Respiratory Morbidity of Roadside Shopkeepers Exposed to Traffic-related Air Pollution in Bhopal, India

Background. Traffic-related air pollution (TRAP) is a major source of ambient air pollution in urban areas. Shopkeepers of heavily trafficked roadside shops are persistently exposed to high levels of TRAP. Objectives. To estimate the prevalence of respiratory morbidity in shopkeepers of shops in heavily trafficked roadside areas in Bhopal city (India) and to determine any association with long term exposure to TRAP. Methods. This cross-sectional study was conducted among 251 shopkeepers working in roadside shops of three major traffic corridors in Bhopal city. The demographic profile and prevalence of respiratory morbidity were collected by administering a validated questionnaire. The total exposure period (TEP) to TRAP was calculated for each individual by multiplying their work duration (in years) and average working hours per day. Odds ratios were calculated to estimate the association of TEP with respiratory morbidity. Results. The age of the study population was 44.8±13.5 years old and 95% were male. Nearly 55% of the shopkeepers reported at least one respiratory symptom. The prevalence of bronchial asthma, chronic bronchitis, breathlessness, and cough was 3.6% (95% confidence interval (CI): 1.9–6.7), 13.9% (95% CI: 10.2–18.8), 41.8% (95% CI: 35.9–48.0), and 18.3% (95% CI: 14.0–23.6), respectively. The adjusted risk ratios of bronchial asthma 2.17 (95% CI: 0.35–13.41), chronic bronchitis 1.42 (95% CI: 0.58–3.48), breathlessness 1.71 (95% CI: 0.94–3.11), and cough 0.97 (95% CI: 0.47–2.03) for those with a TEP over 100. Conclusions. Shopkeepers working in heavily trafficked roadside shops suffer from respiratory morbidity and the risk increases with higher TEP. Total exposure period is a valuable indicator to estimate the effects of long-term TRAP exposure. Informed Consent. Obtained Ethics Approval. The study was approved by the Institutional Ethics Committee of the National Institute for Research in Environmental Health (Bhopal, India). Competing Interests. The authors declare no competing financial interests.


Introduction
Outdoor air pollution accounted for 6% of the total disease burden in India in 2016. 1 Traffic-related air pollution (TRAP) is the main source of ambient air pollution in the majority of Indian cities. Motor vehicle exhaust emits diverse pollutants, including particulate matter (PM), lead, carbon monoxide, sulfur dioxide, oxides of nitrogen, unburned fuel, partly oxidized hydrocarbons, benzene, and polycyclic aromatic hydrocarbons. 2 Particulate matter and other components of vehicular exhaust penetrate the lung and initiate inflammation, a key step towards developing TRAP-induced adverse health effects. 3 The adverse health effects of TRAP are usually greater than industrial pollutants, as TRAP is released near ground level and remains there for longer periods, especially where roads are enclosed by high-rise buildings. Epidemiological studies have established the adverse health effects of TRAP exposure and its association with higher cardiorespiratory morbidity and mortality. 4 Individuals working or residing adjacent to roads with heavy traffic are persistently exposed to high levels of TRAP. The literature on the effects of chronic TRAP exposure on respiratory morbidity among roadside shopkeepers in India is sparse. 5, 6 Bhopal city is the capital of Madhya Pradesh state and is situated in central India. Bhopal has a subtropical climate; hot summers, cool and dry winters, and a humid monsoon season. Due to rapid urbanization, traffic volume in Bhopal city has increased Research over the last two decades and TRAP is major source of ambient air pollution in the city. 7 The aim of present study was to estimate the prevalence of respiratory morbidity in shopkeepers working in heavily trafficked roadside shops in Bhopal city and to determine its association with duration of work, a surrogate for long-term exposure to TRAP.

Methods
A cross-sectional descriptive study was carried out in Bhopal. The study was approved by the Institutional Ethics Committee of the National Institute for Research in Environmental Health (Bhopal, India). Bhopal city is divided into two distinct parts: the old and new city. The roads of the old city are narrow, congested and have a high volume of heterogeneous traffic. Remote sensing and geographic information system-based mapping demonstrate that major traffic corridors of Bhopal city are responsible for poor ambient air quality. 8 In the present study, we included road-facing shops located on either side of three major traffic corridors of old Bhopal City ( Figure  1). Area I was located around Hamidia Road, a well-known congested and busy road of old Bhopal city. The intercity bus terminal and rail station are situated on this road. The vehicles on Hamidia Road include passenger cars and heavy vehicles and this area has an estimated traffic volume of 72,000 passenger car unit (PCU). 9 Area II was located at Bairagarh Road, a part of the national highway connecting Bhopal city with Indore, another major city in Madhya Pradesh. Vehicle traffic on this road is mainly comprised of heavy vehicles and the estimated traffic volume is 19,000 PCU. 9 Area III was New Market, a commercial hub of Bhopal city. This market is encircled by major traffic corridors and the shops are located within 100 m from either roads. The vehicles on this corridor are mostly comprised of passenger cars and the estimated traffic volume is 51,000 PCU. 9 Shops in area I mostly deal with spare parts of machinery and electrical goods, whereas shops in areas II and III are primarily involved in the garment business.

Study population
Shopkeepers from the three study Research areas were approached to participate in the present study. We enrolled only shop owners who were actively involved in the management of their shops, to ensure that this would reflect actual exposure. Other shop employees were excluded as they often change jobs, thus their actual exposure to TRAP could not be determined.
Restaurant owners were also excluded as they might have additional exposure to kitchen fumes. The nature of the study was explained and verbal consent was obtained from each participant prior to data collection.

Data collection
Information on various respiratory symptoms was collected using a pre-validated Hindi translation of the Indian Study on the Epidemiology of Asthma, Respiratory Symptoms and Chronic Bronchitis (INSEARCH) questionnaire. 10 The diagnosis of bronchial asthma and chronic bronchitis was established as instructed in the INSEARCH questionnaire. The diagnosis of bronchial asthma was established by affirmative responses to a history of wheezing or tightness of the chest, plus one of the following: a history of previous diagnosis of asthma, an attack of asthma and/ or use of medication for asthma in the past 12 months. Similarly, the diagnosis of chronic bronchitis was based on presence of cough with expectoration for > 3 months and at least one of the following: cough first thing in the morning and/or ejecting phlegm from the chest in the morning. Breathlessness was defined as an affirmative response to at least one of the following four criteria: breathlessness in the morning, breathlessness on exertion, breathlessness without exertion, and/ or breathlessness at night. Cough was defined as the report of cough either in the morning or at night.

Sample size calculation
A previous study from Bangalore (India) reported a 12.4% and 32.2% prevalence of cough and breathlessness in roadside shopkeepers, respectively. 5 Based on the above observations, we expected that the prevalence of either cough or breathlessness in our study population would be 20%.
With a sample size of 251 subjects and a margin of error set at 5%, we used the formula n = Z 2 * P * (1-P) / d 2 , where Z was the level of confidence (95%), P was the expected prevalence (20%), and d was the allowable error (5%).

Statistical analysis
All baseline variables and outcomes were summarized as percentages, median with interquartile range (IQR), and mean ±standard deviation. The prevalence of respiratory symptoms with 95% confidence interval (CI) was calculated based on the Wilson score method. The association of respiratory symptoms with location De et al The prevalence of respiratory morbidity increased with higher TEP and the highest risk was observed for breathlessness ( Table 2). The association of different respiratory symptoms with TEP, age, and smoking are presented in Table 3. Smoking was strongly associated with higher respiratory morbidity, especially for chronic bronchitis and bronchial asthma. After adjusting for age and smoking status, the log odds for having respiratory morbidity showed increasing trends with longer TEP (Figure 2). Multivariate analysis showed an adjusted odds ratio of

Discussion
The present study assessed the prevalence of respiratory morbidity in roadside shop owners exposed to TRAP. The results highlight the high prevalence of respiratory morbidity among study participants and longterm exposure to TRAP was shown to be a risk factor.
Vehicular exhaust produces smallscale spatial variations in air pollution and affects the background air pollution level. The vehicular pollutant level gradually decreases with distance from roads and thus distance from roads is an important factor influencing the level of TRAP exposure. 11 Local climatic conditions, composition of traffic on the road (i.e. two-or three-wheeled vehicles, passenger cars, commercial vehicles, etc.), vehicle speed (use of brakes and accelerator), quality of fuel, average age of vehicles, etc. effect pollutant levels. Traffic congestion due to narrow and congested roads leads to lower vehicle speed, frequent slowdowns and accelerations and thus increases vehicle emissions and degrades ambient air quality. 12 Weak vehicular exhaust emission regulations, poor compliance to existing emission standards, poor fuel quality, and a large proportion of older vehicles play a crucial role in producing poor air quality in older highly populated cities in developing countries. Traffic-related air pollution is worse during winter months when temperature inversion occurs. A street canyon effect is formed in urban streets where adjoining high-rises and densely packed buildings prevent Table 3 Figure 3). 16-18

Figure 2 -Plots of total exposure period (TEP) and adjusted log of the odds ratio for different respiratory symptoms with confidence bands (dotted lines). A: Association of TEP with chronic bronchitis. B: Association of TEP with bronchial asthma. C: Association of TEP with breathlessness. D: Association of TEP with cough
The risk of cardiopulmonary mortality is higher for those residing near major roads and experiencing longterm exposure to PMs from TRAP. 19 Increased prevalence of respiratory symptoms and an excess FEV 1 decline have been observed in adult females chronically exposed to higher levels of PMs from automobile exhaust. 20 The severity of the health effects of TRAP vary due to different concentrations and compositions of pollutants, along with the genetic susceptibility of the exposed population. 21   Research traffic police personnel with > 8 years exposure to TRAP had lower lung function as compared with those with <8 years exposure. 24 A limitation of the present study was that lung function was not evaluated and there was a lack of female shopkeepers and hence female study subjects.
The INSEARCH questionnaire used in the present study was developed to assess the overall burden of chronic respiratory diseases in India. The original INSEARCH study reported the prevalence of asthma and chronic bronchitis in adults as 2.05% and 3.49% respectively. 10 In the present study, the prevalence of all respiratory symptoms, including bronchial asthma and chronic bronchitis in shopkeepers was higher compared to the INSEARCH study.

Conclusions
The present study demonstrated that shopkeepers working in congested and heavily trafficked roadside shops suffer from respiratory morbidity and the risks are higher for those with longer TRAP exposure. In addition, it showed that TEP can be a valuable indicator to assess the cumulative effects of TRAP exposure. There is a need to increase the awareness of individuals working or living near heavily trafficked roads of the adverse health effects of TRAP exposure and to promote measures such as glass doors on road-facing fronts to reduce direct exposure. Finally, measures to reduce traffic congestion, widen urban roads, promote the use of cleaner fuels, and prohibition of polluting vehicles can help to reduce ambient TRAP.