“Luckily, most of the particles do not remain in the underground for any length of time,” says scientist Dr. Hanna Karlsson. “However, particle levels are often very high. My results show that there is every reason to speed up the work being done to clean the air in the underground.”

Every year, some 5,300 Swedes die premature deaths from inhaling the microscopic particles of coal, asphalt, iron and other materials that pollute the city’s air. These particles, which are the result of incomplete combustion, road surface attrition, etc. could be reduced if the right steps were taken; the problem is that it is not known which particle sources pose the greatest threat to human health.

To build up a picture of which particles are the most harmful, Karlsson has compared how particles from a variety of sources affect cultured lung cells. The results, which are presented in her thesis show that particles from the Stockholm underground are much more damaging to cellular DNA than the other sources tested e.g. wood smoke and cars.

The airborne particles in the underground system largely comprise iron, and are formed by the abrasion of the train wheels against the rails. The damage is caused when these particles enter the body and form free radicals in the body’s cells. Free radicals are highly reactive molecules that can prove harmful to the cell’s DNA; although such damage can often be repaired by the cell, it can sometime remain untreated, and this increases the risk of cancer.

MEDICA.de; Source: Karolinska Institutet