Pollution on the Paris Metro: the French capital's dirtiest spots are all underground

Don't inhale. Image: Getty.

Where do you think are the most polluted places in a city? On the busiest streets, perhaps? Or near sites of heavy industry?

In Paris, at least, the answer is "neither". A study carried out by French health watchdog ANSES has found that the most clogged air in the city is actually under its streets: on the Paris Metro. The air underground, the paper finds, has the highest levels of PM-10 particulates (which means air particles of up to 10 micrograms in diameter) than anywhere at street level.

According to Pangea Today, which drew on information in French paper Le Monde, the particulate levels underground were at least double those on Paris's streets. Sometimes, they were up to 40 times as high: 

While the average concentration rate of PM10 outside is of 25 to 30 µg/m3, the average rate at underground platforms is of 70 to 120 µg/m3, with the peak rate reaching as much as 1,000 µg/m3 between 2 and 5 a.m.

Several studies have found that London's Underground system, too, is very polluted – particularly the deeper Piccadilly, Northern, Bakerloo and Central lines. 

So why the underground fug? In both Paris and London, the causes are roughly the same. Particulate matter enters through station entrances and ventilation shafts, and then, since it's heavier than the air around it, is trapped underground. The friction caused by older braking system can also generate airborne particles.

All this is obviously worrying for metro passengers, but they're only exposed to the bad air for short stretches of time. Drivers and maintenance and station workers, meanwhile, spend a good portion of their day underground. For them, these pollutants represent a serious health hazard – and it's largely for their sake that metro networks should invest in modern braking systems and better air filtration. 


Covid-19 is highlighting cities' unequal access to green space

In the UK, Londoners are most likely to rely on their local park for green space, and have the best access to parks. (Leon Neal/Getty Images)

As coronavirus lockdowns ease, people are flooding back to parks – but not everyone has easy access to green space in their city.

Statistics from Google show that park attendance in countries across the globe has shot up as people have been allowed to move around their cities again.

This is especially true in urban areas, where densely populated neighbourhoods limit the size of private green space – meaning residents have to go to the park to get in touch with nature. Readers from England can use our interactive tool below to find out how much green space people have access to in their area, and how it compares to the rest of the country.


Prime Minister Boris Johnson’s announcement Monday that people are allowed to mingle in parks and gardens with groups of up to six people was partially following what people were doing already.

Data from mobile phones show people have been returning to parks across the UK, and also across Europe, as weather improves and lockdown eases.

People have been returning to parks across the world

Stay-at-home requirements were eased in Italy on 4 May, which led to a flood of people returning to parks.

France eased restrictions on 1 May, and the UK eased up slightly on 13 May, allowing people to sit down in public places so long as they remain socially distanced.

Other countries have seen park attendance rise without major easing of lockdown – including Canada, Spain, and the US (although states there have individual rules and some have eased restrictions).

In some countries, people never really stopped going to parks.

Authorities in the Netherlands and Germany were not as strict as other countries about their citizens visiting local parks during lockdown, while Sweden has famously been avoiding placing many restrictions on people’s daily lives.

There is a growing body of evidence to suggest that access to green space has major benefits for public health.

A recent study by researchers at the University of Exeter found that spending time in the garden is linked to similar benefits for health and wellbeing as living in wealthy areas.

People with access to a private garden also had higher psychological wellbeing, and those with an outdoor space such as a yard were more likely to meet physical activity guidelines than those without access to outdoor space. 

Separate UK research has found that living with a regular view of a green space provides health benefits worth £300 per person per year.

Access is not shared equally, however, which has important implications for equality under lockdown, and the spread of disease.

Statistics from the UK show that one in eight households has no garden, making access to parks more important.

There is a geographic inequality here. Londoners, who have the least access to private gardens, are most likely to rely on their local park for green space, and have the best access to parks. 

However the high population in the capital means that on the whole, green space per person is lower – an issue for people living in densely populated cities everywhere.

There is also an occupational inequality.

Those on low pay – including in what are statistically classed as “semi-skilled” and “unskilled” manual occupations, casual workers and those who are unemployed – are almost three times as likely as those in managerial, administrative, professional occupations to be without a garden, meaning they rely more heavily on their local park.

Britain’s parks and fields are also at significant risk of development, according to new research by the Fields in Trust charity, which shows the number of people living further than a 10-minute walk from a public park rising by 5% over the next five years. That loss of green spaces is likely to impact disadvantaged communities the most, the researchers say.

This is borne out by looking at the parts of the country that have private gardens.

The least deprived areas have the largest gardens

Though the relationship is not crystal clear, it shows at the top end: Those living in the least deprived areas have the largest private green space.

Although the risk of catching coronavirus is lower outdoors, spending time in parks among other people is undoubtedly more risky when it comes to transmitting or catching the virus than spending time in your own outdoor space. 

Access to green space is therefore another example – along with the ability to work from home and death rates – of how the burden of the pandemic has not been equally shouldered by all.

Michael Goodier is a data reporter at New Statesman Media Group, and Josh Rayman is a graphics and data visualisation developer at New Statesman Media Group.