According to researchers, taking antioxidant supplements could help reduce the effects of ozone pollution on lung health and help the body prevent damage from toxins and pollutants.
US researchers from the University of North Carolina and from the National Institutes of Health in Maryland gave supplements to half of a group of people whose diets were altered so they were not eating foods rich in antioxidants.
When exposed to ozone, those who had taken the supplements had better lung function, and were had much higher levels of vitamins than those who had not.
According to the scientists, it shows that people whose lungs have been damaged by ozone could be given supplements to improve their condition.
The research is published in the American Journal of Respiratory and Critical Care Medicine, the journal of the American Thoracic Society.
Ozone gas is produced in photochemical smog produced by chemical reaction under ultraviolet (UV) light from the sun. Other studies have shown that the gas does damage the lung, and causes decreased lung function.
Thirty-two healthy, non-smoking adults aged 18 to 35 were put on an antioxidant-restricted diet for three weeks.
Antioxidants include vitamin E, found in vegetable oils, vitamin C from fruit, and beta-carotene in yellow, orange and dark green vegetables like pumpkin, carrots and spinach.
After a week during which they had been exposed to air that had been filtered and purified, they underwent several tests on how their lungs functioned.
For the next two weeks, half the group in the study were given antioxidant supplements, and the other half a placebo. All were exposed to 0.4 parts per million of ozone gas for two hours, while intermittently taking moderate exercise. Researchers then gave them a lung "wash out", or brochoalveolar lavage.
This showed that those who had been given supplements had 85 per cent higher levels of vitamin C, 28 per cent more vitamin E and 27 per cent more vitamin A, compared to the group which received the placebo.
They also showed a 24 per cent improvement in one lung test and a 30 per cent increase in another, compared to the group who did not take the supplements.
However there was no difference between the groups in a test for inflammatory response.