How many times have you struggled to get to sleep because of a dazzling street light shining through your bedroom window? Or what about the countless hours you've spent sat in the office listening to the constant drone of sirens, cars and people outside?
It's surprising how easily we can get wound up by annoying sounds and bright lights, but for many of us, we've come to accept that these types of pollution are just part of modern life and something we have to live with - especially in big cities.
The situation is so dire in the UK that a survey found that 84% of Brits spend less than 10 minutes a day enjoying peace and quiet. It's also estimated that over 50% of the population are unable to clearly see the night sky because of the intense glare from artificial lighting.
What's even more worrying is the underestimated threat that noise and light pollution have on our health. Studies have linked intense noise to heart disease, high blood pressure and stress, while prolonged exposure to bright lights has been found to cause sleep deprivation and diabetes. This, combined with the well-known and deadly effect that air pollution can have on our physical wellbeing, means living in a modern, built-up city really can be a serious health hazard.
So, where is the world's most polluted city, and which population is the most exposed to a harmful concoction of sounds, lights, and dirty air? While London's pollution is pretty bad, how does it compare to that of New York's or Beijing's? We set out to answer these questions once and for all by looking at pollution data for 48 cities in 24 countries across the globe, on measures of air, noise and light pollution.
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The Methodology
To find out which city is the most polluted in the world, we analysed data on air, light, and noise pollution in 48 cities worldwide.
We took data from the World Health Organisation's (WHO) ambient (outdoor) air quality database on PM10 and PM2.5 for each city.
- PM10 is particulate matter found in the air of 10 micrometers in diameter or less
- PM2.5 is particulate matter found in the air of 2.5 micrometers in diameter or less, often described as fine particles
Particulate matter is a widespread air pollutant, consisting of a nasty mix of very fine solid and liquid particles suspended in the air. WHO identifies safe levels of PM10 as under 20 ug/m3, while safe levels of PM2.5 are under 10 ug/m3.
We used data from lightpollution.info to find out the level of artificial light pollution at night for each city, measured in μcd/m2. As a reference point, natural sky brightness is considered to be about 174 μcd/m2.
We used the Mimi Hearing Index to get noise pollution data, in which each city was given a noise pollution score between 0 and 2. The closer to 2, the more noisy a city is.
Each city was ranked on these measures of air, light, and noise pollution. The ranks were then combined to give an overall pollution score out of 100 for each city. The higher the score, the more polluted a city is.Any cities that were missing data were excluded from this study.
The 10 Most Polluted Cities
Cairo Dubbed the Most Polluted City in the World
If you love mummified Pharaohs, cotton bedsheets and the song 'Walk Like an Egyptian', then Cairo is the place for you. But if bright lights, filthy air and intense noise aren't your thing, it's probably best to stay away.
Our study named Cairo as the most polluted city in the world. On an average day, residents of the Egyptian capital breathe in air plagued with PM2.5 that's 11.7 times more dangerous than the recommended safe level by WHO. The city also has the 2nd highest levels of PM10 in the world, at 284 ug/m3 on average - 14.2 times over the safe limit.
Cairo is also loud. And we mean, really loud. The city is the 3rd most raucous metropolitan in the world with a score of 1.70, trailing behind only Guangzhou and Delhi. This will come as no surprise to Cairo's residents, however; a report by the Egyptian National Research Center found that noise pollution in the city reaches an average of 85 decibels everyday, which is like spending all day inside a factory.
Light pollution in Cairo is pretty bad too, with the city's metro area bathed in artificial light that's 85 times brighter than the natural sky (14,900 μcd/m2). It's no wonder, then, that our research named Cairo as the 3rd brightest city in the world, just behind Moscow and Chicago.
Pollution is (Shang)Hai in China
As you might expect, Chinese cities are some of the most polluted in the world, with Beijing (3rd), Guangzhou (6th) and Shanghai (7th) all making the top 10. Home to some of the largest metropolitan populations in our study (a mind-boggling 24.18 million people live in Shanghai), it's not hard to see why they're among the most polluted cities in the world, however.
The Chinese capital of Beijing has the worst air quality in China; measures of PM2.5 average 73 ug/m3 (that's 7.3 times over the safe level), while levels of PM10 exceed 90 ug/m3 on average (that's 4.6 times over the safe level).
It's not just Beijing that suffers from serious air pollution, however; our study also found that the air quality in Shanghai and Guangzhou is among the 10 worst in the world. Despite the Chinese Government declaring a "war on [air] pollution" in 2014, it seems that the world's 4th largest nation is still battling a serious "airpocalypse".
Our research found noise pollution to be a serious problem in China too, with Guangzhou being named the loudest city in the world with a score of 1.82. Beijing also ranked in the top 10 noisiest cities (6th), while Shanghai came in 12th. Surprisingly, light pollution isn't much of a problem in any of the Chinese cities in this study, with Beijing, Guangzhou and Shanghai ranking in the middle of the pack for night time brightness.
Moscow the Worst City in Europe for Pollution
Moscow has not only been named the 4th most polluted city in the world, but has won the title of the most polluted city in Europe, beating off stiff competition from the likes of Paris (9th), Barcelona (13th) and Rome (14th).
The Russian capital gives a pretty dire account of itself across the board, with its performance on noise and light pollution especially bad. Moscow is home to the 3rd brightest night sky in the world, with its street lights, homes and offices illuminating the sky to over 95 times its natural brightness (16,600 μcd/m2). Living in Moscow is also pretty loud, with the city ranking 11th overall for noise pollution (although renditions of " It's coming home " from heavily intoxicated English football fans during the World Cup probably pushed the city's noise levels even higher).
Comparatively, Moscow's air quality isn't quite as bad, with the city ranking around the middle of the list. Its levels of PM10 and PM2.5 are still much higher than what is considered safe by WHO, however, averaging 32 ug/m3 for PM10, and 20 ug/m3 for PM2.5 - significantly higher levels than in other major European cities such as Paris and London.
The 10 Least Polluted Cities
Zurich the Least Polluted City in the World
Having just been named the best country in Europe for vegetarians, Switzerland can now add having the world's least polluted city to its trophy cabinet. The beautiful Swiss metropolitan of Zurich landed in the bottom 5 for air, noise, and light pollution. It's no wonder that the Swiss enjoy the 2nd longest life expectancy in the world, when its largest city is a clean and peaceful urban paradise.
In terms of noise pollution, Zurich is the quietest city in the world with a score of 0.02, making it the perfect destination for light sleepers or those who just want a bit of tranquility. In fact, the Swiss take noise so seriously that they've even implemented 'Quiet Hours' in which residents are banned from making undue noise, such as mowing the lawn or playing loud music. Problems with light pollution are pretty much non-existent too, with the city being ranked the 2nd darkest in the world, just behind Oslo.
The air quality in the Swiss city is great also. Zurich's air has the 5th lowest density of PM2.5 (at 10 ug/m3 on average) and the 4th lowest amount of PM10 (at 16 ug/m3 on average) in the world, making its air over 11 times cleaner than Cairo's and well within WHO's safety level for air quality.
German Cities Leading the Way
A whopping 6 German metropolitans nabbed a spot in our list of the 10 least polluted cities in the world, with Munich (3rd) and Cologne (5th) featuring in the top 5. Each city scored well across all measures of noise, light and air pollution, suggesting that Germany is pretty good at keeping its pollution in check nationwide.
Munich came in the bottom 4 for both noise (4th) and light (3rd) pollution, while Cologne, Hamburg and Dusseldorf made the bottom 10 on both measures. The air quality in many of the German cities is also well within the safe level for PM10, with Munich, Cologne, Hamburg and Hanover having 20 ug/m3 or less of PM10 in the air. Where these metropolitans were let down, however, was on measures of PM2.5. All had high levels of the particulate matter, with Cologne and Stuttgart having the highest density of PM2.5 at 15 ug/m3 on average - 50% over the safe threshold.
Berlin (34th) and Frankfurt (32nd) were the only two German destinations not to make it into our list of the 10 least polluted cities in the world, mostly due to their poorer air quality. In particular, both Frankfurt and Berlin are among the 10 worst cities for levels of PM10 in the air, in 6th and 10th place respectively.
The Story in the UK
London Worst in the UK for Pollution
Ha! No way! I can't believe it! Said no one, ever.
A result that's as predictable as the England football squad failing to make it through to the World Cup final, our study has named London as the most polluted city in the UK. Although the English capital didn't fare too badly in the overall world ranking (coming in at 23rd place), its pollution levels are still much worse than those of the UK's sprawling northerly cities, such as Manchester (28th) and Liverpool (33rd).
London scored significantly worse than the other UK cities on measures of noise and light pollution. Unsurprising really, when its population has reached over 8 million - more than 3 times the size of Manchester, Birmingham, Liverpool and Glasgow combined.
The Big Smoke is more than 67 times brighter than the natural sky (11,100 μcd/m2), placing it in the top 10 worst cities in the world for light pollution. The 24-hour buzz of sirens, traffic and party-goers also makes it a pretty loud place to live; London is the 19th noisiest city in the world, 2 places higher than Birmingham, and 11 places higher than Liverpool.
In terms of London's air quality, the amount of PM10 found in the city's air is much higher than that found in other UK cities. Averaging 23 ug/m3 - more than 10% over the safe level established by WHO - London's level of PM10 is worse than Manchester's, Birmingham's and Glasgow's. Surprisingly, Liverpool recorded higher levels of PM10 than London, at 36 ug/m3. The capital's PM2.5 levels also tell a similar story, with Liverpool being the only UK city to record the same high levels of PM2.5 as the capital, averaging 12 ug/m3.
Famous for the tikka masala curry (no, really), the age-old rivalry between Celtic and Rangers football clubs, and the 2003 Pop Idol winner Michelle McMannus, Glasgow can now gain notoriety for being the least polluted city in the UK. Its pollution levels are so low, in fact, that Glasgow just missed out on placing in the top 10 least polluted cities in the world, coming behind Sydney.
Residents of Scotland's largest city enjoy filling their lungs with clean air. Measures of PM10 and PM2.5 in Glasgow are well within WHO's safety guidelines for air quality, averaging 12 ug/m3 and 8 ug/m3 respectively, making its air less polluted than all the other UK cities in this study.
Glasgow also outperforms its UK rivals on measures of noise and light pollution. The city is the 15th quietest in the world with a score of 0.72, while its artificial brightness is around 50% dimmer than that of London's. Liverpool was the only UK city found to have lower levels of noise and light pollution than Glasgow.
To Round Up
So there you have it: Zurich is the cleanest, quietest and least dazzling (in a good way, of course) city in the world, while if you're travelling to Cairo, it's probably best to pack a pollution mask, ear protectors and a pair of sunglasses, unless you want to return with sleep deprivation, tinnitus and lungs full of dust.
If you liked this story, you should check out the rest of our blog.
If you'd like the full list of rankings, please email rachel.thompson@mvfglobal.com