Everything you should know about air pollution
It isn’t just cars that fill our urban centres with particles. Damian Carrington explains why air pollution is on the rise – and what we can do about it
Why is air pollution such a fast-growing concern?
Nothing is more vital to life than breathing: in an average lifetime, about 250m litres of air passes through your lungs. Yet walk along a busy city street and you will inhale something like 20m harmful particles in a single lungful.
Toxic air is now the biggest environmental risk of early death, responsible for one in nine of all fatalities. It kills 7m people a year, far more than HIV, tuberculosis and malaria combined. Dr Maria Neira, the World Health Organisation director with responsibility for air pollution, is blunt: “It is a global public health emergency.”
How much does it cost us?
The lost lives and ill health caused are also a colossal economic burden: £173bn ($225bn) in lost labour income in 2013, or $5.11 tn per year (about $1m a minute), if welfare losses are added in, according to a 2016 World Bank report, which called the figure “a sobering wake-up call”. Air pollution is getting worse in the developing world and, while it is getting better in some developed nations, our knowledge of how comprehensively it damages our bodies and minds is growing even faster.
Dirty air has been with us for centuries – previously, we simply lived with it – and no one has yet had air pollution as a cause of death on their death certificate. It is only in recent decades that the damage to health has become clear, and in the last few years that the crisis has received widespread attention, thanks to research revelations, government legal defeats and the Volkswagen diesel scandal.
But there is a silver lining to air pollution’s cloud of smog: action to cut it not only brings immediate benefits but also helps fight climate change in the longer term.
Who does it affect?
Over 90% of the world’s population lives in places where air pollution is above WHO guidelines. It is worst in south and east Asia, where most of humanity lives, thanks to traffic, dirty industry and the open burning of waste. India has almost half of the top 50 most polluted cities in the world, China has eight and Iran has three. Africa is highly polluted but little measured: in 2015, Paris had three times more monitoring stations than the entire continent. But air pollution affects rich nations.
“The trends are positive if we look at the last 50 years, but it depends how many deaths are you ready to accept,” says Neira. “We still have 500,000 deaths in Europe [per year] and this is totally unacceptable.” Children’s developing bodies are uniquely vulnerable, but 300 million live in places where toxic fumes are six times higher than international guidelines recommend.
Are there different types of air pollution?
Yes. The most damaging but best understood are tiny particles (PM2.5s), which harm the lungs and enter the bloodstream. They are increasingly thought to enter vital organs, including the brain, and have been shown to reach the liver, spleen, kidneys and testes in lab animals. The particles can be made of black carbon, nitrates, sulphates, ammonia or mineral dust. Most are produced by burning fossil fuels or wood, for transport, heating, power plants and industry.
In some countries, improvements have been made to coal-fired power stations and cars, but other sources of pollution lag behind. Farming is one source, with ammonia from livestock manure and fertilisers blowing into cities and forming particles, particularly in the spring. Nitrogen dioxide, produced by diesel vehicles, not only forms particles but is now known to cause harm when breathed as a gas. It is still illegally high in much of urban Britain, where it results in about 23,500 early deaths.
Other pollutants include sulphur dioxide, which is still very high in ship and aviation fuels. Groundlevel ozone, which forms on sunny days, harms people as well as crops: 7-12% of the global wheat crop is estimated to be lost in this way; in India, crop yields are reduced by 28%.
There are some natural sources, such as dust storms and smoke from forest fires, but human-caused pollution far exceeds these. Outdoor air pollution causes 4.2 million early deaths, says the WHO.
What about indoors?
This is also a huge killer, causing 3.8 million early deaths. Half the world’s population cook on open fires with “dirty” fuels such as wood, dung and
A burning issue
The impact of wood-burners on western city air has surprised researchers. “It has crept under the radar,” says Prof Gary Fuller, at King’s College London.
As many as 1.5m stoves have been sold in the UK, and 40% of particles in British cities are from wood burning, more than double than the emissions from vehicles. The same rise has been seen in France, Germany and Belgium, while Australia and parts of the US and Canada have had similar issues. In New Zealand, wood burners spew out up to 90% of particle pollution.
In many European cities people burn waste wood, often covered in lead paint, putting toxic metal into the air. But government action is biting. Montreal has banned all but the most modern and least polluting stoves and old, smoky burners are being scrapped in Crested Butte, Colorado. charcoal. Kerosene in wick lamps also produces dangerous smoke. However, more people are getting access to better fuels and stoves. Among farmers in Xuanwei in China, lung cancer cases fell by 40% when they switched to using stoves with chimneys in their homes. But with the global population rising, the number of people exposed to indoor pollution is not falling.
What harm does air pollution do?
It is easier to ask what harm does air pollution not do. Research links toxic air not only to almost every part of the body, but also the mind.
The landmark research linking air pollution to lung diseases, heart attacks and strokes – the Harvard six cities study – was first published in 1993. Since then dirty air has been linked to many conditions, such as diabetes. Air pollution contributed to 3.2m new cases of this illness in 2016, according to one study. Kidney disease appears to be influenced by air pollution, as does Alzheimer’s. Skin ages more rapidly in dirty air.
The research on babies and children is particularly worrying. A large recent study found toxic air significantly increases the risk of low birth weight, leading to lifelong damage to health.
Millions of premature births may be linked to air pollution; another study makes the connection to birth defects and another to cot deaths. The first direct evidence of pollution particles in mothers’ placentas has also been revealed.
“It is a worrying problem – there is a massive association between air pollution a mother breathes in and the effect it has on the foetus,” said the lead researcher.
As children grow, asthma and stunted lung growth has a serious impact, but pollution also affects the
Pollution and the brain
A major study published in August Au 2018 found that air pollution causes a “huge” reduction in intelligence. For the worst affected category, older men, the damage is equivalent having spent fewer few years in education, possibly due to inflammation of the brain. The average damage across men a and women of all ages was one lost year of learning. Recent research also links air pollution to mental illness, particularly the risk of suicide. A study in Hong Kong found spikes in toxic air correlated with “extremely high mortality” in people with mental disorders. The same link was was found in Belgium, even when pollution was below belo legal limits. . Similar results have ha been found in Salt Lake City, Utah, South Korea and, in people under 30, in Tokyo. Research in London found peopple people over 50 in areas with the highest nitrogen dioxide pollution had a 40% greater risk of developing dementia. ability to learn in school and even the risk of teenage delinquency.
The estimated annual death toll of 7 million is an underestimation, as it only includes particle pollution and the five most firmly linked causes of death, such as heart attacks. Early estimates using improved models suggest a total figure of 9 million from particle pollution. Even this is only “the tip of the iceberg”, according to researchers. Exposure to air pollution is likely to damage the health of almost everyone.
The WHO is clear: “The burden of disease from [outdoor] air pollution is expected to greatly increase.”
Can I protect myself?
Masks are commonly advertised, but experts say they are of limited use unless they are airtight.
Giant towers, street-side benches and living, green walls have all been proposed to filter dirty air. A new bus aims to filter air as it travels around Southampton. Pollution-monitoring apps and walking routes that keep pedestrians away from the filthiest roads are useful. Trees can help, unless they block the breezes that blow pollution away.
People in cars are often exposed to more pollution than those outside, as fumes become trapped in the cabin. Closing the air circulation in your car before hitting the city centre is a good idea.
There is also some evidence that omega oils and vitamin B may offer some protection against the damage caused by air pollution.
Isn’t that treating the symptom, not the cause?
Yes. The only practical way to tackle the global health emergency is to cut levels of pollution at source. There is an ethical angle too, says Prof Gary Fuller, at Kings College London: “Morally it is not right to make the victims change their behaviour, instead of the culprits.”
Poorer people are also most exposed to air pollution. “There are huge injustices at the heart of the air pollution problem,”’ says Fuller. “By using our air to dispose of their waste, polluters are destroying a shared resource and avoiding the full cost of their actions.”
India has almost half of the top 50 most polluted cities in the world, China has eight and Iran has three
UK PM2.5 polluters in kilotonnes, 2016