Sources:CentreforResearchonEnergyandCleanAir;TomTom;TheEconomist *Afteradjustingforweatherconditions
Nitrogen-dioxidepollution*in 12 citiesthatlockeddowninMarch 2020
Startoflockdown=100,30-daymovingaverage
Nitrogen-dioxidepollution*v trafficcongestion
Startoflockdown=100,weeklyreadingsin 12 cities
Deathsavertedfromdeclineinairpollution*
January1sttoAugust25th,estimate
→Airpollutionfellprecipitouslyaftercitieslockeddown,buthassincerebounded
↓Per100,000people ↓To t a l
20
40
60
80
100
120
140
Jan Feb Mar Apr May Jun Jul Aug
Paris
Bangalore
Rome
Delhi
London
NewYorkCity
Santiago
2 LosAngeles
42 Brussels
31 Warsaw
23 Berlin
18 Santiago
29 Madrid
12 NewYorkCity
0 2,000 4,000
41 Delhi 4,644
30 Bangalore 1,543
69 Pa r i s 1,486
49 Rome 1,259
16 London 1,227
0
50
100
150
0 50 100 150 200
Road-trafficcongestion
Delhi,theweek
lockdownbegan
Delhi,a
monthlater
TheEconomistSeptember 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 creaestimates 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. 7
Air pollution is nearing pre-covid
levels, boding ill for respiratory health
Blue skies
turn grey
Graphic detailAir pollution