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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 8  |  Issue : 2  |  Page : 71-75

Study of association between exposure to indoor air pollution and chronic obstructive pulmonary disease among nonsmokers in a North Indian population – A case–control study


1 Department of Respiratory Medicine, Maharani Laxmibai Medical College, Jhansi, Uttar Pradesh, India
2 Department of Respiratory Medicine, King George Medical University, Lucknow, Uttar Pradesh, India
3 Department of Respiratory Medicine, Dr. Ram ManoharLohia Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
4 Department of Pulmonary Medicine, Era's Lucknow Medical College and Hospital, Lucknow, Uttar Pradesh, India
5 Department of Community Medicine, Dr. Ram ManoharLohia Institute of Medical Sciences, Lucknow, Uttar Pradesh, India

Date of Submission04-Dec-2018
Date of Decision05-Jan-2019
Date of Acceptance10-Mar-2019
Date of Web Publication1-Jul-2019

Correspondence Address:
Dr. Hemant Kumar
Department of Respiratory Medicine, Dr. Ram Manohar Lohia Institute of Medical Sciences, Lucknow, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijrc.ijrc_52_18

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  Abstract 


Background: Chronic obstructive pulmonary disease(COPD) is one of the most killing diseases worldwide. Tobacco smoking is still the most common single cause of COPD, but in developing countries such as India, indoor air pollution is one of the common etiological factors for COPD. This study was done to find out the association of various indoor pollution and COPD, especially in women who are exposed most due to the burning of domestic fuel. Patients and Methods: This is a case–control study in which 164 spirometry-confirmed COPD patients and 328 matched controls were studied. Various types of indoor air pollution were compared between cases and controls. Results: Of 164cases, 72cases(43.9%) had regular exposure to indoor air pollution. Common types of indoor air pollution were biomass fuel, wood smoke, coal smoke, and stove smoke. The odds of having indoor pollution such as biomass fuel exposure, wood exposure, coal, and stove in COPD patients were 3.16, 2.70, 2.45, and 2.05, respectively, in comparison to the control group. Except stove exposure, other indoor air pollutions were statistically significant with P =0.001, 0.003, and 0.02, respectively. Longer time exposure in terms of number of years of biomass fuel exposure, wood exposure, and coal fuel exposure was statistically significant as compared to exposures in the control group with P =0.001, 0.0009, and 0.0006, respectively. Conclusion: Indoor air pollutants(biomass fuel, coal, and wood smoke) are associated with the development of COPD, especially in the female population.

Keywords: Biomass fuel, coal exposure, indoor air pollution, wood exposure


How to cite this article:
Madhurmay, Suryakant, Kumar H, Kumar S, Prasad R, Verma AK, Singh AK. Study of association between exposure to indoor air pollution and chronic obstructive pulmonary disease among nonsmokers in a North Indian population – A case–control study. Indian J Respir Care 2019;8:71-5

How to cite this URL:
Madhurmay, Suryakant, Kumar H, Kumar S, Prasad R, Verma AK, Singh AK. Study of association between exposure to indoor air pollution and chronic obstructive pulmonary disease among nonsmokers in a North Indian population – A case–control study. Indian J Respir Care [serial online] 2019 [cited 2019 Sep 15];8:71-5. Available from: http://www.ijrconline.org/text.asp?2019/8/2/71/261907




  Introduction Top


Chronic obstructive pulmonary disease(COPD) is a systemic disease which results from interaction between gene and environment. Smoking in any form(cigarette, beedi, hukka, and cigar, etc.) is a major environmental risk factor for COPD. Every smoker does not develop COPD in his life time, and hence, genetics also play a role in modifying the risk of COPD in smokers.[1] The diagnosis of COPD is done by spirometry in patients having respiratory symptoms and exposure of noxious particles. The presence of a postbronchodilator forced expiratory volume 1 s(FEV1)/forced vital capacity<0.70 confirms the presence of persistent airflow limitation. The severity of COPD is also assessed by spirometry as mild(FEV1>80%), moderate(FEV150%–79%), severe(FEV130%–49%), and very severe(FEV1<30%).

The WHO estimates COPD to be the 10thleading cause of disability-adjusted life-years in all countries. In worldwide, mortality due to COPD was 3.17 million in 2015 and out of it>90% of COPD deaths occurred in low-and middle-income countries.[2]

Worldwide, the primary cause of COPD is exposure to tobacco smoke but in developing countries such as India, other risk factors such as indoor air pollution is one of the major risk factors for COPD. Exposure to indoor air pollution can also affect the unborn child and represent a risk factor for developing COPD later in life. Indoor air pollution mainly consists of biomass fuel, wood burning, and stove smoke, etc., used for cooking, especially in developing countries such as India where it accounts for up to 75% of the domestic energy supply.[1]

Major biomass fuel used in India are firewood, dung cakes, agricultural crop residues(such as straw, grass, and shrubs), coal fuels, and kerosene used as fuel in the stove.[2] Out of total energy produced from domestic fuel, only 18% is used in cooking, whereas 74% of the energy is dissipated as waste heat. Burning biomass fuels emits toxic substances such as small solid particles of size<2.5 μm (PM2.5) which can penetrate deeply into the lungs. Common noxious particles released during the incomplete combustion of organic matter are carbon monoxide, polyorganic and polyaromatic hydrocarbons such as benzopyrenes fluorine, pyrene, chrysene, benzoanthracene, and benzofluoranthene.[3],[4] These noxious particles cause inflammation in airway and alveoli which leads to irreversible parenchymal destruction such as emphysema and chronic bronchitis. Lung histopathology in COPD patients exposed to biomass fuel smoke had more pigment deposition and fibrosis(bronchial anthracofibrosis) as compared to the cigarette smoker COPD.[5]

In India, still large population, especially women are getting exposed to indoor pollution which causes COPD and other respiratory problems. This study tried to evaluate the strength between indoor pollution and COPD, especially in women.


  Patients and Methods Top


The study was conducted in the Department of Pulmonary Medicine in King George Medical University, Lucknow, Uttar Pradesh. This observational case–control study was approved by the Institutional Ethical Committee.

The study population

Cases

These were patients of nonsmoker COPD with age>45years confirmed by spirometry.

Controls

These were age(>45years), sex-and socioeconomic status class-matched bystanders(friends and relatives) of patients coming to the Outpatient Department(OPD). For each COPD patient, two-matched controls were taken and interviewed at the same time. No non-COPD patient admitted or attending OPDs was taken as control. This was done to avoid a bias described by Berkson.

Sample size

Cases: 164; controls: 328.

Methods

After obtaining the informed and written consent, all patients and controls were interviewed to get the detail of various exposures as follows: passive smoking, indoor pollution, occupational exposure to dust/fumes, the presence of recurrent ear, nose, and throat disease, and a history of respiratory infection in childhood. The history of exposure to various noxious particles such as the type of exposure, frequency, and duration of exposure was taken in detail.

All patients were managed according to the GOLD guideline.

Statistical methods

The data were collected on a predesigned and pretested schedule was entered into the Microsoft Excel® for subsequent analysis. Continuous variables were recorded as mean±standard deviation. The difference between the means of two continuous variables was tested using t-tests. Categorical variables were recorded as frequencies. Associations were studied through the EpiInfo software Epi InfoTM Build 7.2.2.16 (CDC, USA) by calculation of odds ratio(OR) and P value using the Chi-square test with or without Yates' correction, as applicable. Avalue of P <0.05 was considered as statistically significant.


  Results Top


In this study, a total 164patients of COPD who met the inclusion and exclusion criteria and twice the number of age-matched controls(328) were studied. Socioeconomic status of patients was determined by the Kuppuswamy scale.[6] In this study, majority of population belonged to a rural area. The sociodemographic data are given in [Table1].
Table 1: Sociodemographic characteristics of patients of chronic obstructive pulmonary disease and controls

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Out of 164 COPD patients, 148 had one-risk factor exposure, whereas 16patients had two-risk factor exposures. Since majority of our population was from a rural area, indoor pollution in the form of biomass fuel, stove exposure, and wood fire exposure was more common. Indoor pollution exposure was dominantly present in 72patients of total 164 COPD patients(43.9%), whereas in the control group, domestic exposure was in only 64 out of 328 controls(19.5%). [Figure1] shows the distribution of exposure of various risk factors in nonsmoker COPD patients. [Figure2] shows the female predominance in indoor pollution exposure as Indian women, especially in rural areas, use biomass fuel for cooking. In other exposure groups, males are predominant.
Figure 1: Risk factors exposure in chronic obstructive pulmonary disease patients

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Figure 2: Female predominance in indoor pollution exposure as Indian women, especially in rural areas, use biomass fuel for cooking. In other exposure groups, males are predominant

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The various indoor air pollution exposures found in the case of COPD and controls are shown in [Table2]. Common domestic smoke exposures, especially in Indian women are biomass fuel, wood fire, coal, and stoves, etc.,[Figure3]. Women usually get multiple exposures with these noxious particles while cooking.
Table 2: Distribution of various exposures among different classes of socioeconomic status in cases and control groups

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Figure 3: Gender distribution of various indoor air pollutants

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The odds of having biomass fuel smoke exposure among males were 4.25 while in the female it was 4.37 [Table 2]. Overall OR is 3.16. The odds of having other types of indoor pollution such as wood exposure, coal and stove exposure in COPD patients are 2.70, 2.45, and 2.05, respectively, in comparison to the control group. Among the above exposures, biomass fuel smoke, wood smoke exposure, and coal smoking were statistically significant with value of P =0.0001, 0.003, and 0.02, respectively [Table 3].
Table 3: The various indoor air pollution exposures found in case of chronic obstructive pulmonary disease and controls

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The duration of exposure for domestic smoke in our patients is given in [Table4]. The mean duration of exposure for biomass fuel, wood exposure, coal, and stove smoke in cases was 3.44, 3.0, 2.14, and 2.75 h/day while in controls it was 3.31, 4.75, 3.0, 3.0 h/day. Only wood exposure and coal exposure difference was significant in COPD group compared to that of controls(P=0.038 and 0.04). When the years of exposure was analyzed, except stove smoke exposure(P =0.091), all other exposures were statistically significant in COPD patients as compared to controls.
Table 4: Duration of exposure for domestic smoke exposure

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  Discussion Top


Till recently, cigarette smoking was thought to be the major risk factor for COPD, but recent studies have shown nonsmoking factors are also a major risk factor for COPD. In a study done by Mahmood et al., out of 200 confirmed COPD patients, there were 56.5% nonsmokers and 43.5% smokers.[7] In developing countries such as India, coal, wood, and cow dung are major fuels used for cooking. Women and children have the highest amounts of exposures. Hence, biomass fuel smoke exposure is a major cause of COPD in women in developing countries. The biomass smoke acts as noxious particles and induces inflammatory response and tissue damage in airways. In genetically primed individuals, it causes irreversible obstructive airway disease.

In most studies, authors meant biomass fuel exposure as indoor pollution. We have segregated various types of indoor pollution in detail. Biomass fuel exposure is only one of the components of indoor pollution.

In a study by Mahmood et al.,[7] among all nonsmoker COPD, biomass fuel exposure(indoor pollution) was in 53.98% patients, while in the present study, indoor pollution was 43.9%[Figure1]. This difference can be attributed to the different type of population as the majority of this study population belonged to low-socioeconomic status(69.3%) as compared to the study population(35.3%)[Table1].

Hu et al.,[8] in their case–control study, showed OR of 2.44(95% confidence interval[CI], 1.9–3.33) in biomass fuel exposure in developing COPD in comparison to controls, whereas in this study, OR was 3.16[Table3].

Pérez-Padilla et al.[9] in the case–control study on exposure to biomass smoke and chronic airway disease in Mexican women found that OR for wood smoke exposure was 3.9 while in this study crude OR was 2.70, whereas in female population, it was 3.10 which is comparable with the above study.

In India, especially in rural area, women get higher domestic exposure as compared to the male population. Smith et al.[10] studied domestic exposure in women of age>30years in rural areas and showed the relative risk 3.2(95% CI 2.3–4.8) for COPD while Balmes [11] showed relative risk of 1.78(95% CI 1.45–2.18) in the same type of population. June Y T Po took 25 studies in their meta-analysis of indoor pollution, they showed OR of 2.40(95% CI 1.47–3.93) in the female population. While in this study, OR was 5.63[Table3].[12] This wide difference in various studies was due to smoke quality or fuel quality and emitted smoke from those fuels.

Moreira et al. studied smoke from wood combustion in Brazilian female population, they showed that the COPD group had greater exposure in years to wood smoke(P=0.043) than the control group. In this study also numbers of years exposed to wood combustion is statistically significant(P=0.0009)[Table4].[13]

In this study, we found that the long-term biomass fuel exposure and coal smoke exposure in terms of number of years are hazardous in COPD group as compared to the control group(P=0.0001, 0.0009, and 0.0006, respectively). This finding was supported by Pérez-Padilla et al.[9] who found that risk of COPD increased in early age with hours–years of cooking. OR in patients exposed for≥200h years compared with that in nonexposed was 15 for COPD disease and 75 for COPD with chronic airway obstruction.

Smith et al. also studied pediatric age group of<5years in the rural area and showed relative risk for acute lower respiratory disease was 2.3(95% CI 1.9–2.7).[10] This shows that children living in indoor air pollution environment are not safe and in the long term, they are more likely to get COPD.

Limitation in study

This study was not able to estimate the association of COPD with indoor pollution in general population as smokers were excluded from the current study.


  Conclusion Top


Indoor air pollution such as burning of biomass fuel, wood exposure, and coal fuel exposure are associated with COPD in the nontobacco smoker group. Good ventilation and alternative cooking fuels such as liquid petroleum gas may reduce the incidence of COPD in the developing world.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Global Initiative for Chronic Obstructive Lung Disease. GOLD 2018 global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease, 2018 report. November 20, 2017. Available from: https://goldcopd.org/wp-content/uploads/2017/11/GOLD-2018-v6.0-FINAL-revised-20-Nov_WMS.pdf. [Last accessed 2018 Mar 27].  Back to cited text no. 1
    
2.
World Health Organisation. Chronic Obstructive Pulmonary Disease(COPD). World Health Organisation; 2016. Available from: http://www.who.int/mediacentre/factsheets/fs315/en/.[Last accessed on 2017Jun15].  Back to cited text no. 2
    
3.
PrasadR, SinghA, GargR, GiridharGB. Biomass fuel exposure and respiratory diseases in India. Biosci Trends 2012;6:219-28.  Back to cited text no. 3
    
4.
BalakrishnanK, SankarS, PadmavathiR, SmithKR. Respirable particulate levels in rural households of AndhraPradesh, India: Daily concentrations and exposures. JEnviron Stud Policy 2002;5:87-97.  Back to cited text no. 4
    
5.
KimYJ, JungCY, ShinHW, LeeBK. Biomass smoke induced bronchial anthracofibrosis: Presenting features and clinical course. Respir Med 2009;103:757-65.  Back to cited text no. 5
    
6.
KuppuswamyB. Biology and health. In: ParkJE, ParkK, editors. Text Book of Social and Preventive Medicine. 10thed. Jabalpur: Banarsidas Bhanot; 1985. p.63-5.  Back to cited text no. 6
    
7.
MahmoodT, SinghRK, KantS, ShuklaAD, ChandraA, SrivastavaRK. Prevalence and etiological profile of chronic obstructive pulmonary disease in nonsmokers. Lung India 2017;34:122-6.  Back to cited text no. 7
[PUBMED]  [Full text]  
8.
HuG, ZhouY, TianJ, YaoW, LiJ, LiB, etal. Risk of COPD from exposure to biomass smoke: Ametaanalysis. Chest 2010;138:20-31.  Back to cited text no. 8
    
9.
Pérez-PadillaR, RegaladoJ, VedalS, Paré P, ChapelaR, SansoresR, etal. Exposure to biomass smoke and chronic airway disease in Mexican women. Acase-control study. Am J Respir Crit Care Med 1996;154:701-6.  Back to cited text no. 9
    
10.
SmithKR, MehtaS, Maeusezahl-FeuzM. Indoor air pollution room household use of solid fuels. In: Comparative Quantification of Health Risks: Global and Regional Burden of Disease Attributable to Selected Major Risk Factors. Geneva, Switzerland: World Health Organization; 2004. p.1453-93.  Back to cited text no. 10
    
11.
BalmesJR. When smoke gets in your lungs. Proc Am Thorac Soc 2010;7:98-101.  Back to cited text no. 11
    
12.
PoJY, FitzGeraldJM, CarlstenC. Respiratory disease associated with solid biomass fuel exposure in rural women and children: Systematic review and meta-analysis. Thorax 2011;66:232-9.  Back to cited text no. 12
    
13.
MoreiraMA, BarbosaMA, JardimJR, QueirozMC, Inácio LU. Chronic obstructive pulmonary disease in women exposed to wood stove smoke. Rev Assoc Med Bras(1992) 2013;59:607-13.  Back to cited text no. 13
    


    Figures

  [Figure1], [Figure2], [Figure3]
 
 
    Tables

  [Table1], [Table2], [Table 3], [Table4]



 

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