Health Status of the Coal Mine Workers in an Open-cast Mine of Eastern India

INTRODUCTION WITH OBJECTIVES

The four major coal types ranked in order of increasing heat value are lignite, subbituminous, bituminous, and anthracite. The inorganic portion of coal can range from a few percent to >50% (by weight) and is composed of phyllosilicates (kaolinite, illite, etc.), quartz, carbonates, sulfides, sulfates, and other minerals. Apart from dust exposure, confrontation with metals during work is a hazard in coal mining. Aluminum and iron are the main metals in coal. Arsenic, nickel, zinc, cadmium, cobalt, and copper are trace metals that represent only a very small fraction of the mineral matter.¹

Coal mining in India has a long history of commercial exploitation covering nearly 220 years, starting in 1774 in the Raniganj Coalfield along the Western bank of river Damodar. However, for about a century, the growth of coal mining in India remained sluggish. Later on, from 1853, it again gained momentum through introduction of steam locomotives industries. As of 2011, India had 285 billion tonnes of resources. In 2010–11, the production of coal was 532.69 million tonnes. The production of lignite was 37.73 million tonnes in 2010–11. In 2011, India ranked third in world coal production.²

Coal remains a major energy resource worldwide. However, coal mining causes environmental problems such as acid mine drainage, whereas the inhaled coal particles at the workplace may lead to the development of coal workers’ pneumoconiosis (CWP).^3,4 Typically, coal workers’ pneumoconiosis takes many years to develop and be manifested that requires surveillance for a long duration. Further, once initiated, the disease is progressive in nature, often leading to lung function impairment, disability, and premature death.

Apart from CWP, coal mining can also increase the risk of developing asthma and chronic obstructive pulmonary disease, such as emphysema and chronic bronchitis.^5-7 It is suggested that coal dust stimulates the recruitment of neutrophils to the lungs, and both these neutrophils and resident alveolar macrophages show evidence of activation, secreting free radicals and proteolytic enzymes, and plausible mediators of tissue injury in emphysema.^8-10

Extensive mining, including coal mining, is undertaken in different parts of India. Nowadays, as far as coal mining is concerned, more and more open-cast mines are emerging in contrast to older underground mines. This shift is friendly to workers’ health. However, considering the environmental– occupational hazards inherently involved, regular and periodic monitoring of environmental conditions and the health status of the workers is always necessary. Under this background, the present study was undertaken with the aim of studying the coal mining as well as coal dust-related health effects in the open-cast mining workers.

MATERIAL AND METHODS

An occupational health study was conducted involving different mining areas of the concerned mining project during 2019–2020. This cross-sectional study was undertaken among the exposed workers mainly from active mining and crushing activity. A representative sample of workers working in such occupations is included in this study. Initially, the aim of the study was explained to the workers; informed consent was obtained after which they were enrolled for this study. Every individual subject was interviewed with a pre-designed questionnaire to collect information in relation to the personal, occupational, and morbidity details of the workers. Informed consent was obtained from each study participant. This study covered about 250 participants from the mining project. These workers were randomly selected from the total exposed workforce (workers in active mining and crushing activity). This was followed by clinical examination and spirometry of each subject.

Comprehensive anthropometric characteristics of the subjects were measured. The nutritional status of the workers was also estimated by standard anthropometry¹¹ and body composition using standard anthropometric equations.^12-14 The subjects were classified for their nutritional status based on body mass index.¹⁵

RESULTS

This study covered 250 workers. Although the majority of subjects were actively involved in mining activity, about 32% of subjects of this study were enrolled by allied staff to have a complete and comprehensive understanding of the occupational health condition. However, these allied workers were spending all of their duty time in the same work atmosphere as active mining workers. Moreover, they included coal-carrying heavy truck drivers as well as crusher employees who had ample exposure to coal dust during their jobs.

The mean age of the workers was 29.68 ± 7.10 years. Most of the workers were between the 25- and 34-year age groups. The mean age of allied staff was slightly lower than that of miners. About 80% of workers were married. As far as education is concerned, the majority (66%) had a middle school education. Only about 8% of subjects had a graduate level or higher education. The mean height of the study subjects was 163.94 ± 5.79 cm, and the mean weight was 61.23 ± 10.63 kg. The mean height was slightly higher in allied staff, whereas the mean weight was considerably higher. This may be the result of a sedentary lifestyle and relative lack of exercise. So far, as personal habits are concerned, about 76% of subjects were nonsmokers and about 24% were smokers. Tobacco chewing habit was present in 58% of subjects, and occasional alcohol intake history was found in about 37% of workers. The mean job experience was 5.53 ± 5.02 years. About 62% of workers had job experience of <5 years and about 38% of workers had experience of more than five years. The mean job experience was a little lower in the allied employee group than the miner’s group.

The most common symptom complained by study subjects was musculoskeletal pain (16.8%) [Figure 1]. Other complaints were cough, difficulty in breathing, chest pain, and soreness of mouth. Some subjects also experienced headaches, sleep disturbances, weakness, and tremors in their fingers. The mean systolic and diastolic blood pressure of study subjects was 124.84 ± 14.78 and 77.28 ± 11.27 mm of mercury, respectively. About 10% of subjects had systolic blood pressure >140 as well as diastolic blood pressure >90 mm of mercury. About 5% of workers had only higher systolic blood pressure, and 4% had only higher diastolic blood pressure [Table 1].

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Figure 1:

Distribution of symptoms of the study participants.

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As far as the pulmonary function status of study subjects is concerned, about 7% of subjects had a restrictive type of abnormality (FVC/PFVC <80%). Obstructive type of abnormality was also present in a similar number of subjects. A good number of subjects (17.6%) had FEV_1% values between 70% and 80%. The mean FVC values were significantly lower among the subjects who were 45 years or more of age. The difference was more prominent among the miners in comparison to the supervisory staff. Such a significant difference in FVC values was not observed when compared between higher and lower job experience groups. A significant difference was also observed when compared in relation to the smoking habits of the subjects. A similar trend was not observed in the case of FEV₁ values. No significant difference was observed between subjects of <45 years and the rest of the workers. This trend was similar in miners and supervisory staff. No significant difference in FEV₁ values was observed when compared in relation to the job experience and smoking habits of the study subjects. The mean PEFR values were significantly lower among the subjects aged 45 years or above. The difference was more prominent among the miners in comparison to the supervisory staff. Such a significant difference in PEFR values was not observed when compared between higher and lower job experience groups. No significant difference was observed when compared to the smoking habits of the subjects [Table 2].

A total of 30 personal samplers were placed in three different working areas of the open-cast mine. Concentrations (mean ± SD) of respirable dust in the mining section were 3.8 ± 1.1 mg/m³, 2.5 ± 0.21 mg/m³ in the crusher section, and 2.0 ± 0.4 mg/m³ in the loading section. The levels were found to be relatively higher in the mining section than in the other process units [Table 3].

DISCUSSION

The most common symptom complained about by study subjects in this present study was musculoskeletal pain (16.8%). A report published by Sharma et al. indicated the prevalence of musculoskeletal disorders among general people to be 7.08% in Delhi, 9.53% in Jodhpur, and 11.52% in Dibrugarh.¹⁹

Among the miners, the higher prevalence may be due to workload. Other complaints were cough, difficulty in breathing, chest pain, and soreness of mouth. Some subjects also experienced headaches, sleep disturbances, weakness, and tremors in their fingers. Among the miners, 6.4% were hypertensive in our study, which is almost similar to the findings of the study conducted by Rajashekar et al., where 6.38% of the miners were hypertensive.¹⁹ As far as the pulmonary function status of the study subjects is concerned, about 7% of subjects had the restrictive type of abnormality (FVC/PFVC <80%) in our study. Obstructive type of abnormality was also present in a similar number of subjects. A good number of subjects (17.6%) had FEV_1% values between 70% and 80%.

The mean FVC values were significantly lower among the subjects aged 45 years or above. Such a significant difference in FVC values was not observed when compared between higher and lower job experience, but a significant difference was observed when compared to the smoking habit of the subjects. This result is similar to the findings of two other studies carried out in Southern India²⁰ and Western part of India.²¹ Similar trend was not observed in the case of FEV₁ values. The mean PEFR values were significantly lower among the subjects aged 45 years or above. Such a significant difference in PEFR values was not observed when compared between higher and lower job experience groups. In this respect, our study results are in contrast with the findings of Gupta et al.,²² which showed a reduction in PEFR due to dust exposure.

CONCLUSION

Our study depicts the working conditions and morbidities of workers working in surface mining operations. On the basis of the findings, considering the environmental and occupational hazards involved, our study recommends regular and periodic monitoring of environmental conditions and the health status of the workers involved in all such activities.