ENVIRONMENTAL IMPACT ON PHYSIOLOGICAL RESPONSES OF UNDERGROUND COAL MINERS IN THE EASTERN PART OF INDIA.

Coal in India is extracted generally by semi-mechanized and mechanized underground mining methods. The Bord and Pillar (B & P) mining method still continues to be popular where deployment of manual miners is more than that of other mining methods. The study is conducted at haulage based mine of Eastern Coalfields of West Bengal. Underground miners confront with a lot of hazards like extreme hostile environment, awkward working posture, dust, noise as well as low luminosity. It is difficult to delay the onset of fatigue. In order to study the physiological responses of trammers, various parameters like working heart rates, net cardiac cost and relative cardiac cost including recovery heart rate patterns are recorded during their work at site. Workload classification of trammers has been done following various scales of heaviness. The effect of environment on the physiological responses has been observed and suitable recommendations are made. The work tasks are bound to induce musculoskeletal problems and those problems could be better managed through rationalizing the work-rest scheduling.

Maximum aerobic capacity of underground coal miners in India.

Miners fitness test was assessed in terms of determination of maximum aerobic capacity by an indirect method following a standard step test protocol before going down to mine by taking into consideration of heart rates (Telemetric recording) and oxygen consumption of the subjects (Oxylog-II) during exercise at different working rates. Maximal heart rate was derived as 220-age. Coal miners reported a maximum aerobic capacity within a range of 35-38.3 mL/kg/min. It also revealed that oldest miners (50-59 yrs) had a lowest maximal oxygen uptake (34.2 ± 3.38 mL/kg/min) compared to (42.4 ± 2.03 mL/kg/min) compared to (42.4 ± 2.03 mL/kg/min) the youngest group (20-29 yrs). It was found to be negatively correlated with age (r = -0.55 and -0.33 for younger and older groups respectively) and directly associated with the body weight of the subjects (r = 0.57 - 0.68, P ≤ 0.001). Carriers showed maximum cardio respiratory capacity compared to other miners. Indian miners VO(2 max) was found to be lower both compared to their abroad mining counterparts and various other non-mining occupational working groups in India.

A comparison of cardiac strain among drillers of two different age groups in underground manual coal mines in India.

Cardiac strain was evaluated in terms of working heart rate (WHR), relative cardiac cost (RCC), net cardiac cost (NCC) and other recovery indices among six younger (mean age 34.2 +/- 2.7 yr) and sixteen older (mean age 48.9 +/- 5.4 yr) drillers working in a manual underground coal mine over two spells of work. The mean WHR was within the range of 117-132 beats / min with corresponding mean relative cardiac cost between 44-48% of heart rate reserve for the younger group and 53-55% for their older counterparts. The mean NCC was above 50 beats/min for both age groups. It was seen that the workers surpassed the recommended limits of cardiac strain indices. The intensity of workload indicates the job to be "heavy" to "extremely heavy" in accordance with the heaviness scales based on WHR, NCC and recovery heart rates. Heat stress prevailing in the workplace in terms of effective temperature (ET) and wet bulb globe temperature (WBGT), was above the recommended limits as per the guidelines proposed by WHO and ACGIH. High physiological demands of the job which requires predominate static muscular exertions coupled with high heat stress were found to hinder the recovery process and may prove deleterious particularly for the older workers. Therefore, in the present context, the need of ergonomic interventions for job organization and quick reparation of environmental condition are strongly indicted.

A comparison of physiological strain of carriers in underground manual coal mines in India.

Thirty-nine healthy carriers (23-57 years of age) were investigated in underground manual coal mines in West Bengal, India during two different work spells of a single work shift. We compared physiological strain of workers <40 and > or =40 years of age. For both groups, mean heart rate was 124-133 beats/min, with a mean corresponding relative cardiac cost of 50-66%. Maximum aerobic capacities were estimated indirectly, following a standard step test protocol. Average oxygen consumption was 1.07-1.1 l/min, with an energy expenditure of 5.35-5.5 kcal/min among both age groups. Acceptable levels of physiological strain were well encroached, and older workers faced the maximum burden. The tasks studied were heavy to very heavy in nature. The weight of load carriage at a spontaneously chosen speed and the prevailing environmental conditions merit serious attention. There is extreme need of ergonomic interventions in reducing the postural load and musculoskeletal discomforts in this population.

A comparative study of physiological strain of underground coal miners in India.

Ninety-eight healthy underground coal miners aged between 23-58 years were studied during their activity period. Physiological strain of different category of miners in terms of heart rate was monitored continuously with heart rate monitor that revealed the tasks as heavy to very heavy for them. Oxygen consumption was measured directly by using oxylog-2 machine that corresponded to metabolic costs for different activities ranging from 4.96 kcal/min to 5.47 kcal/min. The mean relative aerobic strain varied from 47.4%-56.8%--depicting acceptable level of physical strain was well encroached by the miners who irrespective of ages and categories showed poor recovery responses. This entails that miners are exerting themselves beyond their capacities where inevitably older workforce face the maximum burden.

A study of the workload of underground trammers in the Ranigang coal field area of West Bengal, India.

Thirty healthy trammers were examined in underground haulage mines during their normal activity. Physiological strain in terms of heart rate (HR) varied between 101.6 and 104.7 beats/min with mean net cardiac cost of 33.06 and 34.06 beats/min for younger and older groups respectively. The average relative cardiac cost was lower for younger subjects than for older ones. Oxygen consumption (VO2) was measured with an Oxylog-II machine (UK); subsequently values were estimated. Maximum aerobic capacity was estimated with an indirect method following a standard step test protocol. The responses revealed that the average VO2 during the activity was 0.75 and 0.8 L/min, which corresponded to energy expenditure (EE) of 3.8 and 3.97 Kcal/min for younger and older subjects respectively. The workload in terms of HR and EE was moderate, whereas the aerobic strain experienced by aged workers was above the acceptable level.

Cardiovascular load assessment of coal mine shovelers in west Bengal, India: a comparison between middle age groups.

Cardiovascular load of underground shovelers was assessed in terms of heart rate changes at work in haulage coalmines. Twenty underground shovelers of two different age groups (those of age 31-39 and those of age 40-49) served as subjects. Working heart rate was significantly higher (p < 0.01) in the older group (138.2 beats/min) than in the younger group (130.4 beats/min). Though the net cardiac cost did not differ significantly between the groups (64.8 beats/min and 69.4 beats/min in younger and older groups, respectively), difference in the relative cardiac cost (54.17% and 64.86% in younger and older groups, respectively) proved to be highly significant (p < 0.001). The heart rate up to the third minute of recovery showed significant differences between the groups (p < 0.01). While analysis of physiological responses indicated that the task was very strenuous irrespective of age, cardiac strain was found to be more excessive in the older subjects if continued. The arduous nature of the working environment in the coalfaces was also reported.