Study finds little difference in air pollution levels between urban and rural India

As urban India battles post-Diwali air pollution, a new Indo-US study has shown that rural India is no better when it comes to inhaling toxic air.

When scientists from Indian Institute of Technology, Bombay and Colorado State University calculated the amount of PM 2.5 (dust particles of 2.5 micron size) across India from satellite measurements, they did not find much difference in air pollution levels between urban and rural areas in different parts of the country.

"We wished to definitively evaluate non-urban versus urban impacts of air pollution through the use of all-India data at high spatial resolution (about 4.5 km) for a whole year,” said Chandra Venkataraman, a professor at IIT Bombay and one of the researchers involved in the study.

Armed with satellite data, the scientists looked at the PM 2.5 level in six regions across India and found that the Indo-Gangetic plain was the most polluted one with the PM 2.5 level of 100 microgram per cubic meters throughout the year while in the non-urban areas of the same zone, the contaminant level was in excess of 90 microgram.

In the remaining five zones, the level of lethal dust varies between 55-90 micrograms but there is barely any difference between urban and non-urban areas in eastern and southern India. In southern India, PM-2.5 concentrations in non-urban locations are in the range of 30–50 microgram as against the urban average of 50 microgram.

“There is little difference between urban and non-urban regions and the annual mean PM 2.5 levels are much larger than India’s national ambient air quality standard of 40 micrograms in all of the six regions,” the scientists reported in a recent issue of the Proceedings of the National Academy of Sciences.

The researchers also estimated that air pollution killed an excess of 10.5 lakh people early in their lives owing to heart and lung diseases every year. Out of this, 69% of the deaths are in non-urban areas. This means more than 7 lakh people experience early death annually due to air pollution in rural areas.

While the sources of air pollution vary, with almost similarly elevated levels of PM 2.5 levels in urban and rural regions, both groups of the population face comparable health risks.

Since air pollution is typically considered an urban problem, rural India with 70% of India's population generally escapes attention.

As per the study, residential cooking in chulhas (clay ovens) with biomass fuels (wood, crop residue and dung cakes) is the single largest source impacting outdoor air pollution in India, though it does not get the same attention as vehicular and industrial pollution as well as stubble burning.

“The biggest challenge in estimating air quality from the ground is the lack of sufficient monitoring stations,” said A R Ravishankara, a team member from the IIT and lead author of the study. Non-urban India, which faces a high risk of health problems and death, hardly has any monitoring setups, which is needed to inform and steer policy decisions. “This is one area where India could significantly enhance its capability,” he added.

The new research comes two years after another group of US scientists had shown that the death rate due to air pollution was nearly identical in rural and urban India.