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ORIGINAL ARTICLE
Year : 2011  |  Volume : 15  |  Issue : 3  |  Page : 120-126
 

Cardiac strain of confectionery worker in relation to heat exposure during regular work shift


1 Department of Physiology, Himachal Dental College, Sundernagar, Himachal Pradesh; Foundation for Occupational Health Reform and Developmental Research, Kolkata, West Bengal, India
2 Foundation for Occupational Health Reform and Developmental Research, Kolkata, West Bengal, India
3 Universal College of Medical Sciences, Paklihawa Campus, Bhairahawa, Nepal

Date of Web Publication24-Feb-2012

Correspondence Address:
Rajib Biswas
Himachal Dental College, Sundernagar - 175 002, Dist- Mandi, Himachal Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0019-5278.93202

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  Abstract 

Context: In India, a wide variety of occupations are performed in adverse indoor working environment. Work physiological studies in these jobs are scanty as compared to investigations done on more arduous outdoor occupations. Aims and Objectives: Physiological strain of workers engaged in sweet making activities was assessed in terms of cardiac strain indices in relation to heat stress. Setting and Design: 33 full-time workers from eastern India were compared for cardiac strain profile obtained during summer and winter during their regular work shift. A comparison was also done in between younger (n=12) and older (n=16) subjects. Materials and Methods : Working heart rate (WHR) was recorded continuously during work. The pulse deceleration index (PDI) was obtained from recovery heart rate (RHR). Net cardiac cost (NCC) and relative cardiac cost (RCC) were the main indices used to evaluate physical strain. Thermal stress assessed from wet bulb globe temperature (WBGT). Statistical Analysis: Students' t-test and Wilcoxon signed rank paired tests were used for comparing physiological responses. Values were considered significant when P < 0.05. Results: Work load was significantly higher in summer for all workers. RCC of younger workers in winter and summer ranged between 18% and 26%. This was significantly lower as compared to the RCC of older workers which was 27% in winter and 30% in summer. The physiological workload appeared to be moderate in nature. The WBGT index was above the recommended range in summer for both the groups. Older workers showed a no recovery pattern in terms of recovery pulse that indicated toward a cumulative stress which may be attributed to a combined effect of heat and work in summer and extra amount of work performed in winter season. Conclusion: The physical workload is aggravated with various ergonomic stressors present in the work place. An ergonomic intervention has been indicated as further scope of this study.


Keywords: Heat stress, physiological strain, relative cardiac cost Confectionary work, working heart rate


How to cite this article:
Biswas R, Samanta A, Saha P. Cardiac strain of confectionery worker in relation to heat exposure during regular work shift. Indian J Occup Environ Med 2011;15:120-6

How to cite this URL:
Biswas R, Samanta A, Saha P. Cardiac strain of confectionery worker in relation to heat exposure during regular work shift. Indian J Occup Environ Med [serial online] 2011 [cited 2019 Jul 20];15:120-6. Available from: http://www.ijoem.com/text.asp?2011/15/3/120/93202



  Introduction Top


The vast socio-economic and cultural diversity of Indian Nation has contributed to its wide variety of traditional occupations. A majority of these occupations engage a large number of unorganized sector workforce and involve manual labor. In eastern part of India, in the state of West Bengal, the occupation of sweet making (confectionery work) has developed over centuries. In Bengal, sweets are fondly eaten throughout the year in all occasions. The huge demand of sweet has therefore become an integral part of Bengali life and culture which calls for its extensive production. The sweet making business or the confectionery work, as a result, has evolved as a major small-scale unorganized sector in the state.

In Indian context, a majority of the work physiological studies have focused on jobs that are characteristically dynamic and arduous in nature and performed outdoor. In the last few decades, many such studies have been conducted on determination of physical workload and heat exposure on various occupations, such as stone cutting, [1] unskilled building construction jobs, [2] inland fishing, [3],[4],[5] mining, [6],[7] agriculture [8],[9] work.

In contrast, there are still many occupations which are conducted indoors in adverse work environment with simultaneous exposure to heat. Furthermore, studies reporting on the effect of heat exposure on cardiac and energetic strain in moderately sedentary jobs with repetitive static efforts are scanty. Chronic exposure to heat in work place may result in the failure of homoeothermic control resulting in heat exhaustion and heat stroke. Accordingly, occupational heat exposure standards have been defined to prevent such conditions. [10] While the metabolic heat production parallels the cardiac work load in dynamic work, cardiac stress is often more expressed in static muscular efforts presenting with simultaneous exposure to ergonomic stressors and heat. [11],[12],[13]

The confectionery or sweet making represents one such occupation which is still unexplored from work physiological and ergonomic viewpoint. In this context, the present study aims for evaluating the physical work stress involved in this occupation.

In accordance, physiological work stress is assessed in terms of certain cardiac strain indices in young and older workers during summer and winter. The study intends to focus on the seasonal variations in physiological response of both the groups respect to their activity and ambient temperature during work shift in both the seasons.


  Materials and Methods Top


A total of 33 subjects were selected from 8 different shops of Kolkata, eastern India. The shops were matched for their total number of workers, daily production, workers' salary, size of kitchen area, and work methods. All workshops were located on the ground floor. Two criteria were used for subject selection: full-time involvement in the profession with a minimum work experience of 5 years and no current diagnosed illness. All the workers were married and were living away from their family.

Prior to the study, the subjects were explained about the design of the study and the extent of their involvement. Except two subjects, all showed their willingness to comply with the protocol of the study. Three subjects were unavailable for the seasonal comparison.

Each subject was examined for three working days of a single week in both summer (May - June) and winter (Dec - Jan). In both the seasons, the study was conducted in the morning between 6.00 and 15 .00 hrs. It ensured that the subjects were regularly involved in their job for at least 2 weeks before the study. Regardless the season, the tasks performed by the workers of all the shops were similar in nature and were done manually. During the entire shift, the workers performed different tasks of sweet production which are repeated in a single work shift. The description of these activities and their duration and frequencies are presented in [Table 1]. The total time required to perform these works is termed as the productive period. In addition, the workers were also engaged in non-specific activities like milk weighing, utensil cleaning, milk pouring spreading fried sweets in syrup, etc. Rest pauses include voluntary rest pauses when the workers took breakfast or meals or a few minutes rest.
Table 1: Description of different tasks in sweet making

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The subject's ages ranged between 26 and 55 years. They were classified into two age groups: younger group (YG) having below 40 years of age (n = 12) and older group (OG) having ages between 40 and above (n =16).

Resting heart rate (RHR) was obtained in a seated position after a rest period of ≥30 minutes at a comfortable room temperature in the morning before the beginning of work. The maximum heart rate (MHR) was considered to be 220 less the age of the subjects in years [14] and heart rate reserve (HRR) was obtained as the difference between MHR and RHR.

Heart rate during work and recovery was the principal physiological parameter measured. Working heart rate (WHR) was monitored by a telemetric heart rate monitor (PE 3000, Polar Electro 3000 Finland). Monitoring was done continuously for 90 min in three phases; in between 6.00 and 9.00 hrs, 9.00 and 12.00 hrs, and 12.00 and 15.00 hrs. In all three phases, heart rates were recorded at every 1 min interval. Net cardiac cost (NCC) and relative cardiac cost (RCC) and limit for continuous work (LCW) were used as indicators of the cardiac strain. NCC was determined as the difference between resting heart rate (RHR) and WHR. RCC was obtained by expressing the heart rate at a given workload as the percentage of heart rate reserve (HRR) of a particular individual to depict the relative intensity of workload. It is calculated as: RCC = NCC / HRR * 100. [15],[16] Limit for continuous was obtained for individual worker by adding 30 beats with his resting heart rate. [17] For a more detailed insight into the workload, RCC was categorized into different class interval; 0-10, 11-20, 21-30, 31-40, and 41-50. The amount of time workers remained in these stress level was determined and expressed as percentage of the working period.

Recovery heart rate (RHR) was measured in a sitting posture. This was obtained by counting the pulse during the last 30 s of each minute in the first, second, and third minute of the recovery period, i.e. from 30 s to 1 min after work stops - recovery pulse 1 (P1 ), from 1½ to 2 min - recovery pulse 2 (P2 ) and again from 2½ to 3 min - recovery pulse 3 (P3 ). The PDI was calculated as the difference between third and first recovery pulse, i.e. P3 - P1. The following criteria were used for classification of the recovery pattern. [18]

  1. PDI ≤ - 10 beats per min and all RHRs below 90, then recovery is normal.
  2. PDI < - 10 beats per min and RP 3 > 90 beats/min, then it is considered as no recovery.


Each subject responded to a questionnaire regarding their annual, monthly and daily work engagement. On site observations were conducted for work study. This was done manually by a stop watch to record the duration of different tasks and rest pauses. No instruction was given to the workers to control their work method and work pace.

The following environmental variables were measured to assess heat stress prevailing in the work place.

Dry bulb temperature (T a)

Wet bulb temperature (T w)

Globe temperature (T g)

The dry and wet bulb temperatures were measured using an Assman Hygrometer. Globe temperature was measured using globe thermometer. Relative humidity (RH) was determined by the depression of wet bulb from a relative humidity table. All the environmental data were recorded at every hour in the work places throughout the shift in both the seasons.

Wet bulb globe temperature (WBGT) was estimated as the index of heat stress for the assessment of the thermal load prevailing in the work situation. This indoor application of this index was calculated according to the formula Yaglou and Minard [19] in the following manner:

WBGT = (0.7) T w + (0.3) T g

Students' paired t-test was used to compare seasonal (summer and winter) temperature readings and cardiac response between each group of workers. A comparison of cardiac response between groups was done by the unpaired t-test. A seasonal comparison of different variables of work load and physiological responses was done by the Wilcoxon signed rank paired comparison on 12 pairs of means for the younger group and 16 pairs for the older group of workers. Differences were considered statistically significant when P < 0.05.


  Results Top


The physical, physiological and professional characteristics of the subjects are summarized in [Table 2]. The height and weight of the workers are similar to the average population from eastern India.
Table 2: Physical, physiological and professional characteristics of confectionary workers (N=28)

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The seasonal variations of workers engagement and pattern of workload is summarized in [Table 3]. Working days per month was evaluated by the questionnaire study and the mean corresponds to the average value of 12 responses from the younger group and 16 responses from the older group. Other variables were obtained from on-site observation conducted for three workdays per worker.
Table 3: Characteristics of workload in confectionary work for young (YG) and older (OG) workers.

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Working days per month was higher for the older group in summer but similar in winter as compared to the younger group. Both the groups demonstrated a significant variation in different work periods in both seasons except total working hour and the period of rest pause, which were similar in both the groups during summer.

The productive period was higher and non-specific work periods were lower for the older group as compared to the younger counterpart in both seasons. Time spent by the older group in productive period varied between 83% and 85% of the total work shift. Rest periods were almost similar in summer for both groups. However, rest time was significantly more for the younger group in winter. Both the groups demonstrated a significant seasonal variation on these two variables.

Seasonal comparisons of cardiac strain indices are presented in [Table 4]. Descriptive statistics comprising mean and standard deviations are given from a total of 36 workers day observation for younger and 48 workers day observation for older groups.
Table 4: Comparison of cardiac strain indices during summer and winter for younger (YG) and older (OG) workers

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Mean WHRs were high in both seasons for both groups of workers. Irrespective of the groups, values of cardiac strain indices were significantly higher in summer. The PDI did not show any seasonal variation for the older group of workers.

Statistical analysis of the intergroup comparison revealed that except WHR, all cardiac strain indices were significantly higher for the older groups in winter. The RCC was the only parameter which was higher in the older group during summer.

Profile for RCC in confectionary work is presented in [Figure 1]. Profiles of both the groups were different in the two seasons. During summer, the RCC above 30 was recorded for 25% of the work shift in young workers and 47% of the work shift for older workers. In winter, the RCC was above 30 for 29% of work shift for the older group only.
Figure 1: Relative cardiac cost profiles of confectionary workers during the work shifts in summer and winter

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Young workers spent more than 50% of shift time at a RCC level of 21-30 during summer and 11-20 during winter. In contrast, for older workers, nearly 50% of work shift was spent at an RCC level of 31-40 in summer and 21-30 in winter.

Heat stress prevailing in the workplace is summarized in [Table 5]. Mean and standard deviations are calculated by clubbing the values obtained for both young (36) and older group (48) workers day. Seasonal comparisons were done by the paired t-test analysis between 12 pairs of summer and 16 pairs of winter means. This indicated that a hotter and humid thermal environment was prevailing in the workplace during summer. All the parameters measured showed a significant amount of difference in the seasonal comparison.
Table 5: Ambient temperature parameters in summer and winter

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The seasonal comparison of WBGT recorded during young and older worker workdays in two seasons is presented in [Figure 2]. The values significantly differ among the groups in summer (P < 0.05, unpaired t-test), but were almost similar during winter.
Figure 2: WBGT recorded in workplace during young and older group work days in two seasons

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  Discussion Top


The present study was exploratory in nature and was conducted in real work situation. This has permitted to obtain the integrated physiological reactions of the workers in response to different workplace stressors. The limiting factor for physical work seems to be the capacity of the cardiovascular system to meet the oxygen demands of muscles and thus heart rate is often used as an indicator of physical strain. Heart rate was chosen as the principal parameters because it provides an integrated response to energy requirement, thermal stress, and postural demand, [13],[18],[20] and also reflect the inter individual differences. [21],[22] These studies have also proved that the use of heart rate as a strain indicator is especially useful in workplace burdened with heat load. Heat stress increases heart rate because of increased cutaneous blood flow as a physiological mechanism for heat loss. The heat-induced heart increment above the work-specific heart rate reduced the reserve capacity of heart in proportion to the maximum attainable heart rate. This has oriented the choice of NCC and RCC as cardiac strain indices above the absolute heart rate to evaluate the cardiac strain of the workers in this study. The NCC being related to resting heart rate evaluates the work load strictly connected with the job, while the relative cardiac cost, which takes into consideration both the resting and maximum heart rate of the subjects, gives best expression of individual circulatory strain. [23],[24]

The heart rate reactions of the confectionary workers could also be compared with other organized and unorganized occupations in the Indian context. RCC for both groups of confectionary workers were comparable with women agriculture workers involved in reaping, binding, and threshing activities. [25] The values are also comparable with fishing [4] and die casting works. [9] However, RCC of both the groups were much lower than underground miners engaged in shoveling, carrying, and drilling task. [5],[6]

The physiological gradations of different activities have been proposed by researchers in the field of work physiology based on heart rate during work and recovery. Intensity of workload of the confectionary workers judged in accordance with the scales of heaviness based on WHR. [23] Based on this classification, the work load entailed in confectionary work could be classified as moderate in nature.

A WBGT of 27.5-28.5°C (81.5-83.3°F) has been recommended for "moderate" task with work periods ranging from 100% to 75% of total work shift for acclimatized worker. [10] In the present study, the subjects may be considered as acclimatized due to their full-time involvement in their job with a minimum work experience of 5 years. Moreover, all the subjects were regularly involved in their job for at least 2 weeks prior to the study. This had negated any possibility of short time acclimatization that might occur when away from heat for a short period and reduced heat tolerance. Therefore, taking into consideration the work-rest regimen of the workers throughout the shift, it appeared that the mean WBGT of 89.2°F during summer was above the recommended range and had imposed thermal load on them. However, the mean value of WBGT during winter for both groups was within the recommended range.

The present study design is based on seasonal comparisons. It intends to examine the combined effect of thermal and work stress on cardiac responses. It can be stated that the nature of workload in both seasons with subsequent variation in ambient temperature have influenced the magnitude of the physiological reactions for both groups in two seasons.

Studies have revealed a conspicuous variation in ambient thermal conditions in both the seasons in terms of WBGT. Some variations were also observed for differences in inter seasonal work periods. In summer, the total working and rest periods were similar for both the groups, with extended periods of productive periods for the older group. These variations in conjunction with increased heat load might have contributed to the higher level of cardiac strain for older subjects in summer. The no-recovery pulse patterns observed for both the young and older workers in summer reflected the combined effect of workload and thermal environment.

Although the heat stress level was within the acceptable range for both the groups in winter, the work periods were more for the older group as compared to younger counterparts. The increased amount of strain in older workers reflected in decelerated pulse recovery as compared to the normal recovery of the young workers could be attributed to the extra amount of work, thus reflecting cumulative fatigue and exhaustion in this season too as indicated in earlier studies. [18]

The magnitude of physiological strain for young workers in winter was within recommended range, the work periods are less as compared to summer. This finding may indicate that the winter values of cardiac strain of young workers might be representative of the baseline work-related hemodynamic efforts.

The present study work load was compared in terms of duration of different work periods. It would have been ideal if productivity could have been compared between summer and winter in order to quantify the difference in workload in both seasons. Unfortunately, due to the unwillingness of the owners of shops to reveal their actual productivity, the difference could not be empirically documented.

The work situation in the present study was not controlled; work was performed at a self-chosen pace. It is documented that in self-paced work, workers adopted themselves to work so as to regulate the strain on their cardiovascular system. [22] In the present study, although evidence of cumulative fatigue was obvious from delayed recovery particularly in summer, RCC of the workers were within recommended limit which indicated a similar type of adaptation to work. Moreover, the entire days work comprised of different task, which vary in their intensity level. These tasks were conducted both in summer and winter. A combination of these works throughout the work shift interspersed with periods of rest pauses might have prevented the worker from experiencing an extreme level of cardiac strain.

The work exposure time of the confectionary workers appeared to be much higher than the industrial situation with work spanning for eight hours per day. The present study has reported the work stress related to the day time work. Emphasis should be given to the point that in this unorganized sector, the work is resumed during evening, when the workers were re-exposed to heat of the cooking ovens. The heat exposure limits suggested for industrial situation therefore should be reduced to a lower level for this group. It has been suggested to reduce the permissible exposure time for subjects from industrially developing countries. [26] It can be well apprehended that extensive working hours in confectionary work in conjunction with increased heat load particularly in summer season, had imposed a considerable amount of physiological strain particularly on the older workers. The majority of the workers in the unorganized sector are from the indigent part of society and a lack of awareness on health and safety issues is very common among these groups. This in turn has made them very much unaware about the balance between their work ability and job demand as had shown earlier. It was also pointed that they are more likely to be affected by diseases prevailing in the community [26] and thus considered less healthy.

A cursory examination of work place also revealed poor housekeeping, illumination, and ventilation of the different workplaces studied which have also contributed in increasing the work stress.

The present study can be extended to evaluate the work load entailed in a whole work day, along with specific physiological stress connected with an individual task. By cursory examination, ergonomic stressors were identified in workplace as well as in connection with individual tasks. These identifications necessitate an ergonomic intervention which indicates further scope of the study. The authors strongly felt that an occupational health and safety awareness program is urgently required for an unorganized group of workers in the context of developing country.


  Acknowledgement Top


The authors wish to express their appreciation to all the shop owners for their sincere cooperation. The authors are also duty-bound to express their gratitude to all the confectionery workers who volunteered in the study.

 
  References Top

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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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