A simple blood test may soon reveal the damage caused to lungs by the atmospheric pollutant ozone.
Traffic fumes can generate ozone
It is based on detecting levels of a protein, CC16, secreted by cells in the walls of tiny respiratory vessels called bronchioles.
Experiments have shown protein levels are higher- and lung damage higher - in people exposed to ozone.
The work, by University Hospital, Umeň, Sweden, is published in the European Respiratory Journal.
Previously the only way to assess lung damage caused by exposure to ozone was to take a tissue sample.
Not only was this more invasive, it appears not to be as sensitive as the new test.
Ozone at very high altitudes provides an essential protective shield against the sun's dangerous ultraviolet rays.
However, it is also produced closer to ground level when sunlight reacts with pollutants spewed out by vehicle exhausts.
Breathed in it can aggravate chronic respiratory conditions, and it has been shown that during periods of particularly high ozone levels deaths and hospital admissions from respiratory disease increase.
Laboratory tests have also shown that ozone can led to inflammation of the lungs, and injury to the fine layer of epithelial cells that coat the airway surface.
These cells secrete CC16 as a way to try to minimise inflammation.
The new test is based on the theory that this protein leaks into the blood when the epithelial cells are damaged and thus form less of a protective barrier than usual.
Therefore, the more protein found in the blood, the greater the damage that has occurred.
The researchers monitored 22 healthy adults, who breathed in pure air, or air enriched with ozone during an exercise session.
Blood samples showed that CC16 concentrations in the blood were significantly higher after breathing the ozone mixture.
Conversely, CC16 levels were lower than normal after the volunteers breathed in air completely free from ozone.
The researchers hope that a test can be developed in the near future, but they warn that CC16 levels do vary from one individual to another, and even in the same individual at different times of day.
Lead researcher Dr Anders Blomberg said: "Clearly, this element will need to be taken into account when the biomarker is used to assess the impact of atmospheric pollution.
"There is still plenty of work to be done, but we are making progress.
"We should soon complete work on developing a specific mathematical model designed to take daily CC16 variations into account."
Professor Malcolm Green, of the British Lung Foundation, told BBC News Online: "At present this is a research tool, and it appears that there are many influences on the level of this blood marker so that it is not possible to draw any conclusions from tests in particular individuals.
"However, this is exciting and novel research which may well lead to a much deeper understanding of the effect of ozone on the lungs of people exposed to environmental pollution."