6 | New Scientist | 24 August 2019Pollution Organ transplantsRuby Prosser Scully Clare WilsonFIFTEEN studies about transplanted
organs by researchers in China have
been retracted due to concerns the
work may have used organs from
executed prisoners, according to
the website Retraction Watch,
which monitors questions raised
over published research.
China’s government said in 2015
that the nation had stopped using
organs from executed prisoners,
which is illegal under international
conventions. But campaign groups
and some doctors suspect the
practice continues, particularly
involving prisoners of conscience.
Some claim that targeted groups
include Uighurs, a Muslim ethnic
minority in China, and practitioners
of Falun Gong, a belief system
similar to Buddhism that has
been outlawed.
Various journals that publish
research into organ transplants
have previously said that, for ethical
reasons, they won’t publish any
work that used prisoners’ organs.
Yet earlier this year, campaigners
highlighted 400 published papers
that they suspect may have
involved organs taken from
prisoners (BMJ Open, doi.org/c2ks).
Many came from work done
before 2010, when China didn’t
have the systems in place to get
donor organs from people who are
brain dead, as happens in other
countries. Now some of the journals
involved seem to be taking action.
The journal Transplantation has
retracted seven papers, saying in
an editorial that “it is clear, with
the benefit of hindsight... that
most deceased donors were
from executed people”.
Jacob Lavee, an Israeli heart
surgeon who is a member of
campaign group Doctors Against
Forced Organ Harvesting, welcomes
the news but says politicians also
need to act. “Chinese transplant
physicians are committing a crime
against humanity,” he says. ❚Suspicious organ
studies retracted
by journalsWALLS blanketed in moss are
popping up in major cities,
along with promises that they
can help reduce air pollution –
but can a few square metres
of plant matter really tackle
the smog?
Berlin-based Green City
Solutions believes so. Its moss
walls, called CityTrees, are about
4 square metres in size. It says
they can filter up to 80 per cent
of pollution particles out of
the air, including the tiny
ones linked to respiratory
and cardiovascular diseases.
The walls collect rainwater,
which is pumped through an
irrigation system to the plants,
powered by solar panels. These
also drive fans to increase
airflow through the plants. As a
result, the firm says its product
filters 3500 cubic metres of air
an hour, which is equivalent to
the total volume of air breathed
by 7000 people in that time.
Around 50 CityTrees havebeen installed in European cities
in bus stops and busy streets
where people are exposed to
harmful particles emitted from
passing traffic – one of the
biggest sources of air pollution.
The European Commission is
interested in the idea and is
funding a dozen moss walls in
Berlin over the next year. Each
CityTree costs about $60,000.
Alison Haynes at the
University of Wollongong in
Australia and her colleagues
recently looked at how
effectively moss and trees
absorb pollution. They found
that moss was up to four times
better at trapping particles
than the native Australian tree,
Pittosporum undulatum.
“Mosses are like a ragged
carpet, so there are lots of little
spots where little particles
can get caught and trapped,”
says Haynes. Because moss
lacks roots, it gets minerals
through its leaves, absorbing
them from the air. As it does
so, it also traps particles of
pollution, such as heavy
metals, in its tissue.But this doesn’t mean moss
walls will necessarily protect
people from pollution at busy
bus stops, says Zoran Ristovski
at the Queensland University of
Technology in Australia. In a
small room, a moss wall only
needs to filter a fraction of
new air each hour, but tens or
hundreds of times this volume
of air is pushed past by buses,
he says. Consequently, a moss
wall in a street is unlikely to
make any difference, he says.This view is supported
by a study of CityTrees by
researchers at the Netherlands
Organisation for Applied
Scientific Research. They found
that eight walls installed in a
busy street in Amsterdam failed
to reduce the concentration of
particulate matter and nitrogen
dioxide. Their report concluded
that even doubling the number
of moss walls would do little to
improve their effectiveness.
Different solutions will be
needed depending on an area’s
layout, says Ruby Michael at
Griffith University in Australia.
Where streets are flanked by
tall buildings to create urban
canyons, she says, tree planting
can backfire because trees can
reduce airflow – and so moss
walls may be a better option.
Cities are unlikely to rush
to replace their trees just yet.
“It’s important to remember
that street trees provide a
whole host of other benefits,
including refuge and habitat
for urban wildlife, shade and
cooling for people on the
street, and reduction of urban
heat islands,” says Michael. ❚Moss-covered walls
installed to clean city air
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News
A moss-cloaked
CityTree being fitted
in a Berlin street80%
Moss walls are said to remove this
proportion of pollution particles