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Sharmistha Chakraborty1
, Maromi Roy1, Nazima Sultana2and Mehdi Al Kausor1*
1Department of Chemistry, Science College, Kokrajhar, Assam, India.
2Department of Chemistry, University of Science and Technology, Meghalaya, Shillong, India
Corresponding Author E-mail: mehdialkausar@gmail.com
Article Publishing History
Article Received on : 11 Nov 2024
Article Accepted on : 23 Jan 2025
Article Published : 30 Jan 2025
The daily air pollution levels are crucial, especially for those people who are suffering from some air borne diseases. The air quality index (AQI) values may increase due to increased emissions from vehicles, construction activities, flyovers, road widening, traffic discharge, and lack of rain. Monitoring these factors is essential for maintaining a healthy environment. The study was conducted w.r.t. some major gaseous air pollutants like CO, SO2, NO2, O3, and NH3 along with some fine particulate matter such as PM10 and PM2.5 covered under AQI worldwide. This paper analyzes the AQI data in Guwahati City, Assam, India, aiming to raise public awareness about potential health issues and suggest effective measures for controlling the deteriorating air quality and promoting swift action against air pollution. The investigation revealed a slight increase in aggregate levels of five pollutants, resulting in poor overall AQI levels during the winter session. The study suggests that the increase in AQI value in Guwahati, Assam, India, may be due to construction, flyovers, road widening, and excessive traffic, leading to low visibility and suggests government intervention through smart policies and regular monitoring. The study could be expanded to other districts and regions, conducted cross-nationally for more tangible results, and seasonal variations may be increased for better results.
KEYWORDS:Air Quality Index; air pollution; NO2; Particulate Matter 10; Particulate Matter 2.5; SO2
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Copy the following to cite this article:Chakraborty S, Roy M, Sultana N, Kausor M. A. Analysis of Trends in Air Ambient Quality Index: A Case Study of Guwahati City of Assam, India. Orient J Chem 2025;41(1).
Chakraborty S, Roy M, Sultana N, Kausor M. A. Analysis of Trends in Air Ambient Quality Index: A Case Study of Guwahati City of Assam, India. Orient J Chem 2025;41(1). Available from: https://bit.ly/40wgap8
Introduction
The global pollution in air has been appeared as a rising problem across the globe in many metropolitan cities. In recent years, India is seeming industrial, rapid urbanization, infrastructure and economic growth1 and the issue of pollution in air in metropolitan cities is a serious concern2. The air pollution is occurred mainly due the presence of gases like CO, SO2, NO2, O3, and NH3 along with some particulate matter such as PM10 and PM2.5. PM10 (diameter = 10 μm) and PM2.5 (diameter = 2.5 μm) are both found in dust and smoke. The PM 10 particles can easily penetrate nose, throat, and lungs and cause coughs, colds and eye burns. Similarly, due to higher levels of PM2.5, the atmosphere appears opaque and visibility is reduced. Many Indian metropolitan cities are considered to be the among most 20 polluted cities across the globe. In 2015, almost 10 lakhs of people perished in India only as a result of particulate matter pollution3. The particulate matters are regarded as the most dominant pollutant which are contaminating the air by automobiles, industrial, house-hold activities across many parts in India4. Severe air pollution increases the risk of heart stroke, heart related diseases, other acute respiratory diseases including cancer in lungs and asthma. Higher concentration of SO2 and NO2 in the atmosphere may exert serious effect on soil, water, and cropping pattern5,6. In addition to that, air pollution also reduces the atmospheric visibility and change the climate7. Even the internal quality of air also remarkably impacts the human health and overall well-being of those who reside in these spaces8,9.
The quality of air on day-to-day basis is measured in terms of the AQI value. AQI is used to estimate how polluted the air is and how that local air quality may affect a person’s health. AQI is obtained from the average readings of some air quality sensors. This AQI may increase as result of any kind of activities that leads to air pollution. The pollutants detected by the sensors include gaseous pollutant viz. CO, O3, NO2, SO2 etc. along with PM10 and PM2.5. The increasing levels of these gases and particulate matters are considered to be severe air pollutants in urban areas10,11. The AQI sometimes may increase when the air gets polluted to a significant extent. The main reasons behind this are the ongoing construction of houses, buildings and multi-story apartments, flyovers, road and highway widening activities12 polluted gas emissions from excess vehicles and also the atmosphere with dust, sand and smog due to lack of rainfall. This causes poor visibility and burns people’s eyes.
In India, the AQI provides a straightforward, 1-number-1-color-1-description for individuals to assess the air quality in their specific area which was launched by National Air Quality Index (NAQI) mission. The Central and State Pollution Control Boards (CPCB & SPCB) regularly conduct a National Air Monitoring Program (NAMP) that covers as much as two hundred forty cities across the country. For continuous monitoring of the real time data, authorized centers were established in several cities. A board of members comprising air quality experts from medical colleges and hospitals, education departments, advocacy groups and state pollution control boards was formed along with Indian Institute of Technology (IIT) Kanpur. The I.I.T. Kanpur along with the board members suggested the AQI scheme13. The AQI has six categories, such as good, satisfactory, moderately polluted, poor, very poor, and severe. The]is proposed AQI covers eight pollutants viz CO, SO2, NO2, O3, NH3 Pb, PM10, and PM2.5 for which short-term national air standards (average terms per hour) are set. Based on levels of these atmospheric pollutants and the associated standards, the potential health impacts are suggested for each of these pollutants for a particular range of AQI values. According to the initial inputs, the range of various AQI categories and the various pollutants and the potential health impacts for these pollutants are given in Table-1 and Table-2 respectively13.
Table 1: The six categories of AQI range along with various pollutants.
AQI Range PM10(μg/m3)
24 h
PM2.5(μg/m3)
24 h
NO2(μg/m3)
24 h
O3(μg/m3)
8 h
CO(μg/m3)
8 h
SO2(μg/m3)
24 h
NH3(μg/m3)
24 h
Pb(μg/m3)
24 h
Indicating Colour 0-50 0-50 0-30 0-40 0-50 0-1.0 0-40 0-200 0-0.5 Light Blue 51-100 51-100 31-60 41-80 51-100 1.1-2.0 41-80 201-400 0.5-1.0 Green 101-200 101-250 61-90 81-180 101-168 2.1-10 81-380 401-800 1.1-2.0 Pink 201-300 251-350 91-120 181-280 169-208 10-17 381-800 801-1200 2.1-3.0 Yellow 301-400 351-430 121-250 281-400 209-784* 17-34 801-1600 1200-1800 3.1-3.5 Red 401-500 430+ 250+ 400+ 784+ 34+ 1600+ 1800+ 3.5+ MaroonTable 2: The six categories of AQI and the associated health effects of each category
AQI Category Associated health effects 0-50 Good Lowest impact 51-100 Satisfactory Sensitive people may have slight difficulty breathing. 101-200 Moderately polluted Asthma, lungs and heart disease, children and orderly people with may suffer breathing. 201-300 Poor Long time exposure may cause breathing difficulty, and heart disease. 301-400 Very poor Long time exposure can develop respiratory diseases. Such affects may be prominent for people suffering from lung and heart disease. 401-500 Severe Long time exposure may develop respiratory diseases even in healthy people as well, and may cause severe health issues in people suffering from lung and heart disease.Source: Central Pollution Control Board, Ministry of Environment, Forests and Climate Change
The monitoring of the AQI of a particular region is crucial for swift action against the deterioration of quality of air and creating a public awareness. However, the critical analysis and research on this field is limited. In this paper, comprehensive analysis of the ambient AQI data in terms of, CO, SO2, NO2, NH3, O3, PM10 and PM2.5 of Guwahati City of Assam, India is carried out to create an awareness about the AQI among the mass people regarding the probable health issues that might arise due to air pollution and suggest some effective measures in controlling the air quality index.
Materials and Methods
In India, the ambient air quality data is collected by monitoring the continuous ambient air quality at the authorized monitoring stations. The monitoring of air pollutants is being conducted with the assistance of State Pollution Control Boards (SPCB), Pollution Control Committees (PCC). The CPCB collaborates with these agencies to ensure the uniformity and consistency of air quality data. At the AQI monitoring sites, all data for specific pollutants are taken from its 24-hour average concentration (8-hours in the case of CO and O3). Sometimes data for the pollutants may not be monitored at the stations. The AQI is calculated based on data for the lowest three pollutants, including PM2.5 or PM10, which requires a minimum of 16 hours of data. It is determined in real time by an automated web-based system without any human intervention, displaying the average, minimum and maximum levels of the selected pollutants along with the average AQI values.
The data required for the present investigation were collected from the website of CPCB (https://airquality.cpcb.gov.in/AQI_India_Iframe/) under Ministry of Environment, Forest and Climate Change (MoEFCC), Govt. of India. The monthly variation of the average AQI values is then critically analyzed and the ambient air quality at each sampling sites are categorized from which information regarding the status of the air quality is ascertained.
Study Area
Guwahati City, located in Kamrup district of Assam, India, is the largest commercial, industrial, and educational center in the N-E region. The location of the city is in between 25.46o and 26.49 o North Latitude and between 90.48 o and 91.50o East Longitude. The Guwahati Metropolitan area have a population of around a million and a population density of 2695.43/km2.
The city is located on an undulating plain with altitudes ranging from 49.5 to 55.5 meters above sea level, surrounded by hillocks, swamps, marshes, and water bodies like Deepor Beel, Silpukhuri, Dighali Pukhuri, Borsola Beel and Silsakoo Beel. The southern and eastern sides of the city are sorrounded by hillocks. The central part of the city also has small hillocks like Sarania hill (193 m), Nabagraha hill (193 m) and Chunsali hill (293 m). The sampling was done at four different locations which are IIT Guwahati (Location: S-1), LGBI Airport (Location S-2), Pan Bazar (Location S-3), and Railway Colony (Location S-4). The ambient air quality data in these four stations were collected from the CPCB website.
Results and Discussion
The maximum AQI at S-1 for the month of October/2022 was reported as 148 on dated 20/10/2022 with PM2.5 particles being the prominent one. Similarly, the maximum AQI values of the other three sampling stations were reported as follows: 96 on dated 01/10/2022 at S-3, and increased to 188 on dated 26/10/2022 at S-4 with prominent particles being PM10 and PM2.5 respectively. Average AQI at S-2 was not recorded during this month and the overall AQI was found to be moderately polluted as S-1 and S-4 but satisfactory at S-3. In the month of November almost similar data was recorded: 175 on dated 23/11/2022 at S-1, 170 on dated 23/11/2022 at S-3 and 158 on the same date at S-4 with prominent particles being PM2.5 in all sampling sites. On this month also, the AQI at S-2 was not recorded. The overall AQI was found to be moderately polluted. In the month of December/2022, the maximum AQI at S-1 was reported as 305 on dated 27/12/2022 with PM2.5 particles being prominent. Similarly, the maximum AQI values of the other three sampling stations were reported as follows: 279 on dated 27/12/2022 at S-2, 282 on dated 31/12/2022 at S-3 and 312 on dated 31/12/2022 at S-4 with prominent particles being PM2.5 at S-1, S-2 and S-4 and PM10 at S-3. The overall AQI was found to be poor at S-1, S-2 and S-3, but very poor at S-4.
Table 3: Analysis of maximum AQI and the level of pollution.
Months Sampling site Maximum AQI Date Category October/2022 S-1 148 20/10/2022 Moderately polluted S-2 NA NA – S-3 96 01/10/2022 Satisfactory S-4 188 26/10/2022 Moderately polluted November/2022 S-1 175 23/11/2022 Moderately polluted S-2 NA NA – S-3 170 23/10/2022 Moderately polluted S-4 158 23/10/2022 Moderately polluted December/2022 S-1 305 27/12/2022 Poor S-2 279 27/12/2022 Poor S-3 282 31/12/2022 Poor S-4 312 31/12/2022 Very poorJanuary/2023
S-1 359 16/01/2023 Very poor S-2 346 15/01/2023 Very poor S-3 386 15/01/2023 Very poor S-4 419 15/01/2023 SevereFebruary/2023
S-1 346 06/02/2023 Very poor S-2 348 21/02/2023 Very poor S-3 355 21/02/2023 Very poor S-4 356 21/02/2023 Very poorMarch/2023
S-1 333 10/03/2023 Very poor S-2 258 12/03/2023 Poor S-3 289 12/03/2023 Poor S-4 296 12/03/2023 Poor* NA: Not Available
Similarly, in the month of January/2023 almost similar data was recorded: 359 on dated 16/01/2023 at S-1, 346 on dated 15/01/2023 at S-2, 386 on dated 15/01/2023 at S-3 but the average AQI was increased to 419 on dated 15/01/2023 at S-4 with prominent particles being PM2.5 and PM10 respectively. However, unfortunately in this month, the overall AQI was found to be very poor except at S-4 where, the overall AQI was found to be severe. Again, in the month of February/2023 almost similar data was recorded: 346 on dated 06/02/2023 at S-1, 348 on dated 21/02/2023 at S-2, 355 on dated 21/02/2023 at S-3, and 356 on dated 21/02/2023 at S-4 with prominent particles being PM2.5 in all the sampling sites. However, unfortunately in this month, the overall AQI was also found to be very poor. It was found that the PM10 levels during were higher than usual, indicating longer residence times due to stagnant conditions and low mixing heights in the atmosphere14.
On February 21, the National AQI bulletin of the CPCB revealed that at 7 pm, at the railway colony monitoring station (S-4), the PM2.5 and PM10 levels had come down to unhealthy levels. The Superintendent of Gauhati Medical College and Hospital, Assam reported that 36 children with bronchiolitis, asthma and pneumonia problems under the influence of unhealthy air were admitted to the Hospital. However, their health gets better later on. The CPCB’s national AQI bulletin showed that on 19th February, 2023 at around 10 pm, the PM2.5 and PM10 around the railway colony monitoring station had deteriorated to two “severe” levels. Even as compared to around 6 a.m. the next day, the level of PM2.5 rose and touched a high value of 353 at around 10 am. According to data from the AQI bulletin on 21st February, at around 7 pm, the PM2.5 and PM10 levels have deteriorated to two “unhealthy” levels. On the other hand, in the month of March/2023 the average AQI was recorded as follows: 333 on dated 10/03/2023 at S-1, 258 on dated 12/03/2023 at S-2, 289 on dated 12/03/2023 at S-3 but the average AQI was slightly decreased to 296 on dated 12/03/2023 at S-4 with prominent particles being PM2.5 at S-1 and S-2, but PM10 at S-3 and S-4 respectively. However, in this month, the overall AQI was found to be very poor at S-1 and poor at other sampling stations.
Policy Implication and Suggestions
As the value of AQI increases, public health risks may increase. Especially children, elderly people and people suffering from respiratory or cardiovascular diseases may be affected. During this time people should generally be avoided to reduce outdoor physical activities or even avoid going out from homes. Masks or masks should be used if you have to go out for special purposes. Although the AQI level in Guwahati city has gone down recently but if we are satisfied, it will not happen. The way climate is changing now, no one can predict when the situation is again. Therefore, it is time for the CPCB, SPCB, the Government and all concerned authorities to prepare a long-term plan and think about how to keep the air quality of the city good and take appropriate action. It is important to note that we all should be aware of the daily levels of air pollution. Especially those suffering from diseases caused by exposure to polluted air need to be careful by monitoring the quality of AQI. The AQI value may increase due to increased emissions of various types of polluting gases in the atmosphere. For example, excessive vehicular movement during peak hours and industrial activities as well as daily construction activities may result in an increase in air pollutants15,16. Air pollution can occur in local areas due to stable air, often cyclones, temperature reversals, or low wind speeds, thereby obscuring the atmosphere around due to chemical reactions between high concentration pollutants and air pollutants.
The authors believe that main reason behind this increase in AQI value at Guwahati city of Assam, India may be due to the ongoing construction of houses, buildings and multi-storied apartments, flyovers, widening of roads and highways, discharge of polluted gas from excess traffic as well as lack of rain engulfing the atmosphere with dust sand, smoke and fog (smog), which resulted in low visibility of people. The study recommends the government adopting forced measures to combat pollution in cities, including smart policies, legislation, and regular monitoring of AQI values, with the aim of ensuring a pollution-free environment.
Conclusion
It is important to note that we all should be aware of the daily levels of air pollution. Especially those suffering from diseases caused by exposure to polluted air need to be careful by monitoring the quality of AQI. The AQI value may increase due to increased emissions of various types of polluting gases in the atmosphere. For example, excessive vehicular movement during peak hours, an increase in air pollutants is likely to increase during daily construction activities. Air pollution can occur in local areas due particulate matter emission from the ongoing construction of houses, buildings and multi-storied apartments, flyovers, widening of roads and highways, discharge of polluted gas from excess traffic as well as lack of rain. The study was conducted w.r.t. some the main air pollutants responsible for generating AQI worldwide and the data revealed that some of the pollutants under investigation, have shown a slight increase due to which the overall AQI levels was found to be in the poor range during winter session. This type of study could be expanded to other districts and regions, with a cross-nation study for more concrete results, and the survey time as well as the seasonal variations may be studied for better results.
Acknowledgement
This study is not funded by any organization either partially or fully.
Conflict of Interest
The authors declare that there is no any conflict of interest including any financial, personal or other relationships with other people or organizations that can influence this work.
Funding Sources
The author(s) received no financial support for the research, authorship, and/or publication of this article.
References
Beig, G.; Sahu, S. K.; Singh, V.; Tikle, S.; Sobhana, S. B.; Gargeva, P.; Murthy, B. S. Total Environ., 2020, 709, 136126.
This work is licensed under a Creative Commons Attribution 4.0 International License.
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