Ozone causes severe respiratory problems and thousands of cases of premature death each year by attacking the fatty lining of the lungs, according to new research. Scientists used neutrons to observe how even a relatively low dose of ozone attacks the lipid molecules that line the lung’s surface. These lipid molecules are crucial for the exchange of oxygen and carbon dioxide because they prevent the wet surfaces of the lung from collapsing.

Investigators created an artificial lipid monolayer to mimic the lung surface. This lipid layer was exposed to a dilute gaseous mixture of ozone, with changes in its structure or surface tension studied in real time. The concentration of ozone was around 100 parts per billion (0.1 ppm), equivalent to what air quality in a polluted city during summer.

The team showed that one of the lipid’s upwards-facing tails, known as the C9 portion, breaks off during the ozone degradation and is lost from the surface completely. The portion still attached to the lipid head then re-orientates itself and penetrates into the air?water interface.

The loss of the C9 portion causes an initial decrease in surface tension which temporarily increases surface area for gas exchange and efficient respiration. This effect is short-lived as the penetration of the rest of the molecule into the water results in a slow but pronounced rise in surface tension, producing an overall net increase.

We are not completely sure what causes the second stage of tension increase. The damaged lipid might be slowly dissolving in the water and leaving the interface entirely, or a slow reaction might be occurring that is damaging another part of the lipid not directly attacked by ozone,” said Katherine Thompson, Birkbeck, University of London.

“What we can say is that the slow increase in surface tension that occurs as a result of the ozone exposure would certainly damage the ability of our lungs to process oxygen and carbon dioxide, and could account for the respiratory problems associated with ozone poisoning.”