Living in a highly polluted area may increase the risk of dementia by as much as 40 per cent, a new study has suggested. The research found an association between the neurodegenerative condition and exposure to nitrogen dioxide and microscopic particles known as PM2.5.
Unfortunately for Londoners, pollution is a persistent problem in the UK capital. Two separate high pollution warnings were issued over the summer, with vulnerable people advised to avoid strenuous physical exercise, while a 2017 report suggested air quality in every area of the capital was regularly breaching World Health Organisation guidelines.
The WHO guidelines suggest a mean PM2.5 target of 25 micrograms per cubic metre over a 24-hour period, with an annual mean of 10. The highest reading in London right now – at Old Street – is 81μg/m3, while the city’s annual mean is 12.
That puts it behind a clutch of world capitals. Of those countries for which the WHO has data, Madrid, Oslo, Dublin, Montevideo, Helsinki, Ottawa, Washington DC and Canberra perform better than London. Top of the table are Stockholm and Tallinn, with an annual mean of 5μg/m3, followed by Edinburgh, with 6. It does fare better than Paris and Berlin, however (both 16), and is on a par with Lisbon (also 12).
Stockholm was the first city to be crowned European Green Capital in 2010 – and it clearly hasn’t rested on its laurels. Since taking the accolade, the Swedish capital has continued to forge ahead with eco initiatives and has successfully slashed carbon emissions by 25 per cent since the Nineties. The city aims to be fossil-fuel free by 2050, a target it hopes to achieve by improving public transport, slashing waste and increasing biodiversity, among other things. The city also has a strong culture of cycling, which has kept many residents out of cars.
Medieval Tallinn – with its imposing city walls and narrow cobbled streets – was not built with motor vehicles in mind. Driving around the ancient city centre is impractical, which has largely kept cars away. Add to that the city’s bountiful green spaces and breezy coastal setting and you have the ingredients for one of the least polluted cities in the world.
Capital cities less polluted than London (annual mean, PM2.5)
London = 12μg/m3
- Madrid – 10
- Oslo – 9
- Dublin – 9
- Montevideo – 8
- Helsinki – 7
- Ottawa – 7
- Canberra – 7
- Washington DC – 7
- Edinburgh – 6
- Tallinn – 5
- Stockholm – 5
PM2.5 refers to fine particles (2.5 micrometres or smaller in diameter), which are produced by combustion, including motor vehicles, power plants, forest fires, and some industrial processes.
The WHO also records levels of coarser dust particles (PM10), the result of crushing or grinding operations and dust stirred up by vehicles. For this metric, London’s air is dirtier than at least 17 major capitals, including Vienna, Amsterdam, Dublin, Wellington and Cardiff.
Capital cities less polluted than London (annual mean, PM10)
London = 23μg/m3
- Vienna – 22
- Helsinki – 21
- Amsterdam – 21
- Luxembourg City – 20
- Malé – 20
- Stockholm – 20
- Bern – 19
- Madrid – 19
- Cardiff – 19
- Oslo – 18
- Monaco – 17
- Reykjavik – 16
- Dublin – 13
- Port Louis – 13
- Wellington – 13
- Tallinn – 12
- Edinburgh – 11
Which is the world’s most polluted city?
In terms of PM2.5, no city has a higher average mean than Peshawar – it is 540μg/m3, according to the WHO. Rawalpindi (Pakistan), Mazar-E Sharif (Afghanistan), Hamad Town (Bahrain) and Delhi (India) complete the bottom five.
Last year pollution in Delhi, which typically spikes during winter, hit almost 30 times the World Health Organisation’s (WHO) safe limits, with the concentration of PM2.5 topping 700μg/m3.
Nowhere on Earth is more polluted right now than Monclova in Mexico, however, where the figure is 869.
And the world’s most polluted country?
Pinpointing them is a little more problematic. The WHO tracks air quality at 1,622 locations in 92 countries – but all are urban areas. So while Pakistan, Egypt and Mongolia are among the most polluted countries according to the map below, this only refers to pollution in its cities. Air quality in the Karakoram mountain range or the Gobi Desert will, of course, be pristine. Similarly, Russia appears to be among the worst performing countries – but its ranking is based only on air quality in Moscow.
Of the 92 countries to feature, Australia has the least polluted urban areas, followed by Brunei and New Zealand. Estonia is Europe’s top performing nation, followed by Finland and Iceland. The UK just misses out on the top 20, coming 21st.