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Air pollution fell precipitously after cities locked down, but has since rebounded

↓

Total

↓

Per 100,000 people

20

40

60

80

100

120

140

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Paris

Bangalore

Rome

Delhi

London

New York City

Santiago

2

Los Angeles

42

Brussels

31

Warsaw

23

Berlin

18

Santiago

29

Madrid

12

New York City

0

2,000

4,000

41

Delhi

4,644

30

Bangalore

1,543

69

Paris

1,486

49

Rome

1,259

16

London

1,227

0

50

100

150

0

50

100

150

200

Road-traffic congestion

Delhi, the week

lockdown began

Delhi, a

month later

The Economist

September 5th 2020

77

C

ovid-19 is not

all bad, as any city-

dweller who stepped outside this year

will have seen. The virus has killed hun-

dreds of thousands of people and decimat-

ed economies around the world. But as 

gdp

has fallen so has air pollution. This spring

marked the first time in decades that resi-

dents of Jalandhar in northern India were

able to see the snow-capped Himalayan

mountains, 160km (100 miles) away.

One particularly common pollutant is

nitrogen dioxide (

NO

2

). The World Health

Organisation (

who

) reckons that 

NO

2

lev-

els above 40 micrograms in every cubic

metre of air (40μg/m

3

) are harmful to peo-

ple. In Delhi, one of the world’s most pol-

luted big cities, 

NO

2

fell sharply after the

city imposed its lockdown, from 46μg/m

3

in March to 17μg/m

3

in early April. Similar-

ly, 

NO

2

levels in London fell from 36μg/m

3

in March to 24μg/m

3

two weeks later.

Air-pollution levels do not depend on

human activity alone—weather conditions

such as wind speed, rainfall and humidity

matter, too. The Centre for Research on En-

ergy and Clean Air (

crea

), a think-tank, has

produced a model which takes these fac-

tors into account to gauge the impact co-

vid-19 has had on air-pollution levels in 12

big cities around the world. They found

that 

NO

2

levels fell by about 27% ten days

after governments issued stay-at-home or-

ders, compared with the same period in

2017-19. Levels of particulate matter less

than 2.5 micrometres wide (

PM2.5

), which

are also harmful to health, declined by an

average of about 5% in a group of 12 big cit-

ies in which data are readily available.

The health benefits of cleaner air are

profound. The 

who

reckons that about

90% of the world’s population live in

places where air quality falls short of its

standards. They estimate that 4.2m people

died prematurely from diseases related to

air pollution, such as respiratory-tract in-

fections and lung cancer, in 2016 alone, in-

cluding 290,000 children. Millions more

suffer from chronic health problems.

The 

crea

estimates that improved air

quality since the covid-19 pandemic began

has saved about 15,000 lives in 12 big cities.

In Delhi, around 4,600 people have es-

caped death due to air pollution—roughly

as many as are known to have died from co-

vid-19, although the disease’s true tally is

probably higher and still rising.

As people return from summer holidays

in the northern hemisphere and econo-

mies begin to recover, air pollution is near-

ing pre-pandemic levels. Although people

are still wary of using public transport,

they appear to have fewer reservations

about driving cars themselves—data from

TomTom, a location-tech firm, show that

congestion in big cities has just about re-

turned to pre-covid levels. This increase in

pollution will be deadly, especially to those

who suffer from severe asthma, who are

also vulnerable to covid-19. 

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