A closer look at the air you’re breathing
The world’s most poisonous substance, botulinum toxin, is so deadly that a mere ten-millionth of a gram would be enough to kill you. Is it hyperbole, then, to call air pollution a poison? It certainly sounds mischievous, even misleading, to talk about dirty air the way we’d refer to cloudy brown bottles, branded with a red skull and crossbones, locked in the back room of a Dickensian apothecary’s store. But it isn’t misleading at all. Poison is a substance that kills or harms you when enough of it enters your body; air pollution has the same effect, albeit more slowly, more cruelly and less obviously. Poisoned by pollution, your death won’t take seconds or minutes, but years or even decades; chances are, you won’t even notice you’re being poisoned. But millions of people will die early this way, this year and every year for the foreseeable future thanks to the long-term effects of breathing poisoned, polluted air.[1]
Seven to ten million early deaths might not sound many in a world of nearly eight billion. It’s about one person in a thousand, which sounds even less impressive. But poison doesn’t simply kill. For every person who eventually dies from the chronic effects of dirty air, many more suffer pained and stunted lives. Living or dead, many are victims of seemingly unconnected medical problems like heart disease, stroke, dementia, diabetes and mental 12illnesses that are, in fact, increasingly correlated with pollution. According to the World Health Organization, air pollution causes a quarter of all deaths from heart disease, a quarter of those from stroke, over 40 per cent of those from chronic obstructive pulmonary disease (COPD1) and almost a third of those from lung cancer. Some 90 per cent of us – 6.9 billion people – breathe polluted air, indoors or out, and will have anything from a few months to a few years shaved off our lives as a result. If you’re 23 at the moment, whether you’re going to live to the age of 85 or 87 might seem remote and academic; if you’ve reached 75 already, and the damage of living in a choking city is already done, it might give you more pause for thought. Back in 1752 in Britain, so the famous story goes, people rioted over the eleven notional days of life they thought they were going to lose when the calendar switched from Julian to Gregorian. A quarter of a millennium later, no one’s protesting that much about the months and years of life that pollution really does steal away.[2]
Even knowing all of this, it can be hard to accept dirty air as a poison. The case against air pollution feels tenuous and circumstantial: it’s almost impossible to point to certain victims – or, as scientists enjoy noting, no one’s death certificate quotes ‘air pollution’ as the cause. Perhaps that’s because ‘air pollution’ itself feels like an oxymoron; instinctively, we harbour the notion that, in a more ideal world, we might all be breathing naturally clean air. As we’ll see in later chapters, that idea is wrong-headed in three quite different ways. First, even ‘natural’ air can fall foul of a simple definition of pollution. From billowing volcanic plumes to aromatic pine trees and wild (bush) fires sparked by lightning 13strikes, there are plenty of examples of natural air pollution that have nothing to do with humans. Second, it’s hard to conceive of a world with completely unpolluted air and there’s little prospect of achieving it any time soon. Virtually every step forward in human civilisation to date, from the use of fire to (as we’ll see later) the silent sweep of electric cars, has involved making copious amounts of pollution. Humans are essentially – not accidentally – polluters, and perhaps they always will be. Third, we often pollute in well-meaning ways: whether you like it or not, you’ll make air pollution building a school, driving an ambulance, putting out a fire or baking birthday cakes for your daughter. It’s hard to see innocuous things like this as ‘poisoning people’.
According to one authoritative definition, ‘poisons can be swallowed, absorbed through the skin, injected, inhaled or splashed into the eyes’; just like a poison, air pollution can be absorbed through the skin and harm your eyes, as well as being breathed in.2 In other respects, pollution has a different modus operandi from poison. Poisons startle us because they’re so dramatic and rare; air pollution, by contrast, seems humdrum and ubiquitous. While it’s tempting to focus on its worst victims (those multi-million deaths a year), it’s important to remember that they’re just the tip of the iceberg. Out of sight are $225 billion worth of lost work days, endless gasps from the asthma inhaler, countless trips to hospital or visits to the doctor and many more subtle problems that medics refer to as ‘subclinical effects’ (irritating health niggles not worth bothering the doctor about). But while the effects of air pollution are spread through all humanity, they affect some much more than others. Poor people, ethnic minorities, the elderly, children 14in schools near busy roads, people living in developing countries, those with chronic medical conditions, even the unborn – all these are among the hardest hit. (We’ll explore the medical aspects of air pollution in detail in Chapter 8.)[4]
Why does air even matter?
If you live a busy modern urban life, stressed by the school run or the hurtling charge of the commute, you might have explored things like meditation and mindfulness as a calming form of escape. One of the fascinatingly counter-intuitive things about meditation is the way it forces you to focus on something you normally ignore: your breathing. In one common technique, you visualise the air flowing in and out of your nose until your mind slips its chains and you float away on a magic carpet of altered consciousness. Air, in that moment of transition, in the short-haul flight from stress to calm, is all that matters. But why, in the bigger scheme of things, does air matter? Why is there even air on our planet at all?
Everything on Earth is pulled in by its gravity – even the blanket of gas we call the atmosphere – and it’s hard for us to visualise and understand the implications of this. Earth’s entire atmosphere is about 600 kilometres or 370 miles thick (about 1,500 times taller than the Empire State Building). But the bit that really interests us – the troposphere – is the 18 kilometres (11 miles) or so closest to the ground (50 times the height of that skyscraper). This is the home of weather, what we generally regard as ‘air’, and therefore air pollution. If you swim, snorkel or scuba dive, even if you merely duck down in your local pool, you’ll be well aware of water pressure: the deeper you go, the more water there is above you and the harder it pushes down on you. Exactly the same logic applies to 15the gas that surrounds Earth. But, although we’re tacitly familiar with the abstract idea of air pressure from weather forecasts, the practical reality of living in a compressed molecular soup, under 600 kilometres of air – like fish in the ocean, but forced to clump around on the seabed – somehow eludes us.
Air is something we can neither see nor feel (unless it whips past us quickly), but the gases it contains drive almost all life, all the same. Plants powered by sunlight photosynthesise, mopping up carbon dioxide and ‘breathing’ out oxygen; animals, nibbling on those plants and on one another, do (broadly) the reverse in a process biologists call respiration. If you’re any kind of scientist, or merely curious, this prompts some fascinating questions. If, as we learn at school, air is about 80 per cent nitrogen and 20 per cent oxygen, why is it the oxygen our bodies use and not the nitrogen? Are there credible creatures that exist, anywhere on Earth, that don’t breathe oxygen? And if pollution is such a problem, and has existed for at least a million years, why haven’t our bodies evolved to dodge around it?
The answers are fascinating, too. Oxygen is the most useful chemical in the atmosphere – more generally reactive than nitrogen and better for liberating energy – and evolution has tapped into this. Our bodies can easily make energy from food with chemical reactions involving oxygen, whereas using nitrogen (or another gas, like hydrogen) is trickier and sometimes even energy-intensive. (Think of plants, which depend on lightning strikes to convert tightly bonded nitrogen in the air into a ‘food’ they can take up from the soil.) Even so, a few creatures do rely on oxygen less than we do, including snakelike giant tube worms, some 2.4 metres (almost 8 feet) long, that thrive in the bubbling jacuzzi of hydrothermal vents in the ocean floor, breathing hydrogen sulphide (the chemical smell we know as rotten eggs). And 16there are microscopic blobs called loriciferans that live at the bottom of the Mediterranean Sea, which can survive without any oxygen at all. It’s no coincidence that creatures like this dwell on the seabed; landlubbers, given the choice, will pick oxygen every time. As to why we haven’t adapted to survive pollution, we simply haven’t had time. Human evolutionary changes take millions of years, while the real problem caused by fire – dangerously concentrated urban pollution – dates back only a couple of thousand years. As we’ll see during this book, pollution itself is also constantly evolving: the often-invisible, 21st-century kind is very different from the in-your-face filth that people breathed in centuries gone by.[5]
Perfect air in a perfect world
If we could subtract humans from the picture altogether, what would theoretically perfect, unpolluted air actually look like?
Just as we learn at school, dry air is almost entirely made of two gases, nitrogen (78 per cent) and oxygen (21 per cent). Most of the rest is argon (one of those mysterious ‘noble’ gases that doesn’t do much at all) and there’s a dash of carbon dioxide. There are also tiny (trace) amounts of gases such as helium in Earth’s atmosphere (60 times less than carbon dioxide) and flammable hydrogen (10 times less again).
Suppose you took a volume of air the size of a modest bedroom (about 25 cubic metres or 33 cubic yards). Nitrogen would fill all but a layer 50 centimetres (20 inches) or so thick, which would be the oxygen. Argon would line roughly the bottom 2.5 centimetres (1 inch), and the carbon dioxide would fit in five milk bottles in the corner. Now this is a slightly misleading picture, since 70 per cent of our planet is covered by water and the air isn’t, in fact, 17dry at all. But even adding in water vapour doesn’t change things that much. The other gases politely shift up to make room: adding about 3 per cent water vapour to the air (a typical amount) dials down the nitrogen content (to about 75 per cent), the oxygen content somewhat less (to 20 per cent) and the other gases less still.[6]
One way to appreciate the idea of a ‘perfect’ Earth atmosphere is to contemplate the atmospheres of other planets. All the speculation about aliens nipping down to Earth in flying saucers overlooks a fundamental problem with interplanetary tourism: curious creatures from outer space would struggle to survive in a climate as radically different as the one they’d find on Earth. On Mars, for example, the atmospheric tables are completely turned: the ‘air’ is almost entirely (95 per cent) carbon dioxide, while the gases common on Earth (nitrogen, oxygen and argon) are present there in only tiny amounts. Water, which may once have been abundant, is now very hard to find. Jupiter, on the other hand, is dominated by swirling clouds of hydrogen (about 90 per cent) and helium (almost 10 per cent), with trace amounts of things like ammonia, methane and water vapour.[7]
Imperfect air in an imperfect world
Back on our own imperfect Earth, depending on where you are, what you’re doing and what’s around you, the breath you’re sucking in right now will contain many different air pollution gases and dirt particles. At the dawn of the 21st century, pollution scientists at the World Health Organization were tracking roughly three dozen significant chemicals known to present a risk to people and planet; of these, half a dozen or so are of most concern:[8]18
Sulphur dioxide
Despite the growing importance of powering our planet with clean, green solar panels and wind, around 85 per cent of the energy the world uses (and two thirds of our electricity) still comes from fossil fuels; mainly coal, natural gas and oil. Coal might look like pure black chunks of carbon, but it also contains a few per cent of sulphur. When coal burns, the sulphur blends with oxygen in the air to make sulphur dioxide (SO2), a pollutant that causes breathing problems and contributes to heart disease. SO2 is the stinking gas belched out by the steam engines and coal-fired electricity plants that powered our industrialisation – the whiff of nostalgia you can smell if you ride the steam train on a heritage railway (as I will do, in the name of science, later in this book). When it meets water in the air, SO2 turns to sulphuric acid and falls back to Earth as acid rain.
Interestingly, the very same sulphur dioxide is involved in a more minor but no less irritating example of air pollution: the way onion slicing brings tears to your eyes. When sulphur dioxide from factories and power plants returns to Earth as acid rain, it adds sulphur to the soil. Onions absorb that sulphur and use it to make a complex, tear-gas-like chemical (known as syn-Propanethial-S-oxide), which is released when you chop them up in your kitchen – and makes you cry.[9]
Ozone
The kind of oxygen our noses haul in contains two married molecules, O2, but a mutant form of the same stuff has an extra one, O3; a kind of chemical ménage à trois, it’s the rapacious, predatory gas known as ozone. Ozone gets a mixed press. Historically, people confused it with the fresh, bracing air you couldn’t get enough of when you stood by the sea shore. High in the atmosphere, in the 19infamous ozone layer, it’s an effective sunblock protecting us from skin cancer brought on by the sun’s UV rays; at ground-level, it’s an aggressive and poisonous pollutant that plays a key part in smog, worsens breathing problems and destroys crops and trees. Ozone is not normally a problem indoors; O3 quickly transforms itself into harmless O2 when it bashes into something like a window or a wall.
Ozone is toxic and in very high concentrations (over 50 parts per million) can cause death within minutes. Despite this, alternative medicine practitioners have long touted something called ‘ozone therapy’, which involves pumping the stuff into a patient’s body, supposedly to cure a wide variety of medical conditions, from Aids and arthritis to heart disease and cancer. The US government’s Food and Drug Administration notes that there is ‘no known useful medical application’ of ozone and effectively banned all such uses in 2016.[10]
Nitrogen oxides
Flames look wantonly destructive, but the burning that powers them is a methodical chemical reaction (chemists call it combustion) in which carbon-based fuels react with oxygen in the air to give off (ideally) carbon dioxide, water and a rushing blush of heat. The trouble is, both fuel and air contain some nitrogen. That means that combustion – in things like wildfires, power plants and car engines – also produces nitrogen oxides (nitrogen oxide and nitrogen dioxide, often written NOx for short) as a by-product. As we’ve already seen, nitrogen gas is normally unreactive, but in the dizzy heat of a roaring flame, some of the oxygen that ought to be burning up fuel reacts with nitrogen to make NOx pollution instead.
Nitrogen oxide, nitrogen dioxide (which exacerbates health problems such as breathing difficulties) and ozone react together 20in various ways, under various conditions, to produce such things as acid rain and smog. But smog’s not always the greatest danger. As we’ll see later, using a gas stove can produce nitrogen dioxide levels in your kitchen that are many times greater than you’ll breathe in a smoggy city street.[11]
Carbon monoxide
Thanks to better public health education, more of us know about the risk of carbon monoxide (CO) poisoning, which happens when fuels burn with too little oxygen to make generally harmless carbon dioxide (CO2). While people in developed countries are used to having handy, electronic CO alarms next to their gas fires and boilers, those in developing nations are still at great risk from indoor CO pollution. Outdoors, there’s not much most of us can do about carbon monoxide snaking from car tailpipes, steelmaking furnaces, petroleum refineries, garden bonfires or forest fires. Bizarrely, back in the 1790s, carbon monoxide was tested as a treatment for various ailments by one Thomas Beddoes of the curiously named Pneumatic Institution for Inhalation Gas Therapy in the British city of Bristol: he believed it gave people rosy cheeks and an outward appearance, at least, of better health.[12]
VOCs
Every time you prise open a can of gloss paint, squirt out some glue, daub metal polish on a photo frame or even shine your shoes, you’re releasing chemicals that make your head spin. You might not think of these things as poisons, but volatile organic compounds (VOCs), as they’re known, are a significant source of air pollution (‘volatile’ simply means they evaporate at everyday temperatures – so they pollute almost by definition). In some parts of the world, such as the European Union, household products like 21paints must now clearly label their volatile chemical content, so you can actively avoid VOCs, to a degree. Outdoors, most VOCs come from chemical leakages (remember the smell of fuel on the filling station forecourt?) and vehicle exhausts. But they also come from natural sources. That pine tree aroma you love so much? It comes from VOCs called terpenes, also used to make smelly household chemicals like turpentine.[13]
Particulates
It’s a mistake to think air pollution is just a mix of evil, dirty gases; it also contains microscopic solids and pinpoint drops of liquid. Look closely and you’ll see heavy metal deposits, industrial waste, soot from wildfires and wood burners, drifting rubbed-off flakes from car brakes and tyres, fly ash from municipal incinerators, construction and demolition dust and chemicals that magically form when other pollutants bump together. Exactly what your local air contains depends on where you are: in Egypt, for example, you’ll breathe in plenty of sand and organic, soil-like stuff blown in from the desert.
Swept along in the crowd of polluted air, these specks of dirt and tiny liquid droplets are called particulate matter (PM) or just particulates, and they come in varying shapes and sizes, commonly referred to with the suffix numbers 0.1, 1, 2.5 and 10. The coarse PM10s (less than 10 millionths of a metre in diameter – roughly ten times thinner than a thick human hair) and fine PM2.5s (less than 2.5 millionths of a metre – 40 times thinner than a hair) are mostly what we’ll meet in this book. Smaller particulates do more damage to our health because they can penetrate deeper into our lungs (bigger ones are less harmful because they’re heavier and fall to Earth faster, and also because they’re more likely to be trapped in our noses or throats).
22Fine PM2.5 particulates are the most dangerous kind of air pollution and pose a greater health risk for the world as a whole than alcohol, lack of exercise and over-salty diets. They’re currently responsible for around 4 million deaths a year from heart disease, stroke, lung cancer, lung disease and respiratory infections, and while it’s easy for many of us to improve our diets or take more exercise, air pollution is usually beyond our control.[14]
Figure 3. Particulates are specks of soot, dust and other things many times thinner than a human hair. PM10s are about 10 times thinner than a hair, PM2.5s are 40 times thinner and PM1s are 100 times thinner. PM0.1s, which we don’t meet much in this book, are 10 times smaller again. You could fit about 750 PM10s, 3,000 PM2.5s, 7,500 PM1s or 75,000 PM0.1s on the head of a pin.
And that’s just the start. To this little catalogue, we could add all sorts of bit-part extras found in vehicle exhausts, industrial gases from hundreds of different factory processes, household chemicals and sprays and many more. Some of these we overlook at great cost. Tobacco smoke alone contains over 7,000 chemicals, 70 of which cause cancer. Toxic lead, used in everything from ancient wine production to modern paint, is largely now under control, though its latent legacy will continue to poison us for decades. Ammonia produced by agriculture and farming is a particularly neglected pollutant that, through complex atmospheric 23chemistry, makes a major contribution to fine PM2.5 pollution. (One recent study estimated that a 50 per cent cut in ammonia emissions could save over 200,000 deaths a year in the 59 countries the researchers considered.) From acetaldehyde to xylenes, the US Environmental Protection Agency’s catalogue of hazardous air pollution lists no fewer than 182 different chemicals in our air that ‘present tangible hazard … to humans and other mammals’.[15]
Living in the lab
The main reason air pollution is such a complex and intractable issue is that it’s really multiple problems rolled into one. Each of its many components – every pollutant gas and particulate swirling around in the air – finds its way into your breath by a subtly different mix of chemistry and physics. It can be glib and misleading to refer to ‘pollution’ in general, when what we’re really talking about is hundreds or thousands of different chemicals all swooshing around together. Different types of pollution may have little in common, other than the one thing that matters most: the fact that they do some sort of harm to people or our world.
Having said that, the vast majority of the pollution we should worry about is produced by human activity. Outdoors, the main culprits are road traffic and other kinds of transportation (ships and planes), agriculture, fuel-burning power plants, industry and construction. Indoors, in developing countries, burning solid fuel for cooking and heating is by far the biggest issue – a growing problem in developed countries once again, thanks to the cosy fashion for huddling around wood burners in winter. Also in developed countries, because we obsess over clean and tidy homes, we have to worry about VOCs from things like paints, household cleaners, lubricants, polishes, air fresheners and more.
24One of the most interesting things about pollution is that it’s not static and unchanging: it has a mind of its own. Some years ago, I went to an eye-opening talk by a chemistry professor who specialised in studying the water pollution produced near highways. After name-checking all the toxic things that ‘run off’ roads into the hedges, verges, forests and rivers alongside, he revealed the astonishing fact that vehicle pollution also produces weed killers (herbicides). How could that be? There are no weed killers in cars. It turns out that the various chemicals flung out from car exhausts, tyres, brakes and fuel leaks, along with those scraped off the road surface, mix and react together spontaneously to produce a kind of second-generation pollution – in the form of herbicides – that is arguably even worse.
Similar things happen in the air. Pollution begets pollution – it’s born in the atmosphere as well as emitted directly. The classic example is smog; the thick, hazy fog that smothers cities choked with traffic. Cars don’t vent that smog from their tailpipes, but they do exhaust nitrogen oxides and VOCs (including evaporated petrol). Chemically activated by sunlight, these things produce reactive chemicals called radicals that create ground-level ozone and tiny organic particles, giving smog its hazy appearance. They also produce a lung and eye irritant called PAN (peroxyacyl nitrate), which helps to ferry smog over long distances. Interestingly, though we think of smog as something quintessentially human-made, it can also be formed spontaneously in the natural world. VOCs emitted by trees (terpenes) can react with nitrogen oxides and ozone to produce a natural, blue-coloured smog. This is how places like the Blue Ridge Mountains of Appalachia and the Blue Mountains of Australia get their names.[16]
So we’re not merely living and breathing in a world full of passive chemicals, but in an active, highly dynamic laboratory, 25where the things we fling into the atmosphere react together in dangerous and surprising ways.
Drawing the line
It’s not just the ‘quality’ of air pollution (what it contains) that should worry us, but also the quantity. If we’re going to call pollution a poison, the volume of gas or harmful particulates is crucially important. Does one molecule of ozone count as pollution, or one speck of soot from a diesel exhaust? What about a billion molecules or a trillion specks of soot? Is it the amount of pollution belching from cars that should worry us, or the toxic ‘dose’ our children receive? Where and how do we draw the lines? If your neighbour burns trash in her garden and fills your home with smoke once a year, is that punishable pollution? What if she does it once a month, or once a week? Does it matter how much trash she burns, or for how long?
One often overlooked point is the crucial difference between how much pollution things make (‘emissions’) and how much we breathe in over a period of time (‘exposure’). There’s an awful lot of focus on emissions in the news, but from a public health perspective exposure is what really counts. Praising ourselves for reducing emissions is certainly encouraging, but very far from the whole story; it’s like congratulating yourself on losing weight and ignoring the fact that you’re still morbidly obese. And reduced emissions don’t necessarily mean lower exposure, as US Environmental Protection Agency (EPA) scientist Lance Wallace tellingly pointed out in the 1980s. Back then, Wallace noted, petrol-fuelled car exhausts were producing about 82 per cent of the emissions of benzene (a toxic, carcinogenic VOC) in the environment around us, compared to just 0.1 per cent from 26cigarettes. A case for cleaning up cars? Not so fast! Because we spend so much time indoors, and sucking on a cigarette is a particularly effective way of delivering chemicals into the body, Wallace found that cigarettes caused 45 per cent of our exposure to benzene, while automobiles accounted for just 18 per cent. That’s one reason why the recent global crackdown on public smoking is such good news for people’s health.[17]
Figure 4. We assume most of the pollution we breathe in comes from chemicals expelled into the atmosphere by smokestacks and cars (emissions). When it comes to our health, however, what counts is the amount we inhale (exposure). Back in the 1980s, in the case of the toxic chemical benzene, much of people’s exposure (about 45 per cent) came from cigarettes, even though they made a tiny amount of total emissions. Much less exposure came from cars and industry, which are more tightly regulated. Figures from Wallace (1995), US Environmental Protection Agency.
The definition of pollution is a little bit arbitrary and always has been. In her classic 1960s book Purity and Danger, anthropologist Mary Douglas famously defined dirt as ‘matter out of place’ – an endlessly fascinating idea (one that stresses the importance of context), but not one many of us will instantly relate to. In everyday life, ‘pollution’ is our name for the exasperation we feel when a particular environmental nuisance (a local incinerator, a traffic-clogged high street or whatever it might be) exceeds limits 27we can tolerate. It’s complicated further by the fact that air pollution is highly dynamic, changing from day to day, year to year and season to season, and further still by our changing standards and social expectations. In the (relatively) eco-enlightened 21st century, none of us would be prepared put up with the kind of choking, smoky skies that were commonplace in the first part of the 20th century. But modern pollution is very different: the goalposts have moved, our standards have risen and we now know that pollution causes more harm, at lower ‘doses’, than previously believed. While there have been great gains in reducing some pollutant gases in some parts of the world (notably sulphur dioxide, thanks to the steady shift away from coal), others (notably nitrogen dioxide and ozone) are a cause for concern, and the health risks posed by low levels of particulates really only came to light in the 1990s. All of these factors help to explain one of the great contradictions that baffles many of us when it comes to understanding air pollution: even though the world seems cleaner now than in the past couple of hundred years, in some ways it’s more polluted than ever before.[18]
Vague and woolly definitions of ‘pollution’ are no use for practical purposes, so it’s obvious that we need formal, objectively scientific ways of measuring good or bad air quality. That’s fair, for the purposes of laws and regulations, and it gives us a decent way of charting our progress at cleaning up the air over time (though our changing standards and expectations make it harder). Typically, we figure out air quality by measuring the concentration of each pollutant (the amount in a certain volume of air), expressed either as so many parts per million or billion (ppm/ppb) or as a certain weight of pollutant in a volume of air (usually so many micrograms, or millionths of a gram of pollution per cubic metre of air, which we write in the form μg/m3). Parts per million 28is a revealing choice of measurement. In ordinary unpolluted air, we’d expect to find about 780,000 ppm of nitrogen (78 per cent) and about 209,000 ppm of oxygen (21 per cent), while carbon dioxide comes in at just 410 ppm, helium notches up 5 ppm and hydrogen just 0.5 ppm.
So where would you expect pollution to register on that scale? 10 per cent of the air? 5 per cent? 1 per cent? Typical amounts of nitrogen dioxide (one of our prime pollutants) in cities range between 0.01 to 0.05 ppm, while near very busy roads they’re about 10 times higher, reaching 0.5 ppm – roughly the same amount as natural levels of hydrogen. How do we visualise that? Barack Obama’s 2009 inauguration attracted a crowd of something like 2 million people. In theory, if the volume of that crowd represents the air, just one of those people represents a potentially harmful amount of nitrogen dioxide. In practice, it’s more complicated because (as we saw above) exposure is what really matters – so we have to factor in the time we’re breathing in pollution as well as the quantity. The same is true of particulates. The WHO’s target guideline for the amount of fine particulates (PM2.5) that people in cities breathe is an annual average of 10 millionths of a gram per cubic metre (technically written 10 μg/m3) – which is roughly the weight of a mosquito in a volume of air as big as a large armchair.3 One startling fact, often repeated in the scientific literature but generally missing from popular news reports, is that there are no 29safe lower limits below which PM2.5 particulate air pollution has no effect on our health (although the risk does decline). What all this tells us is very counterintuitive: our mental image of pollution might be thick black smoke, but invisibly minuscule concentrations of toxic gases and particulates – sometimes too small to see or smell – can do us actual harm.[20]
MEASURE FOR MEASURE
Back in the days when dirty clouds routinely drifted from smokestacks, the easiest way of measuring air quality was to hold up a series of cards, shaded from white to black, until you found the closest match. Invented by French professor Maximilien Ringelmann in 1888, this simple trick is still sometimes used today, though there are better ways to detect pollution now.
What about measuring the modern-style pollution you can’t even see? That’s the sort of challenge science geeks love to wrestle with. One simple method is to stick upside-down plastic tubes, filled with absorbent chemicals, on things like lampposts and road signs and leave them there soaking up the smog. Known as diffusion tubes, they sponge up gases, such as nitrogen dioxide, that seep (‘diffuse’) inside from the atmosphere; after a quick bit of lab analysis, they tell you the local concentration of the pollutant you’re interested in.
There are also natural ways of monitoring pollution; lichens have been used for this purpose since at least the 18th century. One French team has studied dirty air in Paris by sampling mosses in graveyards. An inspired ‘citizen science’ project called StrawbAIRies, run by Professor Roeland Samson at the University of Antwerp, recently gave out thousands of strawberry plants to people in six different countries. The eager volunteers measured traffic pollution by monitoring the size, shape and number of berries and pods the plants 30formed (presumably having controlled for variations in the local climate and growing conditions).
Although moss will react to pollution within ten seconds of exposure, diffusion tubes take a week to a month and strawberry plants take two months or longer, so methods like this don’t give a minute-by-minute reading of the pollution in your street. For that, you need decent scientific instruments – and that’s essentially why we don’t have good, real-time, air quality measurements for the entire world.
Having said that, with the notable exception of Africa and parts of the Western Pacific, air pollution is now monitored in one way or another in most urban areas. The WHO maintains the planet’s most comprehensive database of air quality, keeping rough tabs on the key pollutants in 4,300 cities in 108 countries. There are static air monitors in at least 5,000 urban and 800 rural sites in Europe alone.
What can you do if you want to probe the pollution where you live? People have been thinking of solutions for decades. Back in 1970, Popular Science magazine ran an article titled ‘Build your own air pollution tester’, with simple instructions for making a pollution monitor using a plastic bottle strapped to an old vacuum cleaner. Thankfully, science has moved on a bit since then; today, DIY air testing is easier than ever.
Throughout this book, I’ll be running some informal tests of the air I come across with a pocket-sized gadget called Plume Flow. It looks a little bit like an old-fashioned radio microphone, but it’s packed with laser-beam air sensors and sends real-time readings, via Bluetooth, to a smartphone app. Gadgets like this are great fun to use and give an interesting insight into everyday air pollution, although they obviously don’t take lab-quality measurements and you do have to treat their data with caution.
At the opposite end of the scientific scale, you can get all kinds of astonishing machines that use cutting-edge chemistry and physics to give instant readings of the different air pollutants in a particular 31place. There are drones with built-in, miniature air-sampling labs for sniffing air quality, in real time, high over a smoggy metropolis. One British lab even operates a wonderful electric truck called a Smogmobile, packed with air sensors – a kind of nose-on-wheels that can be driven through choking city traffic to give instant air readings. The most sensitive particle detectors use tiny optical fibres to detect PM0.1 particulates as small as 100 nanometres – half the size of a typical bacteria and about 1,000 times smaller than a human hair.[21]
Figure 5. The battery-powered Plume Flow air monitor (left) takes real-time measurements of PM1, PM2.5 and PM10 particulates, plus VOCs and NO2, and sends them to a phone app (right), which draws little maps of the pollution you encounter as you wander around.
Pollution at large
We’ve already seen that air pollution is active and dynamic; it can be useful to think of it having a finite lifetime (something that’s born, lives and dies) and a trajectory (something that starts in one place, travels through the air and ends up somewhere else – perhaps in many different places). Pollution begins life at a source of 32some kind, which could be anything from a chemical plant or a truck exhaust (in the case of human-caused pollution) to a forest fire or a volcano (in the natural world); it could come from a ‘point source’ (a single smokestack) or something much more diffuse (an entire forest or ocean). Once released, it might accumulate in the atmosphere or react in various ways to produce secondary pollution like smog, which lives its own polluted existence of birth, life and death. Or it could be slowly removed from the air by what are known in the trade as scavenging mechanisms. One example is the way sulphur dioxide from power plants reacts with oxygen in the air to make sulphur trioxide, which, in turn, reacts with rain, fog or other airborne water to produce the sulphuric acid that falls as acid rain. Dust and soot particles can disappear from the air when they smash and glue together, making heavier clumps that tumble to Earth, or crash into buildings and stick to the stone, blackening their faces. Different polluting gases and particulates have atmospheric lifetimes ranging from as a little as an hour (some VOCs), through 100 years or more (for some of the chlorofluorocarbons, CFCs, that damaged the ozone layer) up to 3,000 years (in the case of sulphur hexafluoride, a widely used industrial gas).[22]
Factories and power plants have smokestacks (very tall chimneys) designed to make dirty air drift and disperse – at least, in theory. In practice, because prevailing winds tend to blow their ‘plumes’ in the same direction, they often make pollution someone else’s problem. When it was first commissioned in 1972, one of the world’s tallest chimneys – the 380-metre (1,200-foot) high Superstack mounted on a copper-nickel metal smelting plant in Great Sudbury, Ontario – dramatically reduced toxic emissions in the immediate locality. Instead, it spread them over an area some 240 kilometres (150 miles) beyond. By the late 1990s, it was 33blowing out 52 tonnes of arsenic, 7 tonnes of cadmium, 147 tonnes of lead, 190 tonnes of nickel, 1,981 tonnes of particulates and 235,000 tonnes of sulphur dioxide each year, representing 20 per cent of the arsenic, 13 per cent of the lead and 30 per cent of the nickel emitted in the whole of North America. All that from just one chimney![23]
Even if there’s no wind to speed up the process, a small amount of one gas (like sulphur dioxide) released into the air will gradually spread apart through diffusion. Some pollutants stay in the air almost indefinitely, but most return to Earth as land or water pollution when something – maybe a human body, another kind of animal, a food crop, a tree, a building, a lake, an ocean – absorbs them.
Different kinds of pollution are born, live and die in very different ways, travel different distances by different means and meet their ends in different places, but Earth has only one atmosphere. Even if we sample and study the air we find in a single place – in the honking streets of Nairobi, perhaps, or the baked souks of Marrakesh – we’ll be looking at a mixture of pollution that, if we traced its trajectory from source to sink, we could variously describe as local, urban, regional, national or even global. As you’ll know very well if your neighbours are keen on garden bonfires, pollution is usually worst at the place where it’s made (the source), but local pollution, from a single, easily identified source, can also be easiest to tackle. At the opposite end of the spectrum, none of us can point to parts of the ozone hole we helped to destroy by spraying aerosol cans (and the harmful propellants inside them) in decades gone by. And the global damage we’re causing through climate change is so successfully diffused through the whole of humanity, past and present, that too few of us feel moved enough to make a difference.
34If the atmosphere is effectively one big blanket of gas wrapped tightly around the planet, you might wonder why air quality varies from country to country. If gases all diffuse eventually, why doesn’t all of Earth’s pollution simply average out over time, making the problem pretty much the same everywhere? The answer – perhaps surprisingly – is that air quality around the world doesn’t vary as much as you might think. Most countries suffer the modern mix of traffic, industry, agriculture and so on, so their pollution is often surprisingly similar. Even so, everywhere has its own subtle variations on the same basic theme: smoke from agriculture plays a big part in Delhi’s winter pollution, for example, while Beijing suffers wind-blown desert dust in the spring. Local climate, weather and geography also play an important part. Some of the world’s worst air pollution disasters, including the 1948 Donora incident in Pennsylvania and the Great London Smog of 1952 (which we’ll explore in Chapter 3), were greatly exacerbated by a weather-related phenomenon called temperature inversion, where smog smothers a city like a pillow pressed on a face.4
As we’ll see in the next chapter, air pollution is a truly global problem. We all make it; we all suffer from it – and it’s everyone’s problem to solve.
35
TESTING TESTING
Air freshener
Air fresheners might seem like your best friend when you sneak from the bathroom with a guilty look on your face, but the long list of chemicals printed on the can is a bit of a worry. The list of warnings is scary, too: the can in my bathroom includes ‘Use in a well-ventilated room’. What happens when you spray? According to my quick test with the Plume Flow air monitor, you’ll instantly bump volatile organic compounds (VOCs) up to eleven times their background level – and they’ll stay that way for a half hour or more. Why does that matter? A recent study by scientists at Seoul National University, Korea, argued air fresheners could have ‘potentially harmful health impacts, including sensory irritation, respiratory symptoms and dysfunction of the lungs’, but noted that ‘effects do not manifest for many years’.[24]
I think I’ll just open the window next time.
Figure 6.36 Chart shows: Y axis: Concentration of VOCs in parts per billion (ppb). X axis: time in minutes.
Table: A quick summary of six key types of air pollution. You might find it useful to bookmark this page and refer back to it in later chapters.
PollutantFormula/abbreviationCausesIndoors/OutdoorsHealth effectsOther effectsSulphur dioxideSO2Power plants, ships, home fires, wildfires, volcanoesIndoors/outdoorsBreathing difficulties (including asthma), cardiovascular diseaseAcid rain, crop damage, building erosionOzone (groundlevel)O3Secondary pollutant made indirectly by traffic, power plant emissions, refineriesMostly outdoorsLung disease and other respiratory illnessesSmog, crop damageNitrogen dioxideNO2Traffic, fuel combustion, wildfiresOutdoors/indoorsBreathing problems, including asthmaCrop damage, acid rain, smog, ozone formationCarbon monoxideCOTraffic, fuel combustion, smouldering firesOutdoors/indoorsBreathing problemsCrop damageVolatile organic compoundsVOCs (many separate chemical formulae)Vehicles, evaporating fuels, household chemicals, paints, tobacco smoke, wildfires and natural emissions from forestsOutdoors/indoorsMany (from dizziness to cancers)Ozone formationParticulates (including heavy metals)PM1, PM2.5, PM10 etc.Engines, factories, trash burning, agriculture, windblown dustOutdoors/indoorsMany (heart disease, stroke, cancers, respiratory illnesses, birth problems)Building erosion, crop damage371 An umbrella term for various ‘breathless’ conditions like emphysema, bronchitis and asthma, common in cigarette smokers.
2 In developing countries, choking smoke from cooking stoves is a major cause of cataracts and blindness.[3]
3 World Health Organization (WHO) experts have come up with guideline values for all the major pollutants. It’s important to note that these are not legally binding limits; nor are they ‘safe’ thresholds (below which we can say people are at no risk). Why have them, then? Three reasons: they provide concrete targets to help governments improve the air; they offer a way of comparing anywhere in the world to an objective standard; and they help us identify places where people are at most risk. Throughout this book, I’ll refer to these values as ‘WHO guidelines’.[19]
4 Temperature inversion is when a layer of warm air above a cold city acts as a lid on top of a toxic soup of pollution, holding it in place until the weather changes but sometimes, horrifically, killing people in the meantime. Inversions are a notable cause of the persistent smog in low-lying, coastal Los Angeles, which is surrounded by mountains that slow down air movements.
