Public Health Threat Assessment of Vehicular Load Index-Induced Urban Air Pollution Indices Near Traffic Intersections In Central India

Objectives: To assess traffic vehicular load, levels of various air pollutants, their correlation at selected traffic intersections of Bhopal city and to suggest suitable public health measures. Methods: A transverse study was conducted by convenience sampling with equated distribution among vehicular load-based large (Group1:G1: 10 TI), medium (Group2:G2: 5 TI), and small (Group3:G3: 5 TI) traffic-intersections (TI) through a systematic stratified random selection of study sites to assess traffic vehicle load index (VLI). Results: VLI,G1 (cumulative mean: 16.31; day-time (DT): 19.03, DT range 11.68-51.49; night-time (NT): 13.59, NT range 11.7-18.0), VLI,G2 (cumulative mean: 0.965; DT:0.971, DT range 08.56-11.67; NT: 0.960, NT range 07.54-11.39), and VLI,G3 (cumulative mean: 06.17; DT:06.08, DT range 04.12-06.86; NT: 06.27, NT range 03.74-07.53). There is a significant intergroup difference of the mean (G1 vs G2: p=0.03); (G1 vs G3: p=0.002); (G2 vs G3: p=0.003). The range of VLI is found to be wide within G1 (DT; 11.68-51.49; NT 11.7-18.00) as compared to narrow range in G2 (DT; 8.56-11.67; NT7.54-11.39) and G3 (DT; 4.12-6.86; NT 3.74-7.53). Conclusion: High air pollution noted at TIs and associated exposure to unprotected commuters pose public-health risks. It has long-term health consequences requiring focused multidisciplinary preventive interventions.


Introduction
Air pollution has been posing long-term, medium-term, and short-term challenges since long to the public health authorities thereby adversely affecting air quality indices [1]. PM10 standards for the ecologically sensitive area as per National Ambient Air Quality Standards is 60 µg/m 3 for an annual time-weighted mean of a minimum 104 measurements in a year at a particular site taken twice a week, 24 hourly at uniform intervals. PM10 standards for 24 hours time-weighted mean is 100 µg/m 3 . There is a felt need to revise PM10 standards to ensure avoidance of air pollution through preventive interventions at multiple levels with a special focus on maternal and child health [2].
Many studies have conducted air pollution indices in an indoor environment, but the studies related to the outdoor environment are much needed [3][4][5][6][7][8]. In 2015, Government of India, together with IIT Kanpur launched the National Air Quality Index. In 2019, India launched "The National Clean Air Programme" with a tentative national target of 20-30% reduction in PM2.5 and PM10 concentrations by 2024, considering 2017 as the base year for comparison. It will be rolled out in 102 cities that are considered to have air quality worse than the National Ambient Air Quality Standards. The present study will identify the traffic load wise pollution indices and their interrelationship. Hence, this study shall enrich the understanding of the vehicular pollution load in Central India as per the important pollution indicators.
A transversal study was conducted at a Tertiary Health Care Centre, Bhopal, India from June to September, 2019 to assess traffic vehicular load, levels of various air pollutants and their correlation at selected TIs of Bhopal city, and to suggest suitable public health measures.

Sample collection
The systematic stratified random selection of the TIs was conducted by convenience sampling with equated distribution among load-based large (Group1-G1), medium (Group2-G2), and small (Group3-G3) TIs (total 20). Vehicle load index (VLI) was assessed using "vehicular indices calculation matrix datasets." The vehicle load was determined herein by the exclusive VLI developed in this study assuming the load of each twowheeler, three-wheeler, cars, medium vehicle, and the heavy vehicle being 1.0, 1.5, 2.0, 2.0, and 6.0, respectively. The number of vehicles passing through each studied TIs was assessed lane wise as a mean of three readings at day-time (DT) and night-time (NT) for three days inclusive of last day being the reading date for all the air pollutants using calibrated Ambee Air Quality Monitor TM. The total number of TIs (n=20) included in the study were distributed in high traffic areas (G1: n=10), medium traffic area (G2: n=05), and low traffic area (G3: n=05). These included signaled (S) TIs (G1:07; G2:05; G3:01), semi-signaled (SS) TIs (G1:01; G3:01), non-signaled (NS) TIs (G1:02; G3:03S) (Tables 1 and 2).   the meteorological conditions prevailing on the days of data collection included temperature, humidity, dew, wind speed, air pressure, ultraviolet radiation, and visibility. The inclusion criteria for the study were randomly selected ten large, five medium, and five small traffic transactions. The convenient sampling was done twice a day for three consecutive days at each of the randomly selected sites. The list of these categories was prepared based on the pilot study undertaken for the overall load of traffic transactions at ten intersections of Bhopal distributed in all of its geographical zones. Those not listed in the randomly selected list of traffic transactions were excluded from the study. The portable digital device used for assessing various pollution parameters in the study was Ambee Air Quality Monitor TM .

Study sites
Twenty TIs were chosen in Bhopal city as per inclusion and exclusion criteria. Based on the traffic load, these TIs were divided into large, medium, and small. Various atmospheric pollutants studied included PM 2.5, PM 10, HCHO, CO 2 , etc., were monitored using Ambee Air Quality Monitor TM . Vehicle at the intersections was further divided into two-wheeler, three-wheeler, cars, heavy, and medium vehicles. Traffic load at each lane of each of the TIs was calculated for three consecutive days with the last day being data collection day for meteorological and air pollution parameters as well. The VLI was assessed as described above. The study was carried out at DT from peak traffic hours of 10 AM to 12 PM and at night from 6 PM to 8 PM. Random quick interviews were also conducted among pollution under control (PUC) check service provider, car service agencies, roadside tyre puncture repair shops, and traffic constables in each of these categories (G1, G2, G3).

Statistical analysis
All data entered were analyzed using SPSS (Statistical Package for Social Science) Version 20 (IBM Corp, Armonk, USA).

Cumulative range values of gaseous particles, particulate matter, and submicron particles
The cumulative range values of DT and NT were also assessed (

Intragroup correlation
The intragroup Spearman's rank correlation coefficient is found to be significant in some groups (PM2. Spearman's rank correlation coefficient for cumulated group TIs among remaining sites was found nonsignificant for groups namely VLI vs PM10, PM10 vs TVOC, PM10 vs CO 2 and PM10 vs HCHO ( Table 3).

Discussion
Our study observed range of site mean for G3 (3.93-7.19), G2 (8.05-11.53), G1 (11.69-34.74) are consecutively ascending in nature similar to the observed DT (G3-6.08, G2-9.71, G1-19.03), night time (G3-6.27, G2 -9.60, G1-13.59), and overall group mean (G3-6.17, G2-9.65, G1-16.31) ( Table 1). Similarly, a Madurai-based study 17 [9] has specifically underlined the importance of PM10 for vehicle-related pollution. The present study has also found highly increased PM10 in some of the TIs of G1, G2, and G3 groups [(G1/1: PM10, 1369.25); (G2/5: PM10, 113.25), and (G3/2: PM10, 600.65); Table 6]. While this study assessed VLI also as an indicator of traffic intersection-wise pollution (Tables 1, 2, and 7). Similarly, another study [10]  PM10 concentration was found to be raised due to local vehicular traffic in Finland in a study conducted by the Finnish Meteorological Institute [12], whereas PM2.5 concentration was assessed to be high at highwaysbased transport regions. The present study similarly infers that the increasing traffic load across traffic intersections in the city with expanding developmental initiatives under Capital Development Projects and other private developers shall pose further threats of higher air pollution levels in the years to come with seasonal variations challenging the public health scenario.
Seasonal trends of summer, autumn, winter were assessed in the Republic of Korea [13] by (686.9-701.5 ppm). These findings are in resonance with the findings of the present study. A study in Seoul Metropolitan Subway Stations at Han Yang University, Seoul [14] similarly found PM10 and PM2.5 to be higher than permissible levels of 150 μg/m 3 and 35 μg/m 3 , respectively, which were significantly higher than those at ground level (p<0.05). These Korean studies highlight the need to generate evidence of air pollution by on-road vehicles and related adverse consequences on human health across the spectrum of demographic profiles. The University of Porto, Portugal [9] collected data of DT and NT for PM10, PM2.5, and PM1.0 and found these to be on a higher level with PM10 (DT mean 125+73 μg/m 3 ; NT mean 110+71 μg/m 3  The present study focused on urban sites during one season only but higher levels of pollution were seen in traffic intersections under the classified categories (Tables 4 and 5). Contrastingly, the study of two Beijing sites, namely Chegongzhuang and Tsinghua, were assessed [20] for PM2.5 and found ranging between 37 and 357 μg/m 3 and found PM2.5 to be highest in winter and lowest in summer. It is observed in an Australian study [21] that the concentration of particulate matter proportionately decreases for PM2.5 with increasing distance from road reaching to 40% of that level at 150 m distance.
A review report by Central Pollution Control Board, CPCB [22]

Conclusions
The present study developed a new index namely VLI, which shall be more realistic to be adopted in the future for assessment of vehicular traffic concentration. The assessed increased levels of PM10, TVOC, CO 2 , and HCHO at all TIs under study including high, medium, and low traffic areas indicate moderate to severe public health threats to the resident community, commuters, nearby schools, and other people-centric facilities. These may lead to cough, asthma, bronchitis, stroke, and premature death among the exposed population as per their demographic and epidemiological profile. The presence of submicron particles (>0.25 μm, >0.3 μm, >0.5 μm, >10 μm) in almost all sites of traffic intersections in DT and NT indicates public health threats due to deposition of these particles into alveoli leading to irreversible pulmonary damage. Hence, there is a felt need for comprehensive strategic pollution prevention and control policy-based initiatives for primary prevention-based public health interventions in varied geological settings, especially in developing nations.

Additional Information Disclosures
Human subjects: All authors have confirmed that this study did not involve human participants or tissue. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue.

Conflicts of interest:
In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.