Indoor Workforce at Workplace
Indoor workplace could be doing more harm than good in your company output. With predicted increasing frequency and intensity of extremely hot weather due to changing climate, indoor workplace heat exposure is presenting an increasing challenge to occupational health and safety.
For example, how much time do we spend indoors every day? 10 hours? 15? Try more than 21 for the average working Kenyan. That’s about 90 percent of the day. Whether we’re at home resting or working; visiting others; at the office, at the workplace; in cars, buses or trains; at school; in stores, fitness centers, churches, health care facilities and more; all indoors. And most people don’t realize how buildings and what’s in them affect our health and well–being.
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Predictions to Poor Indoor Workforce
All published epidemiological studies in the field of health impacts of indoor workplace heat exposure for the period from January 1997 to April 2012 were reviewed. Finally, 55 original articles were identified. Manual workers who are exposed to extreme heat or work in hot environments may be at risk of heat stress, especially those in low-middle income countries in tropical regions.
At risk, workers include farmers, construction workers, fire-fighters, miners, soldiers, and manufacturing workers working around process-generated heat. The potential impacts of workplace heat exposure are to some extent underestimated due to the underreporting of heat illnesses. More studies are needed to quantify the extent to which high-risk manual workers are physiologically and psychologically affected by or behaviourally adapt to the indoor workplace heat exposure exacerbated by climate change.
How the Indoor Workplace is Affected
Many ecological studies have revealed that extremely hot weather contributes to excess morbidity and mortality in the community. Most of the extreme heat-related research has traditionally focused on vulnerable populations including the elderly, children and patients with chronic diseases and those on certain medications.
Extremely hot weather also places many types of indoor and outdoor manual workers at increased risk of heat-related illnesses and injuries. Increased concerns about the environmental heat-related impacts of climate change on population health have been raised since the late 1990s.
The Indoor Workforce internal Aspects
Heat gain can be a combination of external heat from the environment and internal body heat generated from metabolic processes. There are two types of external heat exposure sources in the workplace: weather-related and man-made heat exposure. With predicted increasing frequency and intensity of heatwaves, weather-related heat exposure is presenting a growing challenge to occupational health and safety.
Research Sources on Indoor Workplace
All published epidemiological studies in the field of health impacts of workplace heat exposure for the period of January 1997 to April 2012 were reviewed, utilizing the searching strategy of a random combination of the first keywords [tiab] and the second keywords [tiab]. The field code ‘tiab’ is the abbreviation of ‘title or abstract’. All academic articles containing search keywords in the title or abstract were retrieved. In our case, the search topics were (Indoor Workplace).
The first keywords included climate change, heat stress, heatwave, heat exposure, extreme heat. The second keywords included workplace, workers and occupational health and safety. Literature databases used for this review ranged from PubMed (biomedical sciences), Scopus, ScienceDirect, and Google Scholar. Only original research articles published in English in peer-reviewed journals were included, whereas review articles, editorials, letters, conference abstracts, and government reports were excluded.
Impacts of Indoor Workplace to susceptible occupants
Without adequate heat dissipation, short-term acute extreme heat exposure can cause a rise in core body temperature and may result in direct heat illnesses. Adverse long-term health effects of chronic workplace heat exposure have also been reported such as cardiovascular diseases, mental health problems, and chronic kidney diseases.
In addition to work-related illnesses, indoor workplace heat exposure can also increase the risk of occupational injuries and accidents. Core temperature elevation and dehydration have had negative behavioral effects such as physical fatigue, irritability, lethargy, impaired judgment, vigilance decrement, loss of dexterity, coordination, and concentration, potentially leading to a compromise of occupational safety.
The characteristics of workplace heat exposure may vary in different occupations. For large-scale workforce in workplaces, we have provided you with a summarized version as below. The impacts of heat exposure can be particularly harsh on outdoor workers such as those in agriculture, construction, mining, and manufacturing industries. As well as the armed forces personnel and fire-fighters as discussed below.
Agriculture is one of the industries at the highest risk of heat-related illness and injury. Farmers are often exposed to outdoor heat extremes for long periods of time, and often there is a lack of occupational health and safety programs. In Kenya, agricultural industries have the third highest rate of heat-related deaths among all industries, with a mortality rate of approximately 20 times greater than for all civilian workers.
Workplace heat exposure
In terms of heat-related morbidity, farm workers have been shown to be four times more likely than non-agricultural workers to suffer from heat-related illnesses in Kenya. Currently, published literature assessing farmers’ heat stress status is limited. Mirabelli 61)identified that 161 heat-related fatalities occurred from 1977 to 2001 in North Carolina US by reviewing medical records, and found that 45% occurred among farmers.
In another study by the same author, it was found that approximately 94% of farmers reported working in extreme heat, among which 40% experienced heat stress-related symptoms. At the time no regulations and prevention measures were available for preventing heat exposure. A study of 124 Japanese forestry workers showed that 32.3% had reported symptoms of heat illness37). With low levels of mechanized farming and motivation by payment based on work output, agricultural workers in low-middle income countries may be at relatively higher risk of heat exposure31, 52).
In the building industry, several contributing factors increase the risk of heat-related illness and injury. These include the constant use of machinery and powered tools, working on elevated surfaces, heavy workload, simple accommodation conditions near work sites, being temporarily employed by a sub-contractor on a daily payment basis, and constant and direct exposure to sunlight.
From 2003 to 2008, the US Census of Fatal Occupational Injuries recorded 196 heat-related mortalities, and construction workers occupied the greatest proportion (36%)12). A self-administered questionnaire among 115 Japanese male construction workers in summer demonstrated that in terms of heat-related subjective symptoms, up to 63.7% of workers reported ‘feeling thirst’ at work, followed by 42.2% reporting it was ‘easy to get fatigued’, 41.2% reported ‘waking up early due to hot conditions’, 31.9% reported ‘impatience’, 13.2% ‘a headache’, and 11.8% ‘dizziness’20).
Those symptoms are consistent with the hypothesis that heat exposure may increase the risk of occupational accidents and injuries. In Taiwan62) and Thailand23), temporarily self-employed construction workers reported suffering from severe heat strain because of physically demanding work and hot accommodation conditions in dormitories near construction sites. However, if preventive measures are sufficient in building sites, workers could avoid heat-related symptoms.
Extreme heat exposure
A cross-sectional study has been conducted among 12 male workers in a Japanese hydroelectric power plant building site with WBGT often exceeding the recommended exposure limit values most of the time on a typical hot day in summer25). However, there was no significant change in subjective symptoms, serum electrolytes, blood pressures and heart rates before and after work, because preventive measures had been taken. These included temporary tents for rest, electric fans for ventilation, and automatic machines for cool drinks.
There should be caution in the interpretation of the results because of the small sample size and the fine weather conditions during the two days investigation period. Apart from common preventive measures, self-pacing can also be an effective way of reducing the risk of heat-related illness and injury as reported in a study of construction workers in the United Arab Emirates24).
Hot working conditions in mines are very common and vary according to the type of mining. For opencut mines, heat exposure is similar to other outdoor workplaces. However, by far most problems of heat stress have been reported from underground mines as additional heat from virgin rock and mines increase with depth. Furthermore, air auto-compression for ventilation adds about 6°C dry bulb temperature per 1,000 m of vertical depth49).
Long hours underground
High humidity from water required for dust control also contributes markedly to the thermal load. The incidence of heat illness in underground mines has been reported to be higher for metal mining than for coal mining as underground metal mines are usually much deeper than coal mines in the US14). The incidence rate ratio of heat exhaustion for deep mines below 1,200 m compared with above 1,200 m was 3.17 in Australia7).
According to the 1983–2001 data from the US National Institute for Occupational Safety and Health, most heat illness cases in mines occurred during dayshift hours rather than night shift hours14). This is to be expected for surface mining given the higher air temperatures during the day. But for underground mining, there is lack of convincing reasons for more heat illnesses during dayshift hours even after considering the greater proportion of dayshift workers than nightshift workers, because there is no significant change in temperatures in underground mines between day and night due to thermal damping effects.
Illness through extreme heat
Brake and Bates50) suggested that the normal diurnal variation of body internal temperature, which is relatively lower at night, may contribute to the lower risk of heat illness on a night shift. The effects of seasonal change on underground temperatures decrease with the increase of mining depth. Hence, heat illnesses may occur throughout the year and with less incidence rate in non-warm seasons. Even so, most heat illnesses have been reported in summer seasons7, 14). Therefore, surface temperature forecasts can also be useful for warning miners and management about the risk of heat illnesses.
In some low-middle income countries, miners with heat illness symptoms may still keep working in extremely hot environments due to relatively low perceptions of prevention strategies, lack of protective measures, and income incentives, which may result in the occurrence of life-threatening heat strokes. In South African deep underground gold mines, heat stroke has been an endemic hazard since before the 1970s. In recent years due to acclimatization and prevention measures, the incidence rate of heat stroke has been declining significantly63). The occurrence of heat stroke is reportedly relatively rare currently but still remains unresolved.
Stroke from thermal effects
In high-income countries, heat stroke cases are seldom reported in mining industries. In an Australian deep underground mine with about 2,000 miners, no heat stroke cases had been reported to the 24-h on-site medical clinic during over 10 million work shifts in the period 1966–199750). Similarly, there were no cases of heat strokes reported in 1983–2001 in the US mining industry14). Several reasons may contribute to the few occurrences of heat stroke cases in high-income countries.
Firstly, this may be attributed to a flexible management approach and the resistance of miners to continue strenuous labor in severe thermal conditions. Secondly, most miners are assumably well-trained about the effects of working in the heat. Thirdly, in high-income countries miners suffering heat-related illnesses generally report their conditions actively and cease mining7). Finally, it may result from self-pacing47).
Miller et al. even suggest that self-pacing should be encouraged as a protective behavior without productivity compromise in the mining industry21), as nowadays many tasks in mining are highly mechanized and a reduction of workload may not necessarily result in productivity loss.
Armed Forces Personnel
Most epidemiological studies on military populations have focused on specific military bases for relatively short periods and with relatively small populations16). At present, heat-related morbidity and mortality analyses of military personnel data are based on consulting military hospital records15, 64, 65). Over time there has been a downward trend of heat illness hospitalization rates due to preventive measures in the US Army15).
The total number of hospitalizations for heat illness reduced by 60% in the 22 yr period of 1980–200215). However, heat stroke rates have markedly increased eightfold15). The possibility is that preventive measures might allow compromised soldiers to avoid minor heat illnesses and continue to exercise until more severe heat stroke occurs. Regarding the proportion of heat illness spectrums, almost 60–70% of heat illness cases were due to heat exhaustion and 13–18% for heat stroke15, 66).
The percentage of mild heat illnesses is small as individuals may recover rapidly in the field without being hospitalized. Infantry soldiers had the greatest risk of heat illness in the US in the period 1980–200215), whereas soldiers in administrative and support jobs had the lowest risk. In addition, ethnicity, gender, fitness level, and geographical origin are related to heat illness occurrence in military populations.
Caucasians are more vulnerable to heat illness than African Americans and Hispanic Americans15). Soldiers from the northern US are more susceptible to heat illness than those from the southern US, and female soldiers are at greater risk of heat illness than male soldiers15).
Fire-fighters are required to wear fire-fighting protective clothing and self-contained breathing apparatus regardless of environmental temperatures. This personal protective equipment can reduce the effect of heat dissipation and increase the risk of heat stress.
Recently, based on simulated trials among 70 volunteers recruited from the Toronto Fire Service, the replacement of the duty uniform long pants and shirt with shorts and T-shirt has been recommended by McLellan and Selkirk34, 35), as it could significantly reduce heat strain and extend at least 10–15% heat exposure time. But it raises concerns about whether the replacement of long pants with shorts may put fire-fighters at greater risk of injury.
Evidence from the New York City Fire Department proved that not only were the burn incidence and severity not affected, but also the days lost due to heat illnesses were significantly reduced67). In a simulated fire-fighting drill among 16 male fire-fighters from a Fire Service Institute in the US, higher blood lactate levels, longer recovery time, and significantly increased heart rate and core temperature were observed after performing tasks in a live fire environment than after performing the same tasks in a non-fire environment36).
In the same study, it was shown that the psychological impacts of emergency conditions are also a problem for firefighters. A dramatic increase in anxiety level immediately following firefighting activities was found36). Elevated anxiety status may impact on cognitive performance, resulting in inappropriate decisions that might increase of risk of injury. Interestingly, the relationship between perceptions of heat illness and heat strain varies by thermal conditions.
In non-hot conditions, the correlation coefficient was moderately positive (r=0.57–0.48), however, there was a little relationship (r=0.01–0.18) in hot conditions. If perceived risk of heat illness is underestimated, fire-fighters may put themselves at greater risk. But there is a probability that it may result from information bias that participants were unwilling to report their real feelings because of peer pressure36).
Manufacturing workers in non-air conditioned indoor workplaces are also at risk of heat-related illness despite little or no direct sunlight radiation. The levels of heat stress can be very high in workplaces surrounding hot machines, furnaces, ovens, and molten metal. Even in winter, the temperatures near furnaces in a steel plant have ranged from 35.5 to 46.5°C when the outdoor temperature was only 14–18°C58).
Climate change strenuous environments
Increased hot days due to climate change may worsen the extent of heat stress for individuals working around the heat generating sources. Hence, many epidemiological studies have focused on the impacts of workplace-generated heat on factory workers in steel plants13, 59), foundries42), automobile industries43,44), and glass manufacturing units41).
Excessive industrial heat exposure is associated with dyslipidemia42), cardiovascular and digestive diseases68). However, a cohort study in a French stainless steel producing plant showed that cardiovascular disease mortality was 10% lower for the workers exposed to heat than for a control group that was not exposed69). The negative relationship between heat exposure and mortality may result from the ‘healthy worker effect’ due to the stringent selection criteria when recruiting workers.
Indoor Workplace Precautions and Measures
If the predictions about likely future temperature increases prove reliable, weather-related extreme heat exposure is placing many types of indoor and outdoor workers at increasing high risk of heat-related illnesses and injuries. For acclimatized manual workers, a few degrees of climate change can make dangerous days increase to 15–26 d per year in 2070 compared to 1 day per year at present in Australia70).
Outdoor workers, in particular, those undertaking highly intensive and physical activity under the sun are susceptible to heat stress during heatwaves when preventive measures are not adequately adopted20, 22, 25,26, 30,31,32,33, 37). Physical and strenuous activity generating internal body heat load with increasing metabolic rate, together with significant radiant heat load from direct sunlight may further worsen heat stress.
Indoor workers, especially those working around furnaces, ovens, smelters, and boilers, are at a higher heat stress risk on hot days34,35,36, 57, 58). Despite indoor workers not being exposed to direct solar radiation, they can be exposed to heat and humidity generated from work processes or equipment. Their working environment can also become very hot when a cooling system is not available or ventilation is insufficient during hot days58).
- Workplace Safety Check
This review of the health impacts of workplace heat exposure has examined 55 epidemiological studies published between January 1997 and April 2012. Due to the availability of occupational health and safety data, all surveillance data based articles have been from high-income countries. Although the underreporting of work-related injuries may challenge the data quality and affect the reliability of results, it still provides a good overview of the characteristics of occupational health and safety in the workplace.
- Workplace Timings
About three-quarters of the articles simply described the distribution of heat-related illness or injuries by industrial sectors, occupations, seasons, and months, etc. Undoubtedly, most of heat-related illnesses and injuries occurred in summer months and hottest parts of a day according to previous findings10). There is a lack of further data analyses exploring the association between temperatures and heat/work-related injuries.
- Workforce Curvings
Theoretically, the number of work-related injuries is positively related to the increase in temperature. It has been characterized as U, V, and J-shaped curve relationship. Practically, however, preventive measures may be adopted in the workplace or workers may stop work or self-pace if the workplace temperature is extremely high. It can result in the unexpected decline in the number of work-related injuries, which is described as reversed U-shaped curve9). But if denominator information is available for calculating work-related injury rates, the relationship still appears to be U-shaped curve47).
The relationship patterns between temperatures and work-related injuries may vary by industries, gender, and age group. For example, young workers aged less than 30-yr-old showed consistently higher injury rates than other age groups in all thermal categories47), which may be related to the practice of assigning young workers with more physically demanding work.
- Wellness Survey
More epidemiological analyses based on occupational injury surveillance data are needed to quantify the extent to which high-risk manual workers are affected by workplace heat exposure, and to identify risk factors for workplace heat prevention and adaptation, especially for low-middle income countries in tropical regions3). This is achievable if there is a routine occupational injury surveillance system and it may also provide epidemiology-based evidence for the decision of heat alert temperatures in the workplace.
There are several points worth noting when analyzing the temperature-occupational injury relationship, including the selection of appropriate regression models, the adjustment of confounding factors, and the handling of a non-linear relationship. Among these reviewed articles, only three papers used Poisson regression suitable for count data9, 13, 15). However, none reported checking whether the distribution of work-related injuries was over-dispersed or not, in which case negative binomial regression is more appropriate.
- Work Leave & Off Duty
It also applies for the selection of family functions when using GEE (generalized estimating equation model). In terms of confounding factors, amongst the reviewed articles only Morabito9) took a public holiday, weekend, and time-lag effects into account, whereas the long-term variation trend and day of the week were not adjusted. As to the problem of non-linearity, piecewise linear regression or linear spline function has been adopted by dividing temperature ranges into several pieces9, 13).
Usually, the number of reported heat illness is very small. In Australia, statistics show there were 485 compensation claims due to exposure to environmental heat in the 11 yr period of 1997–200771). Similarly, 480 heat-related compensation claims were identified during the 11 year period of 1995–2005 in Washington State, US10). If just based on the reported statistical figures, it is not surprising that heat stress is not listed as an occupational health priority. But it should be noted that heat-related illnesses may be underreported largely due to following reasons.
Firstly, many high-income countries utilize workers’ compensation claims to measure occupational health and safety performance. However, the compensation based data does not provide any information for groups not covered by workers’ compensation schemes, such as some self-employed workers. Secondly, some workers with minor injuries may not apply for compensation claims. Most heat illnesses are mild and individuals recover rapidly through simple treatment or rest on site without hospitalization.
Thirdly, because heat exposure can exacerbate existing medical conditions, illness or death due to heat exposure may be preceded by other diseases and reported as other diseases other than heat illness. Additionally, the criteria used to determine heat illness and death vary largely, resulting in misclassification. Overall, it should be realized that the huge potential risk of heat-related injury and accident may be disguised by the underestimated number of heat-related illness and death.
In contrast to surveillance data analyses, most cross-sectional field surveys aiming to investigate heat stress status and workers’ physiological responses to heat are from low-middle income countries in tropical regions22, 31, 33, 41, 43, 44, 52, 53). It is consistent with the regional maps proposed by Hyatt72), predicting regions at high risk of occupational heat exposure.
- Indoor Workplace Psychology Evaluation
With global climate change trends, extreme workplace heat exposure situations may extend to large areas of the world apart from Australia, South Asia, Southern Africa, Central America, and the southern US. A majority of the studies show that workplace heat stress exceeds the heat stress criteria of the American Conference of Governmental Industrial Hygienists and is presenting a threat to manual workers’ health and safety.
Usually, physiological responses and subjective symptoms of industrial workers exposed to heat include elevated blood pressure and urine gravity, increased recovery heart rates and body temperature, and increased fatigue symptoms25, 34, 36, 47, 48, 51, 54,58). However, if effective prevention measures are taken in the workplace, the risk of heat-related illness and injury can be significantly reduced20, 24, 57, 59).
Workers’ self-pacing has been found to reduce heat strain in construction and mining industries in Australia50, 51), Germany47), and the United Arab Emirates21). Currently, there is no consensus about whether self-pacing should be encouraged in the indoor workplace. Positive self-adjustment of work pace to a safe level could be considered as a flexible management approach to maintain productivity without compromising workers’ safety in hot environments21). This can be subject to the conditions that the task has no urgent character and does not involve work output based payment incentives, that workers should be well trained in their job, and that self-pacing may be associated with close supervisory surveillance73).
On the contrary, if self-pacing is workers’ passive physiological or/and psychological reactions to thermally stressful conditions by slowing work pace, it may be inefficient either in terms of productivity or in terms of heat strain reduction. Evidence from field studies in Australia has suggested that few workers will voluntarily work at a pace that requires an average heart rate over 110 bpm for any length of time50), a level consistent with WHO recommendation74).
- Regulations and Resultant Measures
Therefore, working in a hot environment is not only a matter of occupational health and safety, but also an area involving all levels of society economically: individual, family, community, regional, and national levels75). In addition, there are few studies to investigate how decision makers, hygienists, employers, supervisors, workers, and relevant stakeholders perceive the role of self-pacing for reducing the risk of heat-related illnesses and injuries in the workplace. This can be important for the formulation of self-pacing related guidelines and regulations and more studies in this area should be encouraged.
Regarding gender differences in workplace extreme heat exposure, more evidence is required. Women have a lower sweat rate than men, which is disadvantageous in hot-dry environments, but advantageous in hot-wet environments76). It was reported that there was a higher risk of heat-related injury occurred in women performing National Guard duties during a Midwest flood rescue operation in the US in 199377).
One qualitative study from South Africa showed that women felt they could not cope with hot weather as well as men did, especially when they had to undertake labor-intensive work52). However, if cardiovascular fitness level, aerobic capacity, surface area-to-mass ratio, and the extent of acclimation are standardized, the distinctions tend to disappear78).
With predicted increasing frequency and intensity of extremely hot weather due to climate change, indoor workplace heat exposure is presenting an increasing challenge to workers injuries and heat-related illnesses. Manual workers who are exposed to extreme heat or work in hot environments may be at risk of heat stress, especially for workers in low-middle income countries in tropical regions.
Those workers include farmers, construction workers, fire-fighters, miners, soldiers, and manufacturing workers working around process-generated heat. If effective prevention measures are taken in the workplace, workers may not be physically challenged by heat stress. The potential impacts of workplace heat exposure are to some extent underestimated due to the underreporting of heat illnesses and the lack of awareness that heat exposure can increase the risk of work-related injuries.
Whether you consider your workplace safe or not, it is important to look into even finer details in regards to your general health. The research is not only motivated by the higher risk workforce but even those considering themselves safe. There are various conditions or workplace environments that may have a huge impact on our wellness if not well addressed. If you were pleased by this research article, please don’t forget to share with a friend.
Context and Research Material References.
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