Heat Stress Of Workers Research Articles

Evaluation of heat stress of workers using wearable biosensors in protected horticulture

Evaluation of heat stress of workers using wearable biosensors in protected horticulture

The influence of occupational heat stress on serum inflammatory cytokines among traditional bakery workers in Iran.

Heat exposure exceeding the ISO7243:1989 standard limit can contribute to health problems among employees in a variety of workplaces. Ignoring heat standard requirements in hot working conditions such as bakeries results in physiologic and health problems, as well as an elevated risk of later illnesses. In this analytical case-control study, the serum levels of four inflammatory factors (interleukin-1 beta, interleukin-6, tumor necrosis factor-α, and C-reactive protein) were assessed using an enzyme-linked immunosorbent assay. 105 male artisan bakers (in four job classifications in bakeries and staff) were compared based on demographic characteristics and inflammatory factors. The findings of the study showed correlations between serum interleukin-1β, interleukin-6, and C-reactive protein levels and thermal exposure in the occupational environment and employment type. Moreover, some differences in serum level of interleukin-1β and job type were observed. Heat overexposure affected the increase of interleukin-1β and C-reactive protein secretion. As a result of years of working in high-temperature conditions, inflammation can lead to subsequent diseases in workers. To protect their health from this occupational hazard, additional safeguards are needed. Our recommendations could also be applied to overly hot work environments that may cause heat stress in workers.

Larger pollen loads increase risk of heat stress in foraging bumblebees.

Global declines in bumblebee populations are linked to climate change, but specific mechanisms imposing thermal stress on these species are poorly known. Here we examine the potential for heat stress in workers foraging for pollen, an essential resource for colony development. Laboratory studies have shown that pollen foraging causes increased thoracic temperatures (Tth) in bees, but this effect has not been examined in bumblebees nor in real-world foraging situations. We examine the effects of increasing pollen load size on Tth of Bombus impatiens workers in the field while accounting for body size and microclimate. We found that Tth increased by 0.07°C for every milligram of pollen carried (p = 0.007), resulting in a 2°C increase across the observed range of pollen load sizes. Bees carrying pollen were predicted to have a Tth 1.7-2.2°C hotter than those without pollen, suggesting that under certain conditions, pollen loads could cause B. impatiens workers to heat from a safe Tth to one within the range of their critical thermal limits that we measured (41.3°C to 48.4°C). Bumblebees likely adopt behavioural or physiological strategies to counteract the thermal stress induced by pollen transport, and these may limit their foraging opportunities as environmental temperatures continue to increase.

Improvement of Louvers and Openings of Factory Building to Remove Heat through Natural Wind

Heat accumulated in the factory building not only causes heat stress in workers but also reducesproductivity. This research is aimed at improving the opening and the louvers in consistent with the natural windand heat sources in buildings to remove heat. The study includes the measurement of the factory surfacetemperatures, air temperature and machinery heat and inputting into the model in ANSYS FLUENT 13.0, acomputational fluid dynamic program. The simulated results show the flow patterns and temperature of the airin the building. Simulation results show that the opening positions, angle of louvers and roof form bring warmair out of the building in two parts: heat attached to roof and heat in the working area. In addition, propercombination of opening position, louvers and roof form helps prevent the hot air from the top and increasingthe rate of heat flow out of work. The results show that the improvement of louvers increases wall openingfrom 10% to 30% and can reduce the working temperature down close to the ambient air of 32.5°C. Installationof opening on the roof can reduce the roof temperature by 10-12°C, resulting in preventing of radiative heattransfer from roof to working area.

Active Textile Glove for Cooling and Personal Protection

Conventional gloves partially insulate against heat transfer from a hot external environment. They also prevent metabolic heat generated by the human body from escaping. Thus, gloves are a source of heat buildup and heat stress in workers. Heat stress can lead to hyperthermia. Described herein is a glove that cools using a carbon nanotube (CNT) fabric micro-liner and forced convection from a fan. A cold sink is assumed to be located in the glove to cool the convection air. This glove is called an active textile glove. CNT fabric has high thermal conductivity in the plane of the fabric, low thermal conductivity through its thickness, and a large surface area for convection cooling. Thus, the active textile glove can transfer heat from the hand to cooler air in the environment. This paper simulates the performance of a CNT-cooled glove using simple theoretical heat transfer models. Cooling was also demonstrated by testing the glove using a hot plate. Forced convection was found to provide the greatest cooling effect, with it working in synergy with the CNT fabric which aids in spreading heat. CNT fabric also acts as a shield from environmental dangers. The fabric is flame resistant, attenuates radio frequency waves, and prevents smoke particles and toxic chemicals from entering the glove. Testing illustrates the shielding properties of CNT fabric.

Worker heat stress prevention and work metabolism estimation: comparing two assessment methods of the heart rate thermal component

The heart rate thermal component () can increase with body heat accumulation and lead to work metabolism (WM) overestimation. We used two methods (VOGT and KAMP) to assess of 35 forest workers throughout their work shifts, then compared at work and at rest using limits of agreement (LoA). Next, for a subsample of 20 forest workers, we produced corrected WM estimates from and compared them to measured WM. Although both methods produced significantly different time-related profiles, they yielded comparable average thermal cardiac reactivity (VOGT: 24.8 bpm °C−1; KAMP: 24.5 bpm °C−1), average (LoA: 0.7 ± 11.2 bpm) and average WM estimates (LoA: 0.2 ± 3.4 ml O2 kg−1min−1 for VOGT, and 0.0 ± 5.4 ml O2 kg−1min−1 for KAMP). Both methods are suitable to assess heat stress through and improve WM estimation.Practitioner summary: We compared two methods for assessing the heart rate thermal component (), which is needed to produce a corrected HR profile for estimating work metabolism (WM). Both methods yielded similar estimates that allowed accurate estimations of heat stress and WM at the group level, but they were imprecise at the individual level.Abbreviations: AIC: akaike information criterion; bpm: beats per minute; CI: confidence intervals; CV: coefficient of variation in %; CV drift: cardiovascular drift; ΔHRT: the heart rate thermal component in bpm; ΔHRT: the heart rate thermal component in bpm; ΔΔHRT: variation in the heart rate thermal component in bpm; ΔTC: variation in core body temperature in °C; HR: heart rate in bpm; HRmax: maximal heart rate in bpm; Icl: cloting insulation in clo; KAMP: Kampmann et al. (2001) method to determe ΔHRT; LoA: Limits of Agreement; PMV-PPD: the Predicted Mean Vote and Predicted Percentage Dissatisfied; PHS: Predicted Heat Strain model; RCM: random coefficients model; SD: standard deviation; TC: core body temperature in °C; TCR: thermal cardiac reactivity in bpm °C−1; τΔHRT: rate of change in the heart rate thermal component in bpm min−1; τTC: rate of change in core body temperature in °C min−1; tα,n-1: Student’s t statistic with level of confidence alpha and n−1 degrees of freedom; TWL: Thermal Work Limit model; : oxygen consumption in ml O2 kg−1 min−1; max: maximal oxygen consumption in ml O2 kg−1 min−1; VOGT: Vogt et al. (1973) method to determine ΔHRT; WBGT: Wet-Bulb Globe Temperature in °C; WM: work metabolism

Evaluation of Occupational Exposure to Heat Stress and Physiological Responses of Workers in the Rolling Industry

Background and Objective: Many indices are used to assess occupational heat stress at the work environments. The aim of this study was to evaluate heat stress using Wet Bulb Globe Temperature (WBGT) index and Discomfort Index (DI), and by measuring physiological responses in the workers of the rolling industry and comparing the appropriateness of these indices for measuring heat stress. Methods: This cross-sectional study was carried out on 90 healthy workers of a rolling industry in eastern Tehran in 2017. Physiological parameters of core body temperature (Tcr) and Heart Rate (HR) were measured during the working shift according to ISO9886 standard. At the same time, environmental variables such as the natural wet temperature (Tnw), dry temperature (Td) and globe temperature (Tg) were measured and recorded at the workstations. Then, the DI and the WBGT indices were calculated using the related formulae. Data were analyzed using SPSS v. 21, t-test and Pearson correlation coefficient. Results: The mean heat stress indices were significantly higher in working conditions than resting conditions, and there was a significant difference between the physiological parameters of Tcr and HR in resting and working conditions (P<0.001). According to the screening criteria of DI, 43.3% of the workers were exposed to the moderate level and 56.7% to the severe level of heat stress. There was a significant difference between the mean WBGT and the Threshold limit values (t= 4.903, P<0.001). Pearson correlation test showed that there was a significant and direct linear relationship between the WBGT and the physiological parameters of Tcr and HR (r=0.317, P=0.002; r=0.434, P<0.001, respectively). The DI index had a significant and direct linear relationship with HR; (r=0.229, P=0.03). Conclusion: The results showed that WBGT is a more appropriate index for evaluating the heat stress of workers in the rolling industry. High heat stress levels at the workstations along with heavy physical activity are health risks for workers in this industry; therefore, interventions must be undertaken to reduce exposure.

Investigation on heat stress of construction workers in summer in Chongqing, China

The heat stress of workers at construction sites in Chongqing, China, was studied in this paper. The investigation included measurement of environmental parameters, measurement of physiological parameters, questionnaire survey and tracking record of their self-regulation of the behaviour. Scaffolder, carpenter, porter, plasterer and handymen were taken as the main research subjects. Five subjects were selected daily to conduct a questionnaire survey and to measure their physiological parameters, 60 construction workers were investigated. The results show that in sizzling summer, the average effective Wet Bulb Globe Temperature (WBGTeff) is 35.8 ° C. Under these circumstances, workers are in a poor working environment based on some Chinese and international standards. During the experiment, the researchers recorded the work behaviour and self-regulation of workers. It is found that the average heart rate of workers with different job is significantly different, and the average metabolic rate of handymen is significantly lower than that of piling rig workers. Different type of workers should be protected by different protection rules to avoid suffering heat injury.

Using trunk posture to monitor heat strain at work

This study aimed to determine if trunk posture during walking is related to increases in rectal temperature (Tre). 24 males treadmill walked in one of four conditions (1): 30 min at 3.0 mph and 0% grade, 20 °C and 50% relative humidity (RH), wearing healthcare worker (HCW) PPE; (2): 30 min at 3.0 mph and 0% grade, 27.5 °C and 60% RH, HCW PPE; (3): 30 min at 3.0 mph and 0% grade, 32.5 °C and 70% RH, HCW PPE; and (4): 40 min at 40% VO2max, 30 °C and 70% RH, wearing firefighter PPE. Trunk posture (Zephyr BioHarness 3) and Tre were measured continuously. Tre was positively related to trunk posture, controlling for covariates (B = 3.49, p < .001). BMI and age moderated this relationship (Tre×age, B = 0.76, p < .001; Tre*BMI, B = −1.85, p < .001). Trunk posture measurement may be useful in monitoring fall potential and magnitude of heat stress of workers in hot environments.Practitioner Summary: Occupational hyperthermia increases worker risk for heat illness and injury but is difficult to monitor in the field. This investigation shows that trunk posture is independently and positively related to core temperature. Non-invasive measurement or visual inspection of trunk posture could provide novel insight on individual heat strain level.

Farmworker Vulnerability to Heat Hazards: A Conceptual Framework.

To review factors that impact the effect of hot environments on the human body in order to develop a conceptual model of human biological response. The organizing concept for the model development was the multilevel integration of three major factors, exposure to heat, sensitivity and adaptive capacity, and the heat stress response. Exposure of a vulnerable occupational group was used to illustrate the components of the model. Components of this framework include the hazard (environmental heat stress), vulnerability factors (workplace exposure, sensitivity and adaptive capacity), and the heat stress response. The combination of the vulnerability factors of workplace exposure (work intensity, duration), sensitivity (age, gender, etc.), and adaptive capacity (hydration, clothing, work hygiene) mediate a worker's heat stress response to the hazard. A worker's heat stress response can be classified as progressing towards two outcomes: physiologic equilibrium or physiologic disequilibrium. This framework provides a starting point for the design and development of studies of heat-related illness (HRI) in farmworker and other vulnerable populations exposed to rising global temperatures. Identification of vulnerability factors to HRI, informs research designs which will lead to the development of public health interventions.

The efficacy of radiant heat controls on workers' heat stress around the blast furnace of a steel industry.

Workers' exposure to excessive heat in molten industries is mainly due to radiant heat from hot sources. The aim of this study was to evaluate the efficacy of radiant heat controls on workers heat stress around a typical blast furnace. Two main interventions were applied for reducing radiant heat around the blast furnace of a steel industry located in western Iran. These included using a heat absorbing system in the furnace body and installing reflective aluminum barrier in the main workstation. Heat stress indexes were measured before and after each intervention using the digital WBGT-meter. The results showed MRT and WBGT indexes decreased by 20 °C and 3.9 °C, respectively after using heat absorbing system and also decreased by 18.6 °C and 2.5 °C, respectively after installing a reflective barrier. These indexes decrease by 26.5 °C and 5.2 °C, respectively due to the simultaneous application of the two interventions which were statistically significant (p < 0.001). The core body temperature of workers decreased by 2.6 °C after the application of interventions which was also significant (p < 0.05). The results confirmed heat control at source can be considered as a first solution for reducing radiant heat of blast furnaces. However, the simultaneous application of interventions could noticeably reduce worker heat stress. The results provide reliable information in order to implement the effective heat controls in typical hot steel industries.

Screening for Heat Stress in Workers and Athletes

Heat-related illnesses lead to almost 6000 hospital visits per year, or two emergency department visits per 100,000 visits. Heat-related illnesses are most high among men (72%) aged 15 to 19 years and are most often associated with athletic activities (1). Global climate change will continue to have an impact on heat stress in people, on animal survival, and on food availability. The World Health Organization has estimated that over the past 30 years, 150,000 lives have been lost annually due to global heat waves and climate change (2). Weather changes have a great impact on athletes and workers by slowing efficiency and decreasing productivity (3, 4). When heat waves occur, overall mortality is also affected among the old and the young, due to their increased risk of dying from cardiovascular, respiratory, cerebrovascular, and some cardiovascular diseases, such as ischemic heart disease, heart failure, and myocardial infarction (3). Despite increasing temperatures and environmental levels of carbon dioxide, one third of metropolitan areas do not have heat stress response plans (5). Cases of heat stress are handled on a case-by-case basis rather than by being addressed collectively as a public health concern. The National Institute for Occupational Safety and Health initiated heat stress criteria in 1986 and amended them in 2008 regarding worker heat stress safety (6). Few people are aware of these criteria, of the risk factors associated with a predisposition to heat stress, or of the signs or symptoms to look for that represent risk factors for heat stress. The rules and standards proposed by the Occupational Safety and Health Administration for workplace heat stress are recommendations and still not enforceable (7). Screening for heat stress susceptibility in workers and athletes is an issue in need of public health criteria with enforceable rules based on evidence-based research. Screening for heat stress risk factors should consider physical demand level; cardiovascular, pulmonary, and endocrine status; previous history of heat stress; age; diseases; and medications including illegal drug use. Such screening should be part of the recruitment of any person expected to work or play in extremely hot environmental conditions. Older people are at increased risk for cardiovascular and thermoregulatory instability. The aging American workforce, undiagnosed disease, poor hydration while working or playing, and global warming are all factors that contribute to the need to screen workers and athletes for the risk of heat stress (8). This article first reviews some physiological aspects of temperature regulation and then provides a formula for heat stress testing, discusses guidelines for screening, and reviews accommodations for those susceptible to heat stress.

The evaluation of heat stress through monitoring environmental factors and physiological responses in melting and casting industries workers

Aims: Evaluation of heat stress in workers exposed to hot/dry conditions of melting and casting industry is imperative for management of heat stress. This study aims to compare results of heat strain evaluation by monitoring environmental factors and physiological responses. Materials and Methods: This is a cross-sectional study that was conducted on 51 workers of a large melting and casting company in 2010. Wet Bulb Globe Temperature (WBGT) index, heart rate and ear canal temperature were measured by WBGT meter, heart rate monitor and personal heat stress monitor, respectively. Physical activity intensity was assessed based on the ratings of perceived exertion (RPE). Data were analyzed using descriptive statistics and Pearson correlation test. Results: WBGT index in 64.7% of workstations exceeded 30°C and in 41.2% was over 32°C. The value of WBGT index in 69% of work stations exceeded the threshold limit of the ACGIH standard. The physiological strain index (PSI) in 31% of worker was higher than 5, although its mean measured at 3.8 (1.8). Increase in the ear canal temperature in 64.7% of cases (33 persons) was over 1°C. Correlation between WBGT index with ear canal temperature and PSI index, adjusted body mass index and age, was 0.67 and 0.69 (P < 0.0001).Conclusion: In hot/dry conditions of melting and casting processes, despite moderate correlation between WBGT index with ear canal temperature and PSI index, work-rest cycles of WBGT index is not applicable for many of the workstations. Therefore, heat stress evaluation based on physiological variables probably has higher validity and is more appropriate.

Effects of Local Cooling on Heat Strain in the Hot Environment -On the Trunk Region-

This study was to determine the effect of cooling part of the trunk without harm for the health. The results provide basic data for the development of clothing which could increase work efficiency and reduce body strain in hot environment. Eight males took part in the study. The experiment was conducted in a climate-chamber controlled with 37±1℃, 50±5%R.H. The trunk was divided into six areas to be cooled: head, neck, chest, abdomen, the upper back, the lower back. According to preceding studies, permissible safety cooling limits of skin temperature, of each part of the trunk for four hours cooling were 25℃ on the head, 20℃ on the neck, 27℃ on the chest, 25℃ on the abdomen, 20℃ on the upper back, 20℃ on the lower back. So cooling temperatures of each region set up temperatures above mentioned. In conclusion, the head, the neck and the upper back cooling could reduce sweating amount, rectal temperature and heart rates and reduce the heat stress of workers exposing in the hot environment by decreased subjective sensations of heat and comfort. Thus, it was concluded that effectiveness of cooling among the trunk was best on the head and the neck.

Strenuous tasks in a hot climate – a case study

Studies of worker heat stress and strain in various countries have found that heat exposure is often likely to exceed the upper threshold limit of international standards. Heat strain data such as oral temperature, recovery heart rate, average heart rate and other work‐related information were investigated to study the impact of strenuous tasks in a hot climate. The study attempted to establish relationships between exposure to heat and heat strain data which could be used as the basis of ergonomic intervention and low‐cost solutions to the avoidance or mitigation of occupational risks.

Heat stress and strain in an aluminum smelter.

Studies of worker heat stress and strain in aluminum smelters have found that heat exposure likely to exceed the American Conference of Governmental Industrial Hygienists' threshold limit value (TLV) and that the dose-response relationship between heat stress and strain was weak. A heat stress model based on climatic data and a task analysis indicated exposures to heat stress in excess of the TLV during the July/August study period. To study the impact of working above the TLV, heat strain data (i.e., oral temperature, recovery heart rate, average heart rate) were collected. Recovery heart rates indicated high strain most of the time, and oral temperatures after peak demands were above the no-strain threshold of 37.5 degrees C about a quarter of the time, indicating that heat stress had an effect. About 95% of the readings were below 38.0 degrees C, the acute oral temperature threshold for a safe exposure. Average heart rates over 6- and 12-hour intervals were generally below acceptable limits of 120 and 110 bpm, respectively. Oral temperature and average heart rates indicated good control of heat stress exposures. Because recovery heart rates were high, some employees were working near their individual limits. The dose-response relationship for recovery heart rate and oral temperature were examined against the level of heat stress above the TLV. There was no relationship between oral temperature and heat stress level. There was an apparent trend toward higher recovery heart rates with heat stress. The lack of a dose-response relationship may be explained by brief periods of very high wet bulb globe temperatures that drove the time-weighted average up out of proportion to the physiological response.

PHYSIOLOGICAL EVALUATION OF LIQUID-BARRIER, VAPOR-PERMEABLE PROTECTIVE CLOTHING ENSEMBLES FOR WORK IN HOT ENVIRONMENTS

Work clothes using fabrics with vapor-transmitting characteristics are in limited use in various industrial applications, and there is a growing interest in their purported ability to help reduce heat stress. This study was performed to compare two vapor-transmitting ensembles with other clothing ensembles previously tested. The evaluation was based on an established experimental protocol that determines the critical values of air temperature and water-vapor pressure so that an individual maintains thermal balance, while controlling other factors that contribute to worker heat stress (e.g., air motion and metabolism). There were no differences between the two vapor-transmitting garments in their effects on worker heat stress. When compared to the results of other studies, the two vapor-transmitting garments had critical environmental characteristics similar to two layers of cotton coveralls and they performed better from a heat stress standpoint than a disposable vapor-barrier suit worn over cloth coveralls.