A Comparative Study of Respiratory Effects of Air Pollution in Urban Dwellers and Biomass Pollution in Villagers

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A Comparative Study of Respiratory Effects of Air Pollution in Urban Dwellers and Biomass Pollution in Villagers


Amity International School, New Delhi &


Professional Reviewer: Levente Pap


Urban air pollution is largely attributed to vehicular and industrial emission whereas in rural areas, the air pollution mainly results from the combustion of biomass fuels and stubble burning.  The primary aim of this study was to compare the respiratory symptoms and abnormal lung functions between the urban street dwellers exposed to air pollution and rural population exposed to biomass pollution as both can cause a number of lung diseases. This cross-sectional study included urban street dwellers in Delhi and rural population in the villages of Haryana.  Demographic profile was recorded and information was collected using the Medical Research Council 1986 questionnaire on the occurrence of respiratory symptoms. Screening Pulmonary Function Test was done using a vitalograph COPD6 spirometer. The study group is comprised of urban subjects (n=1078) of which 46.38% were males and 53.62% were females; and rural subjects ( n= 1066) of which 51.97% were males and 58.03% were females.  The study results showed that coughing was the commonest symptom in both the groups reported by 25.88% of urban subjects and 27.38% by the rural subjects. Shortness of breath was the second commonest symptom reported by 22.82% and 14.75% of urban and rural subjects respectively. Abnormal PFT readings were observed in 26.71% of all the urban subjects and 27.01% of all the rural subjects which was similar in both the groups. The study concluded that the villagers exposed to biomass smoke have similar prevalence of respiratory symptoms and abnormal PFTs to the urban dwellers who are exposed to higher ambient air pollution.   


Pollution is defined as the contamination of environment by any chemical, physical or biological agents that modifies the natural characteristics of the atmosphere. Air pollution is characterized by an undesirable change in quality of air. According to a 2016 World Health Organization air quality model report about 92% of the world’s population lives in places where air quality level is below permissible quality.1   Inhalation represents the fundamental mechanism of exposure to airborne pollutants in humans.2   Particulate matter present in polluted air such as dust, smoke, pollen and volatile organic compounds can cause serious damage to the respiratory tract.  Not only can it worsen a pre-existing respiratory illness, but it can also provoke the development of other diseases such as asthma, chronic obstructive pulmonary disease, and lung cancer.3

The world is facing a global epidemic of chronic respiratory diseases which are responsible for 4.2 million deaths a year worldwide, nearly 80% of which occur in low or middle-income countries.4,5 The United Nations (UN) estimates that road traffic accounts for up to 90% of urban air pollution in developing countries.6 The United Nations Environment Programme (UNEP) also estimated that more than 600 million people in urban areas around the world were exposed to dangerous levels of air pollutants generated by traffic.7 Residents of cities with highly polluted air suffer more from heart disease and respiratory problems than those in cities with cleaner air.8

Air pollution has been commonly perceived as an urban problem associated with motor vehicles and industries. However, in developing countries, air pollution tends to be high in rural areas where biomass fuels are burned by many households for cooking.9,10 Indoor cooking and heating with biomass fuels (agricultural residues, dung, straw, and wood) or coal produces high levels of smoke that contain various health damaging pollutants.   The production and use of biomass fuels are done under suboptimal conditions, which contributes enormously to air pollution and greenhouse gas (GHG) burden.11 Exposure to biomass air pollution may be responsible for nearly 2 million deaths in developing countries and about 4% of the global health burden.12 In India, there is a yearly death toll of 662,000 due to biomass fuel exposure, and with these alarming figures India tops the list of fuel-related deaths in the South Asian region.13

In this study, we have tried to compare the respiratory effects of air pollution and biomass fuel amongst the urban street dwellers, and the villagers respectively; and to spread awareness about the harmful effects and early warning signs of air pollution in the community.     

Aims & Objectives

  1. To compare the respiratory symptoms and abnormal lung functions between and urban street dwellers exposed to air pollution and rural population exposed to biomass pollution.
  2. To spread awareness about the harmful effects and early warning signs of pollution in the community.
  3. To spread awareness about the preventive measures against pollution.
  4. To refer people with abnormal lung functions for further medical examination  at the nearest health facility.

Materials & Methods

Study Group

This survey was conducted from September 2016 to February 2017. All interviews and examinations took place in community centres and households of the study populations. The study cases were non-smoking men and women between the ages of 9-83 residing in the slum areas of Delhi comprising the urban area and households using the biomass fuel in villages of Haryana comprising the rural area.  

Consent was taken from every subject to undergo the whole survey. The whole process was explained in detail to each subject in their own language to allay any apprehension or fear. They were given individual interviews using a standardised questionnaire. Information was collected on the occurrence of the six most relevant respiratory symptoms modified from the MRC 1986 questionnaire as follows:14

  • Frequent cough for 3 months (S1)
  • Phlegm in cough for 3 months (S2)
  • Shortness of breath (S3)
  • Wheezing or whistling sound in breathing (S4)
  • Woken up in the night due to breathing difficulty (S5)
  • Coughing up blood in the sputum (S6)
  • History of more than 1 episodes of respiratory ailments in past 3 years (S7)

The questionnaire included factors such as age, weight, height, sex, smoking history, occupation, and domestic cooking fuels used in previous 5 years. The urban dwellers using biomass fuel were excluded from the study. Those with any of the following within the previous two months were excluded as they were unable to undergo pulmonary function tests using a spirometer: thoracic or abdominal surgery, heart attack, current tuberculosis, eye surgery or hospitalisation for a cardiovascular problem.     

Pulmonary Function Tests

The lung functions of the subjects were evaluated using COPD6 spirometer supplied by the Cipla, a pharmaceutical company. The subject’s age in years, height measured in standing position without shoes in centimetres (cm) and weight measured in kilograms (kg)  were fed into the spirometer. The machine automatically calculated the normal predicted values of spirometry variables of the individual subject corresponding to his/her age, weight and height using its in-built software.

Fig 1: COPD 6 vitalograph.

Fig 2: Spirometry being performed by a rural woman exposed to biomass fuel smoke.

The procedure for performing pulmonary function tests was explained to the subjects in detail and they were made familiar with the device used to perform the tests. The procedure of the pulmonary function test was demonstrated to the subject prior to the commencement of each test and maximum effort on behalf of the subject was emphasized. The subjects were instructed to keep the mouthpiece tightly within their lips. They were asked to breathe in and out normally into the mouthpiece. Then, the subject was asked to take a deep breath to fill their lungs to the maximum capacity and then blow out into the mouthpiece as quickly as possible to full exhalation. The parameters recorded were Forced Vital Capacity [FVC] in litres, Forced Expiratory Volume in first second [FEV1] in litres, and FEV1/FVC%.  All the subjects made three such attempts and the best of them was selected. The spirometry indices were calculated in percentage using best out of 3 technically satisfactory performances as per recommendations of American Thoracic Society.14 The abnormal PFT was classified as Obstructive Pattern if FEV1% (Ratio of FEV1% and FVC was less than 80%) and Restrictive Pattern if both FEV1 and FVC were less than 70% of predicted values while the FEV1% was equal to or more than 80%.

Statistical Analysis

Statistical analysis was done by using the p Value calculator for two population proportions available online at the site www.socscistatistics.com.   The mean values of demographic profile of two groups were compared using Medcalc statistical software available online at the site www.medcalc.org. A p value of <0.05 was considered statistically significant.


Study Group

This was a cross sectional observational study. A total of 1078 street dwellers in Delhi which included 500 (46.38%) males and 578 (53.62%) females who were exposed to ambient air pollution comprised the urban population group.  A total of 1066 villagers in Haryana which included 554 (51.97%) males and 512 (58.03%) females who were exposed to burning of biomass fuel for at least 5 years comprised the rural population group (Table 1). Subjects aged up to 19 years were considered as children.  There were 227 children in the urban group and 215 in the rural group. As children formed a very small number, they were further not classified into male and female groups and also not compared with adult population.

Demographic Profile

The age, height, and weight of urban males compared with rural males and urban females compared with rural females were similar.  The age of urban males (Mean ± SD in years 38.6 ± 16.54) and age of rural males (Mean ± SD in years 38.69 ± 16.2) with a p Value <0.697;  the height of urban males (Mean ± SD in cm 170 ± 17.84) and height of rural males (Mean ± SD in cm 168.6 ± 10.2) with a p Value <0.168; the weight of urban males (Mean ± SD in kg 74.1 ± 17.84) and weight of rural males (Mean ± SD in kg 74.13 ± 17.8) with a p Value <0.906 were similar with no statistically significant difference in the demographic profile of the two groups.  The age of urban females (Mean ± SD in years 37.57 ± 16.54) and age of rural females (Mean ± SD in years 36.76 ± 15.89) with a p Value <0.437; the height of urban females (Mean ± SD in cm 158 ± 9.57) and height of rural females (Mean ± SD in cm 158 ± 11.53) with a p Value <0.44; the weight of urban females (Mean ± SD in kg 63.35 ± 16.01) and weight of rural females (Mean ± SD in kg 63.09 ± 15.1) with a p Value <0.711 were similar with no statistically significant difference in the demographic profile of the two groups.  

Respiratory Symptoms

All the subjects were asked 7 questions about their respiratory symptoms (Tables 2,3,4).


Frequent Cough for 3 months or more was the most common symptom in all the urban and rural subjects reported as 25.88% and 27.38% respectively.  Urban males reported cough in 29% subjects and rural males in 26.55%. The female population also reported cough as the most common symptom which was statistically significant in the rural female subjects as compared to urban females, 28.57% and 23.18% (p Value <0.022).


Phlegm in the cough for 3 months or more was reported by urban and rural subjects as 9.29% and 7.88% respectively, but was significantly higher by the urban males as compared to rural males, 10.08% and 6.14% respectively (p Value <0.003).  Urban females reported phlegm in sputum in 8.82% and rural females in 9.77% subjects.

Shortness of breath

Breathing difficulty was the second overall the most symptom in both urban and rural subjects including in both the sexes.  The shortness of breath of breath was reported by 22.82% of total urban and 14.75% of total rural subjects. The male subjects in urban and rural cohorts reported breathing difficulty   25.00% and 22.92% respectively. Rural females reported breathing difficulty more than the urban females 25.39% vs 20.93 (p Value < 0.040) which is statistically significant.


History of wheezing or whistling sounds was reported by 13.08% urban and 11.92% rural subjects.  Urban males reported statistically significant higher complaint of wheezing as compared to rural males 14.40% and 11.01% respectively (p Value < 0.049).  Urban and rural females reported wheezing in 11.94% and 12.89% respectively.

Sleep disturbance due to breathing difficulty

Sleep disturbance and woken up due to breathing difficulty was reported by 19.12% urban and 15.10% rural subjects.  The urban and rural males in 16.40% and 14.26% respectively, and urban and rural females in 13.49% and 16.02% subjects respectively reported disturbance in sleep due to breathing difficulty.


Coughing up of blood in the sputum was reported by 0.18% urban and 0.19% rural subjects. Only 0.40% urban males and 0.39% rural females reported the complaint of hemoptysis. The urban females and rural males did not give any history of hemoptysis.

Previous History of Respiratory Ailments

History of respiratory ailment more than once in previous 3 years was reported by 15.77% urban subjects statistically significantly higher than by 8.35% rural subjects ( p Value 0). Urban males reported previous respiratory ailments significantly higher than rural males 18.80% vs 6.86% ( p Value 0) similar to urban females significantly reporting more than the rural females 13.15% vs 9.96% ( p Value < 0.050).

Abnormal Pulmonary Function Tests

A detailed analysis of abnormal PFT is described in Tables 5 to 10.  Abnormal readings of PFT were observed in 26.71% urban and 27.01% rural subjects without any significant difference (p Value < 0.436).  Obstructive pattern was recorded in 19.11% urban and 19.60% rural subjects (Table 5). The urban and rural male subjects recorded similar abnormal lung functions (Table 6). The rural females had significantly higher obstructive pattern as compared to urban females reported as 21.88% and 17.82% (Table 7) and also in comparison to rural males reported as 17.51% (Table 9).  The urban and rural males reported obstructive pattern in 20.60% and 17.51% subjects respectively (Table 6). Restrictive pattern was observed in 7.61% urban and 7.41% rural subjects (Table 5). The urban males had a significantly higher restrictive pattern as compared to urban females (Table 8). Abnormal PFT were recorded in 29.51% (67/227) urban and 25.58% (55/215) rural children without a significant difference (p Value< 0.113).  However, the obstructive pattern was observed significantly higher in urban children than in the rural children; 25.11% and 18.12% respectively (Table 10).


Air pollution is a major environmental risk factor for global public health. The World Health Organization (WHO) estimated that urban air pollution could cause 3.7 million of premature deaths worldwide in 2012.6  Rural indoor air pollution due to biomass fuels is ranked 10th amongst most preventable risk factors for global disease  burden and 4th when only developing countries are considered.12  The WHO states that more than 1.6 million deaths per year and 38.5 million disability-adjusted-life years are due to  biomass fuel exposure which predominantly affects women and children.15   It is estimated that approximately 50% of the world’s population and 75% of Indian households use solid biofuels primarily in the form of wood and cow dung.11  It is now increasingly believed that the harmful health burden due to exposure from pollutants released during the combustion of solid biomass fuels in rural indoors equals or even exceeds the burden contributed by urban outdoor air pollution.16  While traffic is a major pollution source in big cities, the use of biomass fuel for cooking is the main source of pollution in most rural areas.17 (Fig. 4)

Fig. 4: Biomass pollution caused by cooking on a country-made burner (Chulha) using fire wood.

In our study, 26.71% urban street dwellers in the city of Delhi were found to have abnormal lung functions.  In a study conducted in the urban areas of Kolkata, three dispensaries were surveyed which showed that respondents with respiratory diseases (85.1%) had outnumbered waterborne diseases (14.9%).18   It is a recognized fact that the residents of cities with highly polluted air suffer more from respiratory problems than those in cities with cleaner air.9   In most Indian cities, real measures against air pollution from road traffic are not implemented or applied. The WHO estimated that 84000 deaths are directly attributable to outdoor air pollution in Indian cities.17

This study showed that the likelihood of causing lung diseases by urban ambient air pollution and rural biomass pollution was similar.  Abnormal PFT readings were observed in 26.71% of all the urban subjects and 27.01% of all the rural subjects which was similar in both the groups.  This could be because in a developing country like India, both rural and urban areas are equally affected by pollution.19   

In rural India, the prevalence of biomass fuel use is 90%, of which wood accounts for 56%, crop residues for 16%, and dung-cakes for 21%.20  The crude biomass fuels produce 10–100 times more hazardous particulate matter than the modern fuels.21-23  In our study, the majority of households   burn solid fuels in inefficient indigenous devices like chulhas, often in kitchens that are poorly ventilated, resulting in very high exposure to multiple toxic pollutants.16       In our study, the obstructive lung function tests suggestive of obstructive airway disease such as bronchial asthma and chronic obstructive pulmonary diseases (COPD) were observed in 19.11% urban and in 19.6% rural population with no significant difference between the two groups.   However, the rural females had significantly higher obstructive patterns suggestive of obstructive airway disease as compared to urban females reported as 21.88% and 17.82% (Table 7) and also in comparison to rural males reported as 17.51% (Table 9). The present study shows that exposure to biomass smoke in rural areas is the most common cause of non-smoker COPD as also reported by Salvi et al.24   In another study, Hu et al. reported exposure to biomass fuel smoke was associated with a 2.3- fold increased risk of COPD.25    In developing countries, about 50% of deaths from COPD are attributed to biomass smoke, of which 75% are of women.24

In this study, abnormal PFT readings were observed in 26.71% of all the urban and 27.01% of all the rural subjects which was similar in both the groups.   Abnormal PFT were observed in 29.51% urban and 25.58% rural children, being equally high in both the groups. The obstructive pattern was significantly higher in urban children as compared to rural children reported as 25.11% vs 18.12% (Table 10).  In a recent study in rural women, it was found that pulmonary function parameters were significantly reduced in biomass fuel users as compared to clean fuel users.26,27   In a study conducted in South Indian State of Karnataka, it was observed that the lung function parameters   were significantly lesser in the group exposed to biomass fuel.28 Studies both in India and other countries have confirmed that exposure to biomass fuels has a significant association to decline in objective lung function parameters.29-32?

In this study, coughing was the commonest symptom in both the groups reported by 25.88% urban and 27.38% rural subjects.  Shortness of breath was the second commonest symptom reported by 22.82% and 14.75% of urban and rural subjects respectively.  These two symptoms were significantly higher amongst rural females as compared to urban females. The Urban males had significantly higher symptoms of phlegm and wheezing as compared to rural males (Table 4). However, the rural population reported higher rate of wheezing compared to urban areas in the other studies from Nepal, Canada, India, China and Guatemala.29,33-39  Low level of education, ignorance of health care providers, lack of awareness of hazards of air and biomass pollution, non-availability of spirometry are the important factors of under-diagnosis or delayed diagnosis of respiratory diseases in both the urban and rural groups in our study. People in the developing countries often consider wheeze, breathlessness and phlegm to some extent as normal which may result in under-reporting of symptoms.

There are several strengths of this study. We utilized both the modified MRC 1986  questionnaire and spirometry to identify people with respiratory diseases. Unlike case-control or hospital-based studies, our exhaustive community-based sampling provided actual prevalence data for respiratory symptoms and pulmonary function values for the population.  This is the first study comparing the effects of urban ambient air pollution with rural biomass pollution and revealed that both are equally harmful for lungs. There are also a few limitations of this study: the COPD6 vitalograph spirometer is primarily used as a screening test for lung functions. A validated PFT is required for confirmation of diagnosis.  However, an abnormal PFT recorded by COPD6 spirometer raises a very high possibility of having a lung disease. A proportion of patients may have underperformed during the PFT resulting in restrictive pattern even though they may be a having normal lung functions. Therefore, the restrictive dysfunction could be an overestimated number in the study. This study also did not perform measurements of biomass smoke exposure and environmental pollution.  


We found associations between exposures to ambient air pollution and biomass pollution and reduced lung function in the urban and rural areas respectively in equal proportion leading to harmful effects on the lungs. More than 25% of both urban and rural population is likely to be affected with air pollution related lung diseases based on their symptoms and abnormal lung functions.  This is a significantly high alarming number. The likelihood of causing lung diseases by urban ambient air pollution and rural biomass pollution is similar without any significant difference. The villagers are equally susceptible to harmful effects of air pollution caused by biomass. Frequent cough for 3 months or more and shortness of breath were the commonest symptoms in both urban and rural subjects. People with these two symptoms should undertake early medical check-up to rule out the possibility of asthma and COPD.    The study points to a need for creating awareness on the issue of rural biomass pollution in addition to making available more efficient stoves and clean fuels and highlighting the importance of proper ventilation and chimneys in the cooking areas. Use of clean fuels such as solar cookers, biogas and LPG needs to be considered. Incorporating the ‘universal access to clean fuel’ agenda within the broader framework of rural development and raising the standard of living will go a long way in reducing disease burden.


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