15 January 2022 | New Scientist | 19Health
Drop in child asthma cases linked to pollution
Heavy traffic
on a street
in New Delhi,
IndiaABOUT 1 in 12 new child asthma
cases worldwide are associated
with exposure to a toxic gas
released by diesel vehicles,
according to a new estimate
showing a drop due to cleaner air.
Breathing high levels of
nitrogen dioxide (NO2) has been
previously linked with triggering
and exacerbating asthma in
childhood. The evidence is now
considered strong enough that
in 2020, a UK coroner ruled
that exposure to the pollutant
contributed to the death of
9-year-old Ella Kissi-Debrah.
Susan Anenberg at George
Washington University in
Washington DC and her colleagues
estimate that 1.85 million new
childhood asthma cases were
linked with the gas in 2019,
making up 8.5 per cent of all
new cases that year. That is down
from 13 per cent four years earlier,
mainly due to higher-income
countries cleaning up their air.
“I think this is a good news
story for NO2. The fraction of
new paediatric asthma cases
that are attributable to NO2 has
dropped,” says Anenberg.
However, the team shows how
unevenly the burden today falls
on cities and poorer countries.
About two-thirds of the linked
asthma cases are in urban areas.
And while high-income nations
saw NO2-associated cases fall by
41 per cent – driven largely byNorth America – south Asia and
sub-Saharan Africa saw them rise.
The team used satellite and land-
use data to map annual average
NO2 levels globally, before taking
data on total childhood asthma
cases to estimate how many were
associated with NO2 (The Lancet
Planetary Health, doi.org/hb6v).
“It is important to note that
the actual pollutants in the trafficemission mix that cause asthma
remain elusive, and these results
do not suggest that we should
focus on only emissions of NO2
alone,” says Jonathan Grigg at
Queen Mary University of London.
Although figures on air
pollution and child asthma cases
are patchy in some parts of the
world, Anenberg says the results
stand and are a reminder that
governments need to translate
tough new guidelines from the
World Health Organization into
legal standards. “The key takeaway
for me is the vast majority of
people on the face of the planet
are breathing air pollution that
is unsafe,” she says. ❚
RAJ^ K^
RAJ/H
INDUSTANTI
MES/GET
TYAdam VaughanTHIS immaculately preserved
mygalomorph spider is one of the
many fossils that have emerged
from excavations at the McGraths
Flat, a 16-million-year-old fossil
site in New South Wales, Australia.
“It’s unlike anything that we
have seen alive today in Australia,”
says Matthew McCurry at the
Australian Museum Research
Institute in Sydney, a member
of the team that studied the
well-preserved spider fossil and
other McGraths Flat remains. With
a set of sturdy legs attached to its
4-centimetre-long body, “it’s an
extremely large spider”, he says.
Fossils at the site include
plants as well as vertebrates
and invertebrates, and they show
that the site was once a rainforest
(Science Advances, doi.org/hb96).
“Australia was becoming more
arid and most modern ecosystems
were developed,” says McCurry. “It’s
Australia’s origin story, in a way.” ❚
Palaeontology
Chen Ly
Australian fossil bonanza
Remains reveal what life was like in the country’s ancient rainforests
MI
CH
AE
L^ FRE
SENews