For verification of this paper, please visit on http://www.socialresearchfoundation.com/innovation.php#8

Air Pollution, according to the World Health Organisation, is contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere [1]. Its sources could be both anthropogenic and natural. Anthropogenic sources include burning of traditional biomass such as wood, crop waste etc; burning of fossil fuels, fumes from paint, hair spray etc;waste deposition in landfills produces gases like methane; agricultural activities, etc. Its natural sources include dust from land where there is no or little vegetation, methane emission by animals during digestion, radioactive decay in Earth’s crust and mantle, wildfires, volcanic activities, etc.There is widespread exploitation of natural resources in the name of development without conducting any consequence analysis. It results in deforestation, release of toxic materials which further leads to unhealthy environment to live in. This is more evident in cities where rapid urbanisation is taking place. Growing urbanisation is an inevitable process, especially for developing countries. This is then followed by growth in other sectors such as transport, construction, manufacturing, etc. In India most of metro cities are unplanned one which leads to higher population density towards the city centre [2]. The high population density resultsin more transportation activities [3], consequently more pollution. Air pollution has very alarming effects on human health. It is a significant risk factor for respiratory infections, heart diseases and lung cancer. It can also cause harm to animals and crops [4,6]. According to a report, “in India, air pollution is the third highest cause of death among health risks”. Because of it, life expectancy has gone down by 2.6 years. Growing evidence suggests that air pollution exposure may be associated with reduced IQ scores, impaired cognition, increased risk of psychiatric disorders such as depression, etc [5]. The effect of Air Pollution on human body vary depending on the type of pollutant and the length and level of exposure, as well as other factors including a person’s individual health risks and the cumulative impacts of multiple pollutants and stressors. Air Quality Index (AQI) is powerful tool which tells how clean or polluted air of a particular area is. Each country has their AQIs based on its air quality standards. In India, AQI was launched by the central government in 2014 as part of Swachh Bharat Campaign. There are generally five or six categories of AQI, ranging from Good/Safe to Severe. AQI works as an indicator of ambient air quality which general public could easily understand. It makes people aware of the detrimental effect of air pollution and stimulates them to take measures to reduce it on individual level.

Bishoi et al [7] proposed the EPA method for the computation of AQI (EPAQI). The technique involved index value calculation for each pollutant. Furthermore, the research involved the Factor Analysis method to calculate the New AQI (NAQI) encompassing the Principal Component Analysis (PCA), which was used to find out whether the air quality has worsened or improved over the months. Shivangi et al [8] performed a comparative study, wherein the various formulae and methodologies used in the computation of AQI were assessed. The study included an analysis of five different techniques to determine the most precise calculation methodology. Anikender et al [9] proposed a forecasting model to predict the AQI value which implemented the technique of Multiple Linear Regression and Principal Component Regression model. This research model included the usage of the past days’ AQI values. These values were computed using the EPA, 1999 formula. Sai Reddy et al [10] have assessed ambient air quality of Delhi. They have compared air quality for different seasons.

Materials and Methods

The data has been taken from Central Pollution Control Board (CPCB) directories. CPCB, along with its regional offices, undertakes real time continuous monitoring of vital air pollutants at different sites in India. The present study considers data from three monitoring stations of Jaipur City (Rajasthan) for three years (1^st Jan 2020-)

Study Area

Jaipur (26.55° N, 75.49° E) is the capital of Rajasthan. It is at the elevation of 431 m above the mean sea level and expands over an area of 467 sq. km. City is divided into 8 geographical zones with 91 wards. It is located in the semi-arid zone of India. It is characterised by high temperature, low rainfall and mild winter. Its mean temperature is 36°C. The normal rainfall of Jaipur is 600 mm. According to the Census 2011, its population density is 598 humans per sq. km. 

Data Set

For the present study, concentration of air pollutants, namely PM₁₀, PM_2.5, SO₂ and NO₂ for 3 years (2020-2022) has been extracted from CPCB’s archives. The daily data has been collected for three monitoring stations of Jaipur City, namely, Shastri Nagar, Adarsh Nagar and Police Commissionerate.

Methodology

Calculation of AQI involves two steps, first the formation of sub-indices of each pollutant and second the aggregation of sub-indices. The sub-indices for the individual pollutants are calculated for each monitoring station using their average concentration value over a 24-hour period and their health breakpoint concentration range. The worst sub-index value is taken to be the AQI for that particular location.

Individual AQI for pollutant in calculated by the formula (EPA, 1999) given below:

where

B_HI: Breakpoint concentration greater or equal to given concentration

B_LO: Breakpoint concentration smaller or equal to given concentration

I_HI: AQI value corresponding to B_HI

I_LO:  AQI value corresponding to B_LO

Finally, AQI = max (I_p); where p denotes different pollutants

Table 1: Proposed sub-index and breakpoint pollutant concentration for Indian Air Quality Index

AQI	Category	24hr. average (µg/m3)
		PM2.5	PM10	NO2	SO2
0-100	Good	0-200	0-100	0-80	0-80
101-200	Moderate	201-260	101-150	81-180	81-367
201-300	Poor	261-400	151-350	181-564	368-786
301-400	Very poor	401-800	351-420	565-1272	787-1572
401-500	Severe	800+	420+	1272+	1572+

PM2.5, PM10, SO₂ and NO₂ are the most significant air pollutants among other pollutants. Average concentration of ambient air pollutants PM2.5, PM10, SO₂ and NO₂ has been obtained season-wise for understanding the overall pollution level in Jaipur city.

Table2: Season-wise average concentration of pollutants from 2018 to 2022

Year	Season	PM2.5 (µg/m3)	PM10 (µg/m3)	NO2   (µg/m3)	SO2  (µg/m3)
2018	Winter	61.87	141.23	33.92	10.96
	Summer	60.93	172.17	32.82	9.64
	Monsoon	48.07	100.77	20.24	9.94
	Post Monsoon	61.01	141.41	39.39	11.28
2019	Winter	49.18	114.76	33.56	12.44
	Summer	51.74	140.30	33.13	12.73
	Monsoon	33.03	74.76	23.95	10.38
	Post Monsoon	58.69	120.01	39.47	12.82
2020	Winter	45.01	102.49	32.35	11.83
	Summer	34.17	85.85	17.51	12.17
	Monsoon	27.46	67.31	19.41	10.19
	Post Monsoon	66.30	140.40	43.62	12.27
2021	Winter	57.55	119.77	36.35	12.78
	Summer	56.76	124.74	27.00	13.69
	Monsoon	35.03	80.19	22.15	11.99
	Post Monsoon	65.74	130.43	44.47	11.81
2022	Winter	57.65	127.92	48.46	13.82
	Summer	77.68	181.74	60.86	14.11
	Monsoon	31.12	69.53	31.35	12.49
	Post Monsoon	57.82	112.38	48.36	14.17

Data obtained from monitoring of ambient air at three stations is used to calculate the Air Quality Index for critical parameter. The resultant correlation matrix between the pollutants PM2.5, PM10, SO₂ and NO₂ and AQI is tabulated in Table 2.

Table3: Correlation matrix of pollutants (2018-2022)

It can be seen that all pollutants considered, namely, PM₁₀, PM_2.5, SO₂ and NO_2, have a positive correlation with AQI. Clearly, PM₁₀ and PM_2.5 show significant correlation with AQI. It can also be noted that all the pollutants have a positive correlation with each other. It implies that a rise in the concentration of any of the pollutants will lead to the rise in the concentration of other pollutants as well.

Over the span of five years, AQI has been observed. The years 2018, 2019 and 2022 were normal years, whereas years 2020 and 2021 were COVID-affected years. There was hardly any sector which was not affected by coronavirus pandemic. During pandemic years, there was bare minimal movement of people. Industrial activities too got stalled. Air Pollution remained at minimum levels during these two years, which also reflects in the graphs given below:

Chart 1: Daily computed values of AQI for the years 2018-2022

Overall pollution level is high during winters. This is because in winters, there is the presence of cold air. Cold air is denser and moves slower. Denser cold air traps the pollution and doesn’t allow it to disperse away. Thus, air pollution in winter remains in place for much longer. Fog conditions aggravate air pollution even more. It leads to smog (fog + Smoke). It makes the atmosphere difficult to breathe and harmful for health. In summers, generally air pollution levels are even higher as compared to winters. This is because of the widespread windblown dust and lack of rain. Rain acts as natural cleanser. Thus during monsoon, pollution levels are lower. Again, pollution levels tend to increase in post monsoon period.

1. www.who.int. World Health Organization 2. Chadchan, J. & Shankar, R., 2012. An analysis of urban growth trends in the post-economic reforms period in India. International Journal of Sustainable Built Environment, 1(1), pp.36–49. 3. Dadhich, P.N. & Hanaoka, S., 2012. Spatial investigation of the temporal urban form to assess impact on transit services and public transportation access. Geo-Spatial Information Science, 15(3), pp.187–197. 4. Cropper, M.L. et al., 1997. The Health Effects of Air Pollution in Delhi, India. The World Bank, (December 1997), p.40. 5. Allen, J.L.; Klocke, C.; Morris-Schaffer, K.; Conrad, K.; Sobolewski, M.; Cory-Slechta, D. A. (June 2017). "Cognitive Effects of Air Pollution Exposures and Potential Mechanistic Underpinnings". Current Environmental Health Reports. 4 (2): 180–191. 6. Singh HR, Sharma RC, et al (2014). A retrospective approach to assess human health risks associated with growing air pollution in urbanized area of Thar Desert, western Rajasthan, India. Journal of Environmental health science Engineering. 2014,12:23. 7. Biswanath Bishoi, Amit Prakash, and V.K.Jain, "A Comparative Study Of Air Quality Index Based On Factor Analysis And US-EPA Methods for an Urban Environment", Bishoi et al., Aerosol and Air Quality Research, Vol. 9, No. 1, pp. 1-17, 2009. 8. Shivangi Nigam, B. P. S. Rao, Navneet Kumar,and V. A. Mhaisalkar, "Air Quality Index – A Comparative Study for Assessing the Status of Air Quality", Research Journal of Engineering and Technology, pp. 267-274, 2016. 9. Anikender Kumar and Pramila Goyal, "Forecasting of air quality in Delhi using principal component regression technique", Atmospheric Pollution Research, Vol. 2 , pp. 436-444, 2011. 10. Sai Reddy, Pragya Verma and Mithilesh Waghulade, “Air Quality Index – A Study to Assess the Air Quality”, International Research Journal of Engineering and Technology (IRJET), Vol. 7, Issue 2, 2020 11. Central Pollution Control Board https://cpcb.nic.in/