Morning walkers and those who go for runs in winter should wear surgical masks to reduce the entry of pollutants in the airways and keep lung ailments like asthma and chronic obstructive pulmonary disease (COPD) at bay, a doctor has advised.

The same advice applies to those out cycling.

The World Health Organisation’s Global Disease Burden Study 2018 shows 30 per cent of all deaths from COPD are from India. The figure is “disproportionately high” when one takes into account the fact that India accounts for only 18 per cent of the world population.

Doctors urge people to take extra precaution against lung ailments during winter because of a phenomenon called “temperature inversion”. The phenomenon does not allow natural cleansing of pollutants from lower atmosphere, leading to an overload of particulates, the trigger for lung diseases, in the air.

In other seasons, the surface air is usually warmer than the air in the upper levels. As the hot air rich in pollutants rises, it is replaced by clean air from above, leading to natural cleansing of pollutants. In winter, the surface air, especially in the morning, is cooler that the air at higher altitudes.

“More air enters the airways when we walk briskly or run than when we are breathing normally. In winter, more air means more pollutants. Hence, the risk of COPD and asthma increases,” Raja Dhar, pulmonologist and director of Fortis Hospital, Anandapur, said on Tuesday.

The amount of pollutants entering the airways could be minimised if morning walkers, runners or cyclists wear surgical masks.

Dhar was speaking at a programme in the hospital to mark World COPD Day, which falls on Wednesday.

Pollutants in the lungs could lead to asthma, which is narrowing of the airways, a condition that is reversible. Another possibility is COPD, which, too, is gradual shrinkage of the airways. COPD, however, is non-reversible.

The telltale signs of COPD one should look out for are dry cough that does not respond to “normal” medicines like cough syrup, breathlessness on exertion, recurrent respiratory infections and noisy breathing.