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Indian Journal of Community Medicine

A Comparative Study of Air Pollution-Related Morbidity Among Exposed Population of Delhi

Author(s): A Sagar, M Bhattacharya, Vinod Joon

Vol. 32, No. 4 (2007-10 - 2007-12)

ISSN No. 0970-0218

A Sagar, M Bhattacharya1, Vinod Joon1

Abstract

Background: Vehicular pollution is increasing in Indian cities, which may lead to increased number of patients with diseases related to air pollution. Present study was undertaken to assess the pattern of morbidity in two areas of Delhi, one highly polluted area (HPA) and the other low polluted area (LPA). Materials and Methods: Subjects were interviewed regarding socioeconomic status and exposure history. Symptoms during the last month were recorded in a questionnaire and weight, height and peak expiratory flow rate (PEFR) were measured. Air pollution data were obtained from the monitoring stations of Central Pollution Control Board (CPCB). Results: A total of 640 subjects participated in the study. Majority of the patients in both the areas were educated till primary but 24% in HPA and 13% in LPA were graduates. Current levels of all pollutants (except SO2 and NOx) were above the safety levels prescribed by CPCB in both the areas, but the values were much higher in HPA. The values of PEFR amongst study population were more compromised in HPA. The difference in mean PEFR values among the populations in LPA and HPA were found to be statistically significant (P < 0.05). The mean number of symptoms experienced by subjects of HPA was more as compared to LPA (P < 0.05). Frequency of occurrence of symptoms varied with duration of stay in the study area. Children were affected more than the adults. Conclusion: Air pollution has a deleterious effect on various systems of the body.

Keywords: Air pollution, exposure, health effects, peak expiratory flow rate, vehicular emissions

Air quality is deteriorating especially in metropolitan cities, mainly due to vehicular emissions. There is good evidence that the health of 900 million urban people over the world is deteriorating daily because of high levels of ambient air pollutants.1 The toxicology of air pollution is exceedingly complex as there are different types of pollutants affecting individual differently.2

The pollutants in air namely SO2, NOx and suspended particulate matter (SPM) damage the human respiratory and cardio respiratory systems in various ways. The elderly, children, smokers and those with chronic respiratory diseases are most vulnerable.3 It has been reported that high levels of pollution affect mental and emotional health too. Amongst the symptoms, feeling of fatigue, exhaustion, low mood, nervousness, irritation of eyes and stomach aches have shown a significant association with air quality. Inhalation of fumes is associated with recurrent colds, chronic bronchitis and hyperactive airways.4 Elevated lead levels in children have been associated with impaired neurological development as measured by lowered IQ, poor school performance and behavioural difficulties.3

Environmentalists claim that living in an Indian metropolitan city is like smoking 10-20 cigarettes every day. More than 40,000 people die pre-maturely every year because of air pollution, says a World Bank report, of which Delhi’s share is the highest (19%).5 The estimates of disease burden due to urban air pollution are based on the impact of air pollution on mortality. The impact of air pollution on morbidity could not be included in the calculations due to lack of reliable epidemiological data. Few studies have been conducted on the health effects of air pollution in the general population of Delhi. This study is an effort to identify the adverse health impacts due to air pollution on communities residing in areas of high and low ambient pollution levels.

Materials and Methods

This descriptive study was carried out in Delhi, the capital of India. The study areas were taken up randomly from among the areas already identified by the central pollution control board. Daryaganj was identified as highly polluted area (HPA) and Gazipur as low polluted area (LPA). The mean level of pollutants during the previous 1 year was recorded. Two population groups, one from HPA and other from LPA were selected for this study.

A sample of 320 people each was taken up from both LPA and HPA. The sample size was based on the prevalence of symptoms and signs in the studies done earlier, which had found the frequency of mucosal irritation as 39.7% and eye symptoms as 26.9%6 with 10% error. Inclusion criteria for the study was that the person should be living and working in the selected areas for more than 6 months, be below 45 years (to rule out respiratory symptoms associated with old age) and be a non-smoker. The study population was disaggregated into four age groups. The age groups were: 0-5 years, 6-13 years, 14-22 years and 23-45 years, with a sample size of 80 subjects in each age group. Males outnumbered females in both the areas. In HPA, 78% and in LPA, 75% subjects were males.

A pre-coded structured interview schedule was prepared to collect the data. Past history of relevant illness was obtained from the medical records of individuals. Medical examination and certain measurements like weight, height, blood pressure and peak expiratory flow rate (PEFR) were carried out on the spot for each study subject. The levels of pollutants namely SPM [respirable suspended particulate matter (RSPM) and total suspended particulate matter (TSPM)], NO2, SO2 and lead as measured by CPCB were obtained by the investigators. The adverse health effects of pollutants were based on the list of symptoms prepared by the Society for Environment and Health.7 The data were analysed with SPSS and appropriate statistical tests like chi-square test, odds ratio and standard error of mean were used.

Results

The mean values of all pollutants (except SO2 and NO2) exceeded the recommended National Ambient Air Quality Standards (NAAQS) prescribed for residential areas in both Daryaganj and Gazipur, but the values were much lower in Gazipur (LPA).8 The levels of TSPM, RSPM and lead were much above the safety limits prescribed for residential areas by the Central Pollution Control Board for both the study areas.9 The TSPM levels were 683 and 235 μg/m3 for HPA and LPA, respectively.

Fifty-two percent of people in HPA and 47.2% of people in LPA had 3-5 years of stay in their respective areas, and 32.2% of subjects of HPA and 44% of subjects of LPA have been living in that area for nearly 2 years.

As shown in Table 1, majority of subjects in both HPA and LPA were educated till primary. The percentage of graduates was more in HPA than in LPA. In HPA, 84.4% and in LPA, 79.4% of the subjects had knowledge about air pollution as a hazard to health.

Table 2 shows that the values of PEFR were less in HPA as compared to LPA. The PEFR is the indicator of lung function, which is affected as a result of exposure to air pollution.

When the differences in mean number of symptoms experienced by the individuals of HPA and LPA were compared, it was found that the symptoms were more likely to occur in HPA population than in the subjects residing in the LPA. Table 3 shows that higher percentage of subjects of HPA suffered from different symptoms like irritation of nose and eyes, watering of eyes and nose, respiratory infections, breathlessness, ringing in ears and headaches. When the differences between various symptoms experienced by the subjects from HPA and LPA areas were compared, it was found that the symptoms were statistically significant except for a few symptoms like febrile conditions and common cold.

The individual symptoms were analyzed for different age groups and it was observed that the subjects residing in HPA, irrespective of age were likely to have 1.7 to 3.37 times more chances of suffering with the symptoms related to pollution, compared to the subjects residing in LPA. Further, when we compared the symptoms among different age groups, it was found that the age group 14-22 years had the lowest probability of occurrence of various symptoms amongst all the age groups, while the age group 6-13 years had the highest chance of developing various symptoms.

Table 1: Educational status of the study subjects

Educational
status
High pollution
area, No. (%)
Low pollution
area, No. (%)
Total,
No. (%)
Illiterate 24 (7.5) 35 (10.9) 59 (9.2)
Primary 110 (34.3) 108 (33.7) 218 (34.0)
Middle 47 (14.6) 49 (15.3) 96 (15)
Matric 22 (6.8) 35 (10.9) 57 (8.9)
Senior
Secondary
44 (3.7) 52 (16.2) 96 (15)
Graduate 73 (23.1) 41 (13.0) 114 (17.9)
Total 320 320 640

P = 0.01

Table 2: Mean peak expiratory flow rates by duration of exposure

Duration of stay High pollution area Low pollution area
Mean S.D. Total Mean S.D. Total
Up to 2 years 231.9 150.8 103 281.7 157.4 141
3-5 years 414.4 147.3 165 507.6 138.7 151
More than 5 years 527.3 57.2 52 590.4 51.4 28

P < 0.05

Table 3: Symptoms during previous 1 year

Symptoms High pollution area, No. (%) Low pollution area, No. (%) P-value
Burning eyes 124 (38.8) 57 (17.8) <0.001
Irritation of eyes 111 (34.7) 53 (16.6) <0.001
Irritation of Nose 134 (41.9) 54 (16.9) <0.001
Irritation of throat 136 (42.5) 50 (15.6) <0.001
Watering of eyes 125 (39.1) 66 (20.6) <0.001
Watering of nose 170 (53.1) 130 (40.6) <0.001
Respiratory infection 86 (26.9) 36 (11.3) <0.001
Black sputum 45 (14.1) 31 (9.7) 0.08
Cough 220 (68.8) 212 (66.3) 0.4
Breathlessness 112 (35) 48 (15) <0.001
Chest pain 40 (12.5) 23 (7.2) <0.02
Sneezing 168 (52.5) 135 (42.2) 0.008
Common cold 158 (49.4) 113 (35.3) 0.0003
Febrile condition 11 (3.4) 14 (4.4) 0.5
Suffocation 17 (5.3) 9 (2.8) 0.1
Ringing in ears 80 (25) 38 (11.9) 0.00001
Nausea 11 (3.4) 14 (4.4) 0.5
Headache 142 (44.4) 98 (30.6) 0.0003
Vomiting 45 (14.1) 98 (30.6) <0.001
Total 320 320  

Discussion

According to the World Health Report 2002, analyses based on particulate matter estimates report that ambient air pollution causes about 5% of trachea, bronchus and lung cancer, 2% of cardio-respiratory mortality and about 1% of respiratory infections mortality globally. This amounts to about 1.4% (0.8 million) deaths and 0.8% (7.9 million) of disability-adjusted life years. The adverse effects of air pollution are more pronounced in developing countries.10 The problem of air pollution is increasing at an alarming rate in Delhi. It is India’s most polluted metropolitan city with 70% air pollution of Delhi being caused by vehicles only. This has resulted in higher air pollution-related morbidity among its inhabitants.

The study area in Daryaganj is a highly congested area with heavy traffic density and frequent traffic jams, resulting in build up of air pollutants in that area. This ultimately leads to more exposure to people residing and working in that area. Gazipur on the other hand, is a rural area situated on the outskirts of Delhi with less traffic density and consequently less exposure of its inhabitants.

In the present study, mean levels of pollutant in the study areas were almost comparable to the study done by Kamat and others.11,12 In air quality studies, total aerosol in air is measured as TSPM. Course particles are not useful except that it reflects the perception of haze in air and results in diminished visibility. RSPM is the most important fraction from health point of view.

Total exposure of an individual to pollutants is determined by the concentration of pollutants and the duration of exposure. The exposure levels in the study population were measured by the duration of stay of subjects in the study area as up to 2 years, 3-5 years and above 5 years. Sixty-eight percent of the people of HPA and 56% of LPA were staying in the area for more than 3 years. The prevalence of airborne diseases was more in HPA as compared to LPA. This could be due to high levels of air pollutants in their environment specially the RSPM, as these particulates tend to deposit in alveoli and slow down the exchange of oxygen with carbon dioxide in the blood, causing shortness of breath. The number of symptoms observed in this study had more frequency of occurrence in HPA than LPA. The symptoms also vary with different duration of exposure. The findings reported in this study and others regarding respiratory morbidity, lung function and urban air pollutant levels are similar. According to the Health Care Institute of India, there is an alarming rise in number of patients in Delhi hospitals with respiratory problems.13 A study from Cochin also reported higher prevalence of respiratory symptoms.14

A study conducted by All India Institute of Medical Sciences and Central Pollution Control Board in Delhi showed that exposure to higher levels of particulate matter contributed to respiratory morbidity. It indicated that the most common symptoms related to air pollution were irritation of eyes (44%), cough (28.8%), pharyngitis (16.8%), dyspnea (16%) and nausea (10%).15 A similar study in Bombay found the prevalence of symptoms and signs of disease to be around 22.2%.11

In the present study, the PEFR values were found to be much lower than Clement Clark’s Standard. 83.8% of the subjects of HPA were having PEFR values less than normal as compared to 44.1% of the subjects of LPA. Person with less duration of exposure were found to have more compromised PEFR as compared to those with more exposure, since it was observed that as duration increases the acute symptoms subside. Thus, chronic inhalation of air in Delhi caused decline in lung function in a significant percentage of inhabitants of the city. Kumar et al. reported similar findings where the lung functions such as forced expiratory volume, forced vital capacity and peak expiratory volume (PEV) were found to be much lower than normal.15 In a similar study by Kumar et al., the increased risk of having chronic respiratory symptoms was 1.5 (95% CI = 1.2, 1.8; P < 0.00) and that of spirometric ventilatory defects was 2.4 (95% CI = 2.0, 2.9; P < 0.001) in the study town compared with the reference population, even after controlling for the effects of age, gender, education, occupation, income, ever smoking, passive smoking, type of cooking fuel and migration.16

In a similar study conducted by Chitranjan Cancer Research Institute, Kolkata on 1310 individuals from Kolkata and 200 from rural West Bengal, symptoms related to problems in the upper respiratory tract were found in 47.8% of urban people in contrast to 35% of rural controls. Respiratory symptoms were most frequent during winter when the pollution level of the city with respect to respirable particulate matter was the highest. The percentage of individuals with impaired lung function (47%) correlated well with the frequency of lower respiratory symptoms (47.8%) in urban people.17 In another study that compared the ventilatory functions of two groups of school children of Kolkata, one within CMA (study) and another in an area with better ambient air quality, the observations were indicative of a statistically significant impairment of lung functions (PEFR) in the study group exposed to higher concentration of pollutants in the ambient air.18

In the present study, asthma was observed in 23% of patients in HPA compared to 9% in LPA. Allergy and dermatitis was also more in HPA (15.9%) than in LPA (4.7%) population. Thus, the present study is comparable to the studies done earlier by Joshi, in which it was found that lung function was lower in more polluted city zone. For morbidity, the urban area with high levels of pollution was the worst, the medium areas slightly better and the low areas best. The study concluded that most of the health effects observed could be attributed to multiple pollutants.4,7 All these findings both from the present and past studies warrant long-term perspective studies in view of the possible risk of developing obstructive lung diseases.

References

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National Institute of Health and Family Welfare, Delhi, and
(1)Department of CHA, National Institute of Health and Family Welfare, Delhi, India

Correspondence to:
Prof. M. Bhattacharya,
Department of CHA, National Institute of Health and Family Welfare, New Mehrauli Road, Munirka, New Delhi – 110 067, India.
E-mail: cha_nihfw(at)yahoo.co.in
Received: 28.04.06
Accepted: 15.10.07

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