The number of heart attacks increases on days with higher levels of pollution.
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