Air pollution and respiratory dysfunction among adolescents: A case–control study from North West India
Vikramjeet Singh1, Varun Kaul2, Rekha Harish3, Nirlep Kaur4, Seema Rai2, Shilpa Bansal2, Sunil Kumar Raina5
1 Consultant Pediatrics, J and K Health Services, Jammu and Kashmir, India
2 Department of Pediatrics, Guru Gobind Singh Medical College Faridkot, Punjab, India
3 Department of Pediatrics, GMC, Jammu, Jammu and Kashmir, India
4 Department of Pharmacology, Institute of Dental Sciences, Sehora, Jammu and Kashmir, India
5 Department of Community Medicine, Dr. Rajendra Prasad Government Medical College, Tanda, Himachal Pradesh, India
|Date of Web Publication||12-Oct-2018|
Source of Support: None, Conflict of Interest: None
Introduction: Children are vulnerable to the effects of air pollution because of immature organ system and immune system. Air pollutants can lead to both upper and lower respiratory tract symptoms.
Methodology: Adolescents in the age group of 10–19 years children from residential areas with established maximal and low pollution levels as reported by State Pollution Control Board were included in the study using age-, sex-, weight-, and height-matched case–control study design. For the assessment of respiratory dysfunction, the values of forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC, and forced expiratory flow (FEF) 25%–75% were included in this study. Odds ratio with 95% confidence interval was calculated to ascertain the strength of association.
Results: The distribution of abnormalities for a restrictive pattern in males in polluted group was 42% as compared to 29% in low polluted group (P = 0.007). The mean values of pulmonary function parameters FVC, FEV1, FEV1/FVC, and FEF 25%–75% (expressed as percentage of predicted values) were compared in two groups, a deficit of approximately 4.5%, 6%, 1.06%, and 3.4% was observed in males versus 4.9%, 6.3%, 2.44%, and 2.4%, respectively for females.
Conclusion: There is a statistically significant difference in the pulmonary functions in the polluted versus less polluted areas with the children being affected in a harmful manner in the former areas.
Keywords: Adolescents, air pollution, North-West India, respiratory dysfunction
|How to cite this article:
Singh V, Kaul V, Harish R, Kaur N, Rai S, Bansal S, Raina SK. Air pollution and respiratory dysfunction among adolescents: A case–control study from North West India. Indian J Allergy Asthma Immunol 2018;32:59-64
|How to cite this URL:
Singh V, Kaul V, Harish R, Kaur N, Rai S, Bansal S, Raina SK. Air pollution and respiratory dysfunction among adolescents: A case–control study from North West India. Indian J Allergy Asthma Immunol [serial online] 2018 [cited 2018 Oct 12];32:59-64. Available from: http://www.ijaai.in/text.asp?2018/32/2/59/243229
Repeated and chronic exposure to air pollutants may lead to long-term cumulative lung damage. Scientific understanding of the spectrum of health effects in children in response to air pollution is constantly increasing and there are numerous reports of adverse health effects from pollution levels previously considered safe., Children living in communities with higher levels of ambient air pollution tend to have lower average lung function, slower rates of lung function growth, and pulmonary reserve volume., A significant association has also been found between maternal exposures to ambient air pollution during pregnancy and fetal growth restriction., Air pollutants can lead to both upper and lower respiratory tract irritant symptoms. Various Volatile Organic Compounds (VOCs) cause multiorgan irritation and damage. The individual or combined effects of air pollutants such as a 10 μg/m3 increase in particulate matter of median aerodynamic size <10 μm (abbreviated as PM10) is associated with an increase of 0.5%–1.5% in daily mortality; a 10%–25% increase in bronchitis or chronic cough and a decline of up to 2% in lung function and lead to various forms of pulmonary obstruction and in some cases death. Effects of air pollution can be either acute or/and chronic. Acute adverse effects are seen in the form of sore throat, cough, runny nose, wheezing, bronchitis, acute exacerbation of asthma, etc., In some studies, lagged pollution effects of up to approximately 5 days have been observed. In long-term effects (exposure > 1 year) increased mortality, changes in lung function, increased hospitalizations, and more health care visits for respiratory and cardiovascular problems were seen. Recently, air pollution has also been implicated in retarding lung function growth in growing healthy children.,,, Lung function is an excellent operative marker of the effects of air pollution in the general population. It is objective and quantitative, an early predictor of cardiorespiratory morbidity and mortality and coherent with experimental data on deposition and accumulation of pollutants in airways and lungs and the resulting systemic inflammation and oxidative stress.,, Pulmonary function tests is a generic term used to indicate a battery of studies or maneuvers that may be performed using standardized equipment. Spirometry is one of these tests, done with the help of spirometer, and the data thus obtained in graphic form is called spirogram. It is a valuable tool for the evaluation of the respiratory system. It is helpful in categorizing illness and defining prognosis.,, The measured values for an individual at any particular point in time are compared with normative values derived from population studies and percent predicted is used to grade the severity; value of less than 80% of the predicted value is usually considered abnormal.,, Various studies have evaluated the effects of specific pollutants (viz PM10, Ozone, and SO2) on lung functions. Nonavailability of hand-held pollution measuring devices, which quantify the pollutant levels, has been the limitation for such studies in our setup. There are some studies in India on this topic, but data from pollution monitoring centers has not been taken for such analysis. Very few studies have been done in the pediatric age group. Hence, this study was done to compare the pulmonary functions of healthy adolescents studying in schools situated in highly polluted areas with those studying in schools of low polluted areas.
The present study was conducted in 10–19-year-old school children at places with established maximal (cases) and low pollution levels (controls) as reported by State Pollution Control Board. The details are as shown in [Table 1].
Inclusion criteria were 10–19 years age asymptomatic children of either sex studying in the school for >3 years. Exclusion criteria consisted of history of acute or persistent respiratory symptoms in the child, history of any illness likely to give rise to alteration in pulmonary functions, for example, empyema, pleural effusion, pulmonary tuberculosis, foreign body removal, lower motor neuron paralysis, for example, Gullian-Barre Syndrome, etc., history of atopy in the child, namely asthma, allergic rhinitis, or atopic dermatitis, underlying congenital anomaly or acquired lesion which could account for recurrent respiratory problems, for example, scoliosis, Potts spine, fracture rib, heart defect, children exposed to domestic fuels (biomass or kerosene) at home, exposure to passive smoke and furry pets at home, child with cleft lip or palate, and facial paralysis or any other alteration that would prevent spirometry from being performed. For enrollment, systematic random sampling was done by choosing all the odd roll numbers in a class. A total of 1350 target sample was selected, out of which only 1328 responded and 22 refused. A total of 1010 were found to be eligible after deducting those with any of the exclusion criteria. Hence, a total of 841 students were analyzed in the study. A total of 417 children from schools in maximal pollution group and 424 children from the low pollution group were thus enrolled. Medical International Research Spirolab II was used. The students underwent a forced spirometry. They were asked to sit comfortably for 5 min and were made to relax. The procedure was explained through self-demonstrations. For the purpose of data collection, three trials were recorded (As recommended by American Thoracic Society and European Respiratory Society). The best of the three trials was taken as the final reading, provided it was reproducible. The readings were taken in sitting posture for all children so as to standardize the procedure. Sufficient time was given between each test so that the individual was comfortable and had no feeling of dizziness. The data were analyzed with the help of computer software Epi-Info version 6.0.1 and SPSS 10.0 (International Business Machines Corporation, Armonk, New York, U.S.) for windows. For analysis purpose, the values of forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC, and forced expiratory flow (FEF) 25%–75% were included in this study. Odds ratio with 95% confidence interval was calculated to ascertain the strength of association. Chi-square test was applied to evaluate statistical significance. P < 0.05 was considered statistically significant unless mentioned otherwise. Confounding factors were dealt with appropriately.
The distribution of pulmonary function abnormalities for FVC in males was 44% and 29% in moderately polluted versus low polluted areas, respectively (P = 0.001) whereas the corresponding values in females were 31.5% and 21.35%, respectively (P = 0.02).
Hsiue et al. also observed that air pollution (resulting from wire reclamation incineration) resulted in an increase in the pulmonary function abnormalities for FVC in 11.9% of polluted group children as compared to 4.1% in low polluted group (P ≤ 0.05). Similarly, Wang et al. observed a significant decrease in FVC in children studying in schools with high pollution levels (15.6% for polluted groups as compared to 65% for low polluted group, P < 0.05). However, these results are not fully comparable due to the difference in study designs including lower age group and small sample size. Langkulsen et al. compared the effect of air pollution on children’s lung function in 10–15 years age group living in areas with different levels of air pollution and observed that children living on roadside with high pollution have around two-fold chances of developing impaired lung function as compared to the children living in low polluted areas (P < 0.01). Because sample was almost of the same age group results were comparable with the present study.
Slower lung function growth regarding FVC in children living/studying in polluted areas assessed over period of time have been observed by several authors., In the present study, 27% of males had pulmonary function abnormalities regarding FEV1 in moderately polluted group as compared to 14% of such males in low polluted group (P = 0.001). The corresponding figures in females were 19% and 13%, respectively (P = 0.04). The trends observed in the present study are similar to previous studies; 16.5% versus 7.2% and 17% versus 3.2%. Peters et al. in their prospective study over 10 years in school children observed that nitrogen dioxide and particulates matter of diameters <2.5 μ (PM2.5) were most strongly associated with lower FEV1 (P < 0.01) comparable with two-fold risk observed in the present study. Children exposed to high pollution have slow lung function growth as compared to those with low pollution levels., Jedrychowski et al. in their prospective study in 1001 preadolescents from different areas of air pollution observed a significant association for slower lung function growth and air pollution. Gauderman et al. in their prospective cohort study also observed a significant proportion of 18-year-old individuals with low FEV1 (<80% of expected) and comparable with present study as 3-year time in school could be assumed as the liver function growth association with air pollution exposure. In the present study, the observed alteration for FEV1% in males was 6.6% in polluted group as compared to 1.9% in low polluted group (P = 0.02). The corresponding values for females were 1.43% and 0.46% (0.36), respectively. Thus, a significant alteration in FEV1% was observed for males only. Most of the studies available in literature are based on three parameters, namely FVC, FEV1, and FEF 25%–75%.,
The pulmonary function abnormalities for FEF 25%–75% in our study in polluted group were 7% and 10.52% for males and females, respectively as compared to 2% and 5.11% in low polluted group (P = 0.04 and 0.05 respectively). There were significant abnormalities in FEF 25%–75% values seen in number of studies between polluted and low polluted population.,,,, The present study is not fully comparable to those mentioned above as they were prospective cohort studies. Their sample size was also larger than the present study. The pattern of airflow limitations can be either obstructive or restrictive. The distribution of abnormalities for restrictive pattern in males in the polluted group was 42% as compared to 29% in low polluted group (P = 0.007). The corresponding figures in case of female were 31.5% and 21.39% (P = 0.02). The distribution of obstructive pattern of abnormality for males was 4.34% in polluted group as compared to 1.94% in low polluted group (P = 0.24). The corresponding values of females were 1.43% and 0.46% respectively (P = 0.36). Although few citations are available in literature regarding FEF 25%–75%, the trends of these observations are similar to some earlier observations made by other authors with values (11.9% vs. 1.1%), (28.4% vs. 1.7%) obstructive and restrictive pattern, respectively. When the mean values of pulmonary function parameters FVC, FEV1, FVC, FEV1%, and FEF 25%–75% (expressed as percentage of predicted values) were compared in two groups, a deficit of approximately 4.5%, 6%, 1.06%, and 3.4% was observed in males. The corresponding deficits in females were 4.9%, 6.3%, 2.44%, and 2.4%, respectively. This was measured as secondary outcome, and no statistical method was applied to these observations. These observations are similar to the observations made in aspects of FEV1 were 3.4%, 3.5%, 6%, 6.38%, FVC were 3.1, 1%, 6.75, and FEF 25%–75% were 5%.
In the present study, the alteration in pulmonary functions were significant in both males and females for all parameters tested except for FEV1% and FEF 25%–75% which were not significantly altered in females (P = 0.36 and 0.05, respectively) may be because of less exposed to pollution or absenteeism from school. Some authors have observed an increased incidence of pulmonary function abnormalities in boys while some have observed an increased incidence of pulmonary function abnormalities in girls, whereas some studies have not observed any relation of gender with pulmonary functions.,
Epidemiologic studies are vulnerable to selection, information, and confounding bias. In the present study, significant alterations in pulmonary functions were observed not only between two groups in the children studying in low polluted areas, incidence of pulmonary function abnormalities was also very high as compared to other studies. The reasons could be indoor and residential air pollution. Indoor air pollution and passive smoking have been implicated in causing lung function defects. Since this study was school based, the residential air pollution can act as confounder. Children studying in these schools come from areas with different levels of air pollution. The bias, intentional, or recall, in answering the questionnaire also cannot be completely ruled out. Since the cross-sectional study was applied, the causal association may not be determined. This work is the beginning of health effect study in children in relation to air pollution. From the results, it could be suggested that living in polluted areas may lead to the chronic adverse effects on respiratory system growth and function in addition over and above the acute health effects as reported by the previous studies.
A statistically significant difference was observed between the pulmonary functions in the polluted versus less polluted areas with the children being affected in a harmful manner in the former areas.
Logistic support by Cipla India by providing a spiroman with a spirometer for the entire duration of the study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.