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Glob Health Action. 2010; 3: 10.3402/gha.v3i0.5635.
Published online 2010 November 29. doi:  10.3402/gha.v3i0.5635
PMCID: PMC2997729

Case studies on heat stress related perceptions in different industrial sectors in southern India


Linkages between thermal loads and its physiological consequences have been widely studied in non-tropical developed country settings. In many developing countries like India, despite the widespread recognition of the problem, limited attempts have been made to estimate health impacts related to occupational heat stress and fewer yet to link heat stress with potential productivity losses. This is reflected in the ubiquity of workplaces with limited or no controls to reduce exposures. As a prelude to understanding the feasibility of alternative interventions in different industrial sectors, we present case studies from 10 different industrial units in Tamil Nadu, Chennai, which describe perceptions of occupational heat stress among the workers and supervisors/management.

Units were selected from among those who had previously requested an assessment of workplace heat stress exposure at select locations as part of routine industrial hygiene services provided by the investigators. Since the earlier measurements were performed in response to a management request, all units were revisited to generate a simple job and process profile using checklists in order to understand the overall heat exposure situation in the concerned unit. This was followed by a simple questionnaire administration to a small subsample of employees to evaluate the perceptions of workers and supervisors/management. Finally, we retrieved available quantitative data from previous measurements of heat stress at these units to correlate prevalence of exposures with respective perceptions.

Results indicate that the existing level of controls may not be sufficient for managing work-related heat stress in any of the sectors studied, with wide variations in perceived risks. There was a noticeable disconnect between worker's perceptions and their ability to secure workplace improvements related to heat stress from the management. Wider availability of engineering and administrative controls in the industries may be facilitated by monitoring worker discomfort, disability, and performance in more intensive ways so that the top management is able to justify the associated cost benefits.

Given the potential implications of future climate change related increases in ambient heat stress that are likely to translate into workplace exposures in developing country settings, concerted efforts are needed to integrate exposure assessments with assessments of productivity as well as health impacts. This will likely build the momentum for much needed interventions for large worker populations in the developing world.

Keywords: heat stress, perceptions on heat stress, productivity loss, health effects of heat stress

Heat stress has been identified as a widely prevalent health risk in many industrial sectors in India (16). Combined effects due to excessive heat stress and ergonomic hazards (like heavy lifting, physical exertion, and others) pose great challenges for workers in being able to optimize their productivity, with the potential risk of ensuing heat-related disorders like heat stroke, heat exhaustion, heat cramps, and heat syncope. However, limited attempts have been made to create detailed job exposure profiles for various sectors that may facilitate such hazard recognition. With most workplace settings in developing countries being heavily influenced by outdoor temperatures (in the absence of mechanical cooling), it can be expected that both indoor and outdoor work may contribute to greater than recommended levels of heat exposure. Inadequate recognition of this hazard potential has hampered efforts to assess health impacts related to heat stress and/or implement controls to reduce exposures.

Building on earlier efforts in single industrial units to control heat stress exposures (7), an assessment of risk perceptions among workers and management across different sectors was conceptualized to provide a deeper understanding of factors that influence the investment in heat stress reduction strategies in individual companies. Such an exercise would also provide insights into how health risks and/or productivity losses in relation to heat stress may be assessed on a routine basis to facilitate risk communication and subsequent management. Finally, heat stress associated with climate change has been most often examined in relation to heat wave effects on the general population and have overlooked working populations. Recognition that climate change may precipitate occupational heat-related health risks with related impacts on productivity especially in developing countries is yet to develop. The need for the design of effective intervention strategies thus becomes even more important in the face of current and future climate change.

With a view to capturing perceptions that may play an important role in determining the availability/accessibility of control (preventive) measures for management of occupational heat stress, we present case studies from 10 different industrial sectors in Tamil Nadu in India that describe a range of perceptions on occupational heat stress. These case studies describe the nature of the job processes, available exposure information, an overview of the available control measures, and perceptions of workers and supervisors/management on heat stress in these sectors.

Materials and methods

Perceptions were assessed among workers, managers, and other health and safety professionals in area industries where heat stress measurements had been previously made as part of routine industrial hygiene monitoring by the same investigators. Ten such companies that were involved in automobile assembly, automobile parts manufacturing, heavy truck manufacturing, heavy vehicle (lorry) manufacturing, automobile parts (wheel) manufacturing, leather manufacturing, glass manufacturing, textiles, fertilizer, and electricity (power) generation were selected for the present assessment.

A simple job and process profile was first generated for all facilities to allow an overall understanding of the prevalence of heat exposure situations in companies. A small subsample of workers (~1–5% of the total worker strength) from select work locations where heat stress monitoring had been performed were first selected for administration of a questionnaire to assess perceptions (some of the units assessed have had a long history of routine heat stress monitoring while others have been assessed only on a single time basis). In addition, select workers from other locations, the safety and/or medical officer (if available), and work supervisors/senior management were included for the assessment. The selection of the participants from other categories was based on the premise that they would be able to respond to management relevant questions and would be aware of company policy on the issue. The response rate ranged from 60% among workers to 95% among other categories. The questionnaire elicited responses pertaining to how workers perceived the heat stress problem in terms of symptoms experienced, productivity/performance changes, the availability of controls, their awareness on heat stress management, and the availability of specific company policies for management of heat stress.

Heat stress exposure was assessed (during previous visits to the same companies) through measurements of the Wet Bulb Globe Temperature (WBGT) index. The WBGT index primarily estimates the environmental contribution to heat stress and is influenced by air temperature, radiant heat, air movement, and humidity. Since the WBGT index primarily reflects environmental contributions, recommended exposure criteria are adjusted for the contributions of work demands and clothing.

Measurements for WBGT were carried out using an area heat stress monitor (Model QuesTemp°34, manufactured by Quest Technologies, USA). The instruments used for the measurements comply with the standards set out by the American Conference of Governmental Industrial Hygienists (ACGIH). Additional information on workload, clothing worn, worker's time-activity pattern, and acclimatization were collected on-site by the trained industrial hygienists and occupational health specialists to make appropriate adjustments to the measured WBGT value.

A total of 242 questionnaires were administered and heat stress measurement data on nearly 80 work locations were retrieved to assess perceptions in relation to prevalent exposure situations and generate initial recommendations for next steps. All questionnaires were administered by research assistants with experience/special training on occupational hazard recognition and control.


Results of quantitative and qualitative assessments conducted at the 10 facilities are furnished in Table 1.

Table 1
Results on worker's and management's perceptions


The results described in the previous section clearly convey the wide variation in the nature of perception prevalent among workers and management across multiple industrial sectors. Despite the range of differences, listed below are some summary observations that convey the overall results of the assessment.

All companies (with the exception of one) assessed were in possession of some form of environmental or occupational health certification indicating a general awareness among local companies for occupational safety issues (especially since such certifications are not required for local legal compliance). However, the importance accorded for heat stress as an occupational health issue was rather low. Although in many cases measurements were requested to satisfy certification requirements, there was little correlation between the prevalence of the problem and the level of follow-up of recommendations for implementation of appropriate exposure mitigation strategies.

The levels wherever and whenever measured usually exceeded recommended exposure levels, but there was little or no integration with either control or health surveillance efforts. This was despite the availability of a well-equipped health center being available at many facilities.

Most locations where heat stress was measured were indoors with no process generated heat components indicating that heat stress exposure may be a facility wide problem and not limited to the locations monitored (as a result of primary contributions from high ambient temperatures). This has important implications for the scale of expected exposures and related impacts that could be grossly underestimated by including only industrial processes with process generated heat as sources of occupational heat stress. There were also a few cases of personal protective equipments (PPEs) not being used to avoid excess heat indicating potential for risks from heat stress spilling over to additional risks from chemical exposures.

Most workers recognized the problem and wanted some improvements but had limited abilities to influence their management. Some workers in fact felt this would allow them to maintain/enhance their productivity. Management often felt that the levels of controls in place were adequate and that in the absence of extreme health events (such as heat stroke or exhaustion) there was little need for additional measures to reduce exposures. There were few facilities that despite several heat stress related incidents did not engage in additional exposure controls but instead were satisfied with their health center being able to manage the episodes. Possible links to productivity losses were not recognized until prompted. While many workers felt they were not able to slow down, management was either unaware or surprised at the possibilities of such impacts on productivity as opposed to health.

Finally, heat was perceived to a ‘common’ and a ‘general’ problem, an issue of special concern for risk management in tropical settings. High levels of ambient heat are encountered in occupational and non-occupational settings. Since in many work locations this heat is not process generated, management does not feel obligated to control an exposure that the workplace did not generate. The linkages to health and welfare remain distal and it seems to be expected that workers would need to bear the heat and maintain productivity.

A summary that consolidates the main results and the ensuing discussion are provided in Table 2.

Table 2
Results on the status of heat stress exposure in different industrial sectors


While many previous studies (17) have reported prevailing heat exposure levels in India, to our knowledge a perception survey has not been carried out thus far. The preceding discussion emphasizes the fact that the existing levels of exposure mitigation do not appear to be sufficient for managing work-related heat stress in any of the sectors studied. Limited awareness on the need for preventive measures for heat stress seemed to be prevalent among management despite widespread reported discomfort by workers. There was a noticeable disconnect between worker's perceptions and their ability to secure workplace improvements related to heat stress from the management. Wider availability of engineering and administrative controls in the industries may be facilitated by monitoring worker discomfort, disability, and performance in more intensive ways so that the top management is able to justify the associated cost benefits. In some sectors, management did express interest in collecting data relevant to absenteeism and examining its relationship with heat stress especially during peak summer and this may afford an important opportunity to establish linkages to productivity. Linkages to productivity have been recently demonstrated in other countries (810). Similar quantification of such productivity losses may allow leveraging of worker interests with that of the management in feasible ways.

It needs to be emphasized that this assessment was carried out in large organized manufacturing units, a work environment setting that eludes millions of workers who are largely employed in the unorganized or small and medium enterprise (SME) units within industrial and non-industrial sectors. The magnitude of the problem as presented here may thus just represent the tip of the iceberg for a much larger and deeper impact. It is in this context that examination of this issue from a climate change point of view becomes important. Even relatively modest increases in ambient temperatures (such as the current lower end projections of 2–3°C) could be expected to tip large worker populations exposed to ‘near limit values’ of heat stress over the threshold into the realm of experiencing heat stress related health risks. The reduction of physical ‘work ability’ due to increasing heat exposure has been well documented in international guidelines such as ISO, 1989. Pilot studies have shown that there is not much work ability left between the hours of 10:00 and 17:00 during typical May days for construction workers in New Delhi, who often have to take 5 h rest breaks to cope with the heat (8). It could be easily expected that many workers are already losing substantial hours to reduced or no productivity and this would only worsen if ambient temperatures were to rise.

The National Institute of Occupational Health in India has undertaken extensive research on the physiology of heat exposure and preventive approaches of relevance for Indian work settings. Using experimental exposure chambers, their studies quantify the ‘tolerance time’ of work at different intensities until core body temperature reaches 39°C. At a WBGT of 34°C, the tolerance time for heavy work goes below 1 h and it reduces by 4–5 min per 1°C increase of WBGT (2). Given the propensity of workplaces at this or in excess of this threshold of exposures, any increases that climate change may precipitate could be expected to have serious impacts on workers health and productivity.

Concerted efforts would thus be needed to profile exposures in multiple work settings and link it with potential impacts on productivity and health. It is hoped that the results of this exercise serves as a pilot to scope larger efforts that can build the momentum for much needed interventions for large worker populations in the developing world.


We thank Professor Tord Kjellstrom for his technical guidance in presenting the case studies in the form of this manuscript. His insights in interpreting the results in the context of implications for efforts to control this pervasive and yet largely unrecognized occupational health hazard as well as potential linkages to future climate change mediated impacts on worker productivity were immensely useful. The authors are grateful for his patient involvement. Source(s) of support: Sri Ramachandra University, Chennai.

Conflict of interest and funding

The authors have not received any funding or benefits from industry or elsewhere to conduct this study.


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