It’s an all too common sight. Photographs of megacities, usually in India or China, cast in a yellow-grey haze, their tallest buildings obscured by gritty clouds. Scientists refer to these specks of pollutants as ‘fine particulate matter’. They divide the particles into PM2.5 (2.5 micrometres or less in diameter) and PM10 (ten micrometres or less in diameter).
The World Health Organization (WHO) recommends a maximum annual mean level for PM10 and PM2.5 of 20 and ten micrograms per cubic metre respectively. Its most recent release of air quality data, covering 4,300 towns and cities from 108 countries, reveals that the air in most places exceeds this limit, sometimes by more than 15 times. The bleak conclusion is that nine out of ten people worldwide are breathing polluted air and more than half of the global urban population lives in cities that exceed the recommended levels of fine particulate matter by 2.5 times or more.
Fine particles have deadly potential. They penetrate deep into the lungs and cardiovascular system, leading to strokes, heart disease, lung cancer, chronic obstructive pulmonary diseases and respiratory infections, including pneumonia. Unsurprisingly, lower-income towns and cities are the worst hit.
According to the WHO, the poorest air quality is found in the eastern Mediterranean and Africa, followed by Southeast Asian countries. It estimates that around seven million people die every year from exposure to fine particles and that 90 per cent of total air pollution-related deaths happen in low and middle-income countries, mainly in Asia and Africa.
The origin of these particles goes some way to explaining their prevalence in poorer countries. Outdoor particulate matter largely comes from industry, agriculture, transport and coal-fired power plants. As richer countries transition to cleaner fuel supplies, countries like India are left importing cheap but noxious fuels such as petroleum coke – the thick black residue left at the bottom of the barrel during crude oil refining.
Indoor air pollution is also a big killer and is mainly caused by inadequate cooking facilities. People cooking on open fires and stoves without chimneys usually make use of basic fuels such as wood, animal dung, crop waste and coal. These emit smoke clogged with soot particles and dust. Combined with poor ventilation its a deadly practice. The WHO estimates that household air pollution caused 3.8 million deaths in 2016.
Dr Tedros Adhanom Ghebreyesus, WHO’s director general said: ‘It is unacceptable that over three billion people – most of them women and children – are still breathing deadly smoke every day from using polluting stoves and fuels in their homes. If we don’t take urgent action on air pollution, we will never come close to achieving sustainable development.’
Of all the regions covered by the data, India fares particularly badly. Fourteen of India’s cities feature among the world’s 20 most polluted (though it should be noted this isn’t a definitive ranking due to different methods and dates of data collection).
One of the worst affected is the city of Kanpur with a PM2.5 concentration of 173 micrograms per cubic metre. The second largest city in the state of Uttar Pradesh, Kanpur is situated on the banks of the chronically polluted Ganges River and is famous for chemical-spewing leather tanneries. Other cities with extremely high levels of air pollution include Peshawar and Rawalpindi in Pakistan and the industrial city of Al Jubail in Saudi Arabia.
As megacities go, the air breathed by the residents of Delhi and Cairo is by the far the most toxic. Both cities have average PM10 levels of more than ten times the WHO guidelines. In Cairo, this is largely down to the two million cars that clog the roads every day, as well as emissions from factories and from farmers burning leftover rice husks just outside the city. Dhaka and Mumbai come in at around five times the recommended level, as does Beijing, notorious for its thick grey smog.
Though Chinese cities are far from smog-free, recent government efforts to reverse the trend of high air pollution seem to be working. Measures have included a requirement for higher-quality gasoline and diesel for vehicles, a cap on the number of private cars that can be sold in a year and, crucially, plans to close or cancel over 100 coal-fired power plants.
The WHO has said it would now like to see measures such as this adopted in India. Speaking to Reuters, Maria Neira, WHO’s head of public health said: ‘There was a big step at the government level [in China] declaring war on air pollution. One of the reasons for that is that the health argument was very strongly presented, and the fact that citizens were really breathing air that was totally unacceptable.
‘We would be very happy to see a similar movement now in India, which is one of the countries for which we are particularly concerned. Although there are good initiatives which can be put in place quickly, still the levels are very high and we would like to see a similar decision and leadership.’
More positively, the WHO points to a number of productive initiatives. In particular, it highlights the Pradhan Mantri Ujjwala Yojana Scheme in India which has provided 37 million women with free gas connections for the home. It also notes that more than 1,000 additional cities have been added to the database since 2016, reasoning that a problem can only be solved if it’s acknowledged.
However, some countries still don’t monitor particulate matter at all and many of these places are likely to be badly affected as a result. This is a particular issue in Africa where the WHO only has data for eight of the 47 countries in the region.
Matthew Evans, a professor of atmospheric chemistry modelling at York University thinks that the low level of monitoring in Africa comes down to the way resources have historically been allocated. ‘I just don’t think the atmospheric issue has come up as significant,’ he says. ‘When countries have decided how to allocate resources, they’ve allocated to the things that have been directly in front of their faces – poor health, environmentally transmitted diseases, poor water.’
Most parts of Africa face the same man-made challenges as other lower-income countries but they also have to contend with natural sources of air pollution. The Sahara blows vast amounts of dust into neighbouring countries while in central and west Africa the seasonal burning of trees produces huge quantities of smoke.
It’s a problem that, as yet, has no real solution. ‘Trying to control the desert requires a very different kind of toolkit than the one you need to control emissions from cars or cooking,’ says Evans. ‘This is an area where European, North American and to some extent Chinese scientists, haven’t developed a toolkit because they’re not problems that they face.’
Here in the UK, the levels of fine particles in the air are nowhere near the dizzying heights of the world’s most polluted cities. What’s more, levels have been falling in a number of places, including London and Sheffield. In the capital, levels of PM2.5 fell from 17 to 11 micrograms between 2013 and 2015. Nevertheless, 31 cities in the UK still exceed recommended levels of PM2.5. According to environmental charity, Friends of the Earth, there are still 40,000 premature deaths in the UK linked to air pollution.
The next step for the WHO is to continue securing valuable data and to work with the worst affected countries. Pierpaolo Mudu, a technical officer at the organisation, explains that some of the data and information received from countries doesn’t accurately reflect the source of air pollution. ‘We are now pushing for source-specific studies, so we can see where the source of pollution comes from,’ he says. ‘This is very important as you can’t have efficient interventions without understanding the source of pollution.’
As for helping countries to reduce emissions, it isn’t seen as being such a simple task. Each country needs to be treated on a case-by-case basis depending on the main source of pollution in that region. Nevertheless, reducing fumes from inadequate cooking facilities and cutting down car emissions remain fundamental goals that apply across the globe. Mudu says the WHO is also working to introduce industrial technology widely used in the West into countries that rely on machinery and techniques that are less clean.
It will be a long and dirty road. If the WHO data shows anything, it’s that air pollution is a global problem. Rich or poor, almost all countries are affected in some way. What’s also apparent is that, as is so often the case, poorer nations suffer the gravest consequences.
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