Heart attacks
from air pollution The number of heart attacks increases on
days with higher levels of pollution.
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COLLECTING DUST: Elgeseter
gate in Trondheim is close to St. Olavs/University Hospital,
and is one of the country’s most polluted streets. As the
levels of pollution increase, admittances to the hospital
also increase.
Photo: Gorm Kallestad/Scanpix
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Air pollution has first and foremost been
linked to allergies and asthma, but medical findings made by researchers
at St. Olavs Hospital/ University Hospital in Trondheim suggest
that air pollution may also contribute to heart attacks.
As early as 1992, the steel industry contacted
the Department of Occupational Medicine at the hospital with concerns
about the high number of steel workers who had heart attacks, says
Professor Bjørn Hilt.
“We began an epidemiological investigation,
and concluded that workers who were more exposed to fine steel dust
were also more at risk for heart attacks. At the same time, there
were results from other countries that also pointed in the same
direction.”
Since then, research has continued on the
subject, and results indicate that fine dust that irritates lungs
and airways also leads to an increase of certain substances in the
blood.
“When we inhale fine dust, the cells in our
airways release mediators, among them one that is called inter-leucin
6 (IL-6),which stimulates liver cells to increase the production
of fibrinogen. This in turn makes the blood coagulate more easily,
and this is where we believe the connection lies. If blood coagulates
more easily, this can lead to blood clots and heart attacks in some,”
says Hilt.
SUDDEN INCREASE
MORE DANGEROUS
The investigations conducted by researchers at St. Olavs
have shown that it might be the increase in pollution levels, rather
than the levels as such that may cause the infarction. High levels
over time do not seem to pose the same risk.
“We believe therefore, that the body adjusts
to pollution over time. Sudden increases in the level of pollution,
on the other hand, lead to a biological stress with increased production
of IL-6, and eventually more clotting,” Hilt explains.
“Tests that we conducted on tunnel workers
showed that the production of IL-6 and fibrinogen increased when
workers returned to work after having had some time off, but dropped
again after workers had spent a week in the polluted environment.”
Several years ago, this problem was investigated
by two medical students from the Department of Occupational Medicine,
which is affiliated with both the University Hospital and NTNU.
Together with the City of Trondheim’s Department of Environment,
they coupled a decade’s worth of statistics for people admitted
to St. Olavs with cardiac- and cardiovascular ailments with the
statistics for air pollution on one of Trondheim’s busiest roads.
“They found a connection,” Hilt says. “On
days with heavy air pollution, the hospital had more admittances
than on days with less pollution, by a statistically significant
amount.”
DIESEL WORSE
THAN DUST
The results indicate that the observed effects result from
exposure to nitrogen dioxide (NO2), which can be used as an indicator
of substances in diesel exhaust. Ordinary suspended dust does not
seem to cause the same results in relation to acute heart problems.
“We are not sure why this seems to be the case, but we believe that
the particles from diesel exhausts are so fine that they may trigger
much stronger cellular reactions in the airways. We also need more
research on this subject.”
COOPERATION WITH THE CITY
In the industrialised world, only cancer claims more lives than
cardiac- and cardiovascular disease. “That is why it is important
to know as much as possible about what causes cardiovascular diseases,
so that we can do a better job of preventing them.
By Christian Fossen
Contact: Bjørn Hilt, Department of Occupational
Medicine, Faculty of Medicine, NTNU.
Tel: +47 73 86 75 17, Email: bjorn.hilt@ntnu.no
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