Patna: In 2023, aerosol pollution in the state of Bihar has been anticipated to grow the highest as compared to other states in the country. The forecast, according to a latest study, shows that aerosol pollution will continue to remain in the “highly vulnerable” red zone, raising alarm bells for the health of residents across major cities in Bihar.
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 present 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.
Falling in the Indo-Gangetic plain, Bihar currently falls under the ‘red category’, which is the highly vulnerable zone with AOD ranging between 0.6 to 0.75. Aerosol pollution is expected to rise by 8% further pushing the AOD over 0.8 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, who is principal author of this study and associate professor of environmental sciences at Bose Institute said, “Bihar has the highest mean and trend in the past for aerosol pollution in India. The government should be more careful about indoor pollution and encourage liquified petroleum gas (LPG) subsidies. Along with this, surveillance and awareness about air pollution and its harmful effect is essential across the state.”
Among major aerosol pollution sources for Bihar, vehicular emissions, solid fuel burning and construction dust are the three major sources of pollution in the city. “Solid fuel burning is the most prominent source of aerosol pollution throughout the years 2005-2019 according to our study. During this time, vehicular emission contribution remained almost unchanged (18-19%) while construction dust showed enhancement from 2005-2019 increasing from 12% to 15% in Bihar,” said Monami Dutta, first-author of the study and senior research fellow, Bose Institute, Kolkata.
The study highlighted a list of recommendations to curb rising aerosol pollution for Bihar. Chatterjee explained as observed from the study that solid fuel burning was a dominant aerosol pollution source in the state due to the increase in the price of LPG that prompted underprivileged people to shift back to wood or other polluting fuels. “LPG subsidies need to be encouraged especially for underprivileged people,” he said.
Dutta added that vehicular emissions had remained the second dominating source of air pollution in the state. “Such dominance can only be avoided by the proper implementation of up-gradation of engines, banning 15-year-old vehicles etc.,” she said.
Division of categories for AOD (Based on percentiles, there are 4 colour zones)
Green (Safe Zone)- AOD value less than 0.3
Blue (Less Vulnerable Zone)- AOD value between 0.3–0.4
Orange (Vulnerable zone)- AOD value between 0.4–0.5
Red (Highly Vulnerable zone)- AOD value greater than 0.5
In the paper, the threshold for aerosol pollution (AOD) vulnerability has been considered as a value of 0.4, and the states above this threshold are considered vulnerable.