New Delhi, Sept. 1: Indians have the poorest lungs among 17 populations across four continents, according to new research that has stirred speculation that the health effects of air pollution in India may be worse than hitherto suspected.
An international study that investigated the lung functions of healthy, non-smoking adults from 17 countries has found that the efficiency of breathing of South Asians, mainly Indians, is 30 per cent lower than that of Europeans and North Americans.
This difference in lung function is much larger than previous estimates from earlier studies that compared South Asian Indians to Caucasians and cannot be explained by differences in weight, height, and urban or rural living.
Poor air quality could explain this — many years of breathing polluted air could impair lung functions, said Kiruba Shankar, an epidemiologist at the St Johns Medical College, Bangalore, and a member of the study team.
The study did not look into exposure to air pollutants. So the effects of maternal and child nutrition, which can also influence lung health, cannot be ruled out yet, Shankar told The Telegraph.
The study, co-ordinated by Salim Yusuf, an India-educated professor of medicine at McMaster University in Canada, examined lung functions of 46,000 women and 17,000 men. Its results were presented at the American Thoracic Society meeting this year.
Some researchers believe that the poor lung functions observed in Indians serve as a grim reminder of Indias colossal task of cleaning the air that hangs outdoors over most Indian cities and indoors at rural and urban homes.
I was shocked to see a 30 per cent difference — this should be an eye-opener for us, said Sundeep Salvi, a pulmonologist and director of the Chest Research Foundation in Pune, who is independently studying lung functions in rural and urban areas.
Scientists applied sophisticated statistical techniques to correct for the effects of age, height and gender — all of which can influence lung functions — to estimate the true differences in lung functions. Earlier studies had suggested that lung functions of Indians were about 10 per cent to 15 per cent lower than those of Caucasians.
Differences in genetic as well as vastly different environmental factors may be contributing to the large differences we see in lung function, Mylinh Duong, an assistant professor of medicine at McMaster University, told this newspaper.
Anecdotal evidence indicates a steep rise in the number of patients with airways disease, including asthma and chronic obstructive pulmonary disease (COPD) in Indian cities, doctors said yesterday at a conference on air pollution organised by the Centre for Science and Environment, New Delhi. I think the incidence of respiratory illness has gone up 10 times over the past 20 years, said Sanjeev Bagai, a consultant paediatrician.
The gains some of our cities have made by switching to compressed natural gas and introducing vehicular emission standards are being eroded by the rising number of vehicles, said Anumita Roychowdhury, deputy director of the CSE.
The lung function tests examine the efficiency through which a person can breathe. Long-term inflammation caused by prolonged exposure to gaseous pollutants or tiny particles can impair lung functions.
A 15-city study in India published two years ago has established a strong association between the density of diesel trucks in the neighbourhood and asthma, said Salvi, who estimates about 5 per cent of school-going children in India are diagnosed with asthma.
And while COPD is primarily linked to smoking, we also encounter patients with COPD who have never smoked in their lives, said Salvi. India has a huge inventory of potential lung irritants that we routinely encounter in the city air or inside our homes — traffic and industry emissions, biomass and wood burning, incense sticks, and Diwali crackers.