Chandigarh,  Aerosol pollution in Punjab is anticipated to rise by 20 per cent in 2023, and continue to remain in the "highly vulnerable" red zone for aerosol pollution, says a study.

High aerosol amounts include particulate matter (PM2.5 and PM10) among other pollutants as well as sea salt, dust, black and organic carbon. If inhaled they can be harmful to people's health.

Aerosol optical depth (AOD) is the quantitative estimate of the aerosol present in the atmosphere and it can be used as a proxy measurement of PM2.5.

The study -- A deep insight into state-level aerosol pollution in India -- by researchers Abhijit Chatterjee Associate Professor and his PhD scholar Monami Dutta from Bose Institute, Kolkata, provides a national scenario of aerosol pollution with the long-term (2005-2019) trend, source apportionment, and future scenario (2023) for various Indian states.

Punjab currently falls under the red category which is the highly vulnerable zone with AOD over 0.5. Aerosol pollution is expected to rise by 20 per cent further pushing the AOD higher within the vulnerable (red) zone in 2023.

The values of AOD range from 0 and 1. 0 indicates a crystal-clear sky with maximum visibility whereas a value of 1 indicates very hazy conditions. AOD values less than 0.3 fall under the green zone (safe), 0.3-0.4 is blue zone (less vulnerable), 0.4-0.5 is orange (vulnerable) while over 0.5 is the red zone (highly vulnerable).

Chatterjee, Principal author of the study, said, "In the past, all states in the Indo Gangetic Plain (IGP) were already in the highly vulnerable zone in the context of air pollution. Among all states in the IGP, the highest increase in AOD is projected for Punjab (approximately 20 per cent rise in AOD with respect to 2019). Since in the last phase it was observed that crop residue burning is the major source of air pollution, restriction of this is highly recommended."

Among major aerosol pollution sources for Punjab from 2005 to 2009, the study found that vehicular emissions were the highest followed by solid fuel burning and thermal power plant emissions.

However, between 2010 and 2014, crop residue burning became the second biggest source of aerosol pollution. In the follow up years from 2015 and 2019, crop residue burning became the biggest source contribution to aerosol pollution around (34-35 per cent) emissions followed by thermal power plants (20-25 per cent) and vehicular emissions (17-18 per cent).

"The emissions from thermal power plants also increased massively from 12 to 15 per cent in Phase-1 to 20a"25 per cent from 2015-2019. The positive side of this narrative is that vehicular emissions (30-32 per cent in 2005-2009 to 17-18 per cent in 2015-2019) and solid fuel burning both decreased over the years," said Monami Dutta, first-author of the study and Senior Research Fellow, Bose Institute, Kolkata.

The research study further analysed that Punjab has observed one of the highest mean Aerosol Optical Depth (AOD) levels in India (falling between 0.65 and 0.70).

"However, the trend of rise in AOD was lower in the years from 2013-2019 (0.005) as compared to 2005-2012 (0.012). It might have been a result of the stringent policy implementation focused especially on the IGP region during this period but the rise has been significant due to the increase in crop residue burning," explained Chatterjee, adding since there was no quantitative data for cross residue burning from the state or central government, the exact decrease was not quantified in this study.

The study highlighted a list of recommendations to curb rising aerosol pollution for Punjab.

Immediate restriction in the installation of new thermal power plants and more focus given on adoption of renewable energy sources as well as alternative energy sources like hydropower should be encouraged in Punjab, the study said.