Calculating Workplace WBGT from Meteorological Data: A Tool for Climate Change Assessment

The WBGT heat stress index has been well tested under a variety of climatic conditions and quantitative links have been established between WBGT and the work-rest cycles needed to prevent heat stress effects at the workplace. While there are more specific methods based on individual physiological measurements to determine heat strain in an individual worker, the WBGT index is used in international and national standards to specify workplace heat stress risks. In order to assess time trends of occupational heat exposure at population level, weather station records or climate modelling are the most widely available data sources. The prescribed method to measure WBGT requires special equipment which is not used at weather stations. We compared published methods to calculate outdoor and indoor WBGT from standard climate data, such as air temperature, dew point temperature, wind speed and solar radiation. Specific criteria for recommending a method were developed and original measurements were used to evaluate the different methods. We recommend the method of Liljegren et al. (2008) for calculating outdoor WBGT and the method by Bernard et al. (1999) for indoor WBGT when estimating climate change impacts on occupational heat stress at a population level.     

Comparison of heat stress measuring techniques in a steel mill

Three heat stress measurement devices, currently used to assess heat exposure in the workplace, were compared in indoor and outdoor environments at a steel mill in Orem, Utah, during the month of July, 1982. Sixty sets of environmental data from a total of fourteen different test locations were collected and analyzed. Significance tests, linear regression equations and correlation coefficients were calculated to determine comparability and relationships between standard WBGT Index and Botsball (WGT) and also between standard WBGT Index and an electronic WBGT Index Meter. The results of the significance testing between the standard WBGT, Botsball, and electronically generated WBGT showed that the electronically generated WBGT means were statistically much closer to the standard WBGT values than were the Botsball (WGT) results. The statistical analysis performed shows that a high correlation of variation exists between the standard WBGT and both the Botsball and the electronically generated WBGT.     

Applicability of Universal Thermal Climate Index (UTCI) in occupational heat stress assessment: a case study in brick industries

The present study aimed to investigate the applicability of Universal Thermal Climate Index (UTCI) as an innovative and science-based index in public health researches, in occupational heat stress assessment. All indoor and outdoor workers (200 people) of Brick industries of Shahroud, Iran participated in the research. First, the environmental variables such as air temperature, wet-bulb temperature, globe temperature, air velocity and relative humidity were measured; then UTCI and WBGT (wet-bulb globe temperature) indices were calculated. Simultaneously, physiological parameters including systolic and diastolic blood pressure, oral temperature, skin temperature, tympanic temperature and heart rate of workers were measured. UTCI and WBGT indices were 34.2 ± 2°C, 21.8 ± 1.8°C in the outdoor environments and 38.1 ± 4.4°C, 24.7 ± 3.3°C at the indoor environments, respectively. There were the weak inverse relationships between UTCI and WBGT indices at the outdoor environments and physiological responses such as systolic blood pressure, and diastolic blood pressure. However, there were no similar results for indoor environments. The significant relationships were found between UTCI and WBGT at both indoor and outdoor environments. Both UTCI and WBGT indices are suitable for assessing the occupational heat stress. Although, UTCI index seems more appropriate for heat stress assessment in the environments with low humidity and air velocity.     

The prediction of temperatures and heat stress limits in the workplace with natural ventilation

This paper presents a simple procedure for using the climatic factors reported by weather bureaus to predict levels of heat stress and conditions of risk in the workplace. For an aluminum reduction plant with natural ventilation, the study showed that the air temperature inside followed the same pattern of annual changes as the normal maximum ambient temperature outside the building. The Wet Bulb Globe Temperature (WBGT) was correlated significantly with air temperature (ta). With limited measurements, WBGT was predicted for the entire year at different locations in the shop.     

Heat stress in rice vermicelli manufacturing factories

Objective: This study provides an assessment of heat stress in indoor rice vermicelli manufacturing factories.

Methods: Worker interviews and heat stress assessments were conducted in food manufacturing factories in Singapore. The Wet Bulb Globe Temperature (WBGT) and Heat Stress Index (HSI) were used as heat stress indicators.

Results: The highest WBGT and HSI levels recorded in the rice vermicelli manufacturing factories were 36.68°C and 3777 in the drying and steaming process respectively. These levels were above the recommended permissible HSI and WBGT action limit for heat exposure and considered to be high risk.

Conclusion: Workers in indoor rice vermicelli manufacturing factories can be exposed to heat stress, and the current measures in place may not be sufficient to protect workers against heat stress injuries. Preventive measures such as engineering controls and heat acclimatization programs are important.     

Validation of a Temperature Prediction Model for Heat Deaths in Undocumented Border Crossers

Heat exposure is a leading cause of death in undocumented border crossers along the Arizona–Mexico border. We performed a validation study of a weather prediction model that predicts the probability of heat related deaths among undocumented border crossers. We analyzed a medical examiner registry cohort of undocumented border crosser heat- related deaths from January 1, 2002 to August 31, 2009 and used logistic regression to model the probability of one or more heat deaths on a given day using daily high temperature (DHT) as the predictor. At a critical threshold DHT of 40 °C, the probability of at least one heat death was 50 %. The probability of a heat death along the Arizona–Mexico border for suspected undocumented border crossers is strongly associated with ambient temperature. These results can be used in prevention and response efforts to assess the daily risk of deaths among undocumented border crossers in the region.     

新标准下某单位高温测量结果分析

目的通过对某用人单位作业场所高温的测量与分析,确定高温作业岗位,加强高温作业场所防护工作,保护劳动者身体健康。方法采用职业卫生学调查法、现场测量法、分类查表法进行测量分析。结果该用人单位油漆车间挂钩岗位湿球黑球温度（WBGT）指数平均值为31．3℃,摘钩岗位WBGT指数平均值为30．8℃,甩漆浸漆岗位WBGT指数平均值为30．9℃,喷漆岗位WBGT指数平均值为30．4℃。结论该用人单位油漆车间挂钩、摘钩、甩漆浸漆、喷漆岗位为高温作业岗位。这些岗位的平均WBGT指数均超过WBGT限值。应采取相应措施对高温作业工人进行防护,防止中暑发生。     

Heat stress standard for hot work environments in Japan

Threshold limit values (TLVs) are intended to protect workers from the severest effects of thermal stress and to establish the exposures to heat in working conditions. Earlier, acute heat strokes often occurred as a result of working in hot environments in Japan. However, acute heat strokes recently sometimes occurred in outdoor work environments such as industrial constructions and agriculture. Seasonal variations in weather are significant and the climatic conditions vary. The criteria are mainly set for working in mines, factories, and so on. WBGT is a useful evaluation index for hot environments; however, it is not commonly used for work practices. WBGT could be calculated and should be commonly used as a standard during summer. Japan mainly has a very hot and humid climate during summer. With regard to the thermal standard for offices, humidity also creates a problem in the indoor thermal conditions. Therefore, it is better to decide the TLVs of the thermal conditions according to seasons and activity levels. Inadequate thermal stress may cause discomfort and adversely affect the performance, safety, and harm to health. Further, thermal factors in the work environment must be measured and evaluated under light workload conditions like desk work for safety and work efficiency.     

“I Think the Temperature was 110 Degrees!”: Work Safety Discussions Among Hispanic Farmworkers

Heat-related illness (HRI) among migrant and seasonal farmworkers is an occupational risk addressed through varying mitigation strategies by individual workers and supervisors. The purpose of this pilot study was to describe farmworkers’ experience with HRI prevention strategies and assess HRI information seeking preferences, especially the feasibility of using mobile phone apps to access this information. Five focus groups were administered to Hispanic farmworkers in South Carolina. Questions included the following topics: health information seeking preferences; farmworkers’ perceptions of occupational risks; coping strategies; past experiences with HRIs; water, rest, and shade practices; access to health care; and any employer-provided training received. There was consensus across the groups that the workers at highest risk for HRIs were either inexperienced or new workers in the fields. Farmworkers ascribed responsibility for one’s well-being while working in the heat more as an individual factor than as an employer’s responsibility. Farmworkers received training on the OSHA Heat Safety Tool app and provided positive feedback about the educational content and temperature information warnings. These findings suggest the potential for supervisors to take a more active role in heat safety education using mobile technology.     

Preventing heat illness in the anticipated hot climate of the Tokyo 2020 Summer Olympic Games

Amid the effects of global warming, Tokyo has become an increasingly hot city, especially during the summertime. To prepare for the upcoming 2020 Summer Olympics and Paralympics in Tokyo, all participants, including the athletes, staff, and spectators, will need to familiarize themselves with Tokyo’s hot and humid summer conditions. This paper uses the wet-bulb globe temperature (WBGT) index, which estimates the risk of heat illness, to compare climate conditions of sports events in Tokyo with the conditions of the past three Summer Olympics (held in Rio de Janeiro, London, and Beijing) and to subsequently detail the need for establishing appropriate countermeasures. We compared WBGT results from the past three Summer Olympics with the same time periods in Tokyo during 2016. There was almost no time zone where a low risk of heat illness could be expected during the time frame of the upcoming 2020 Tokyo Olympics. We also found that Tokyo had a higher WBGT than any of those previous host cities and is poorly suited for outdoor sporting events. Combined efforts by the official organizers, government, various related organizations, and the participants will be necessary to deal with these challenging conditions and to allow athletes to perform their best, as well as to prevent heat illnesses among staff and spectators. The sporting committees, as well as the Olympic organizing committee, should consider WBGT measurements in determining the venues and timing of the events to better avoid heat illness and facilitate maximum athletic performance.     

Body heat storage during intermittent work in hot-dry and warm-wet environments

We examined heat balance using an American Conference of Governmental Industrial Hygienists threshold limit value allocated exercise protocol in hot-dry (HD; 46 °C, 10% relative humidity (RH)) and warm-wet (WW; 33 °C, 60% RH) environments of equivalent WBGT (29 °C) for different clothing ensembles. Whole-body heat exchange and changes in body heat content (ΔH(b)) were measured using simultaneous direct whole-body and indirect calorimetry. Eight males performed six 15-min cycling periods at a constant rate of metabolic heat production (360 W) interspersed by 5-min rest periods for six experimental trials: HD and WW environments for a seminude control (CON), modified work uniform (MWU, moisture permeable top and work pants), and standard work uniform (SWU, work coveralls and cotton undergarments). Whole-body evaporative and dry heat exchange, rectal temperature (T(re)), and heart rate were measured continuously. The cumulative ΔH(b) during the 2 h intermittent exercise protocol was similar between HD and WW environments for each of the clothing ensembles (CON, 387 ± 55 vs. 435 ± 49 kJ; MWU, 485 ± 58 vs. 531 ± 61 kJ; SWU, 585 ± 74 vs. 660 ± 54 kJ, respectively). Similarly, no differences in T(re) (CON, 37.67 ± 0.07 vs. 37.48 ± 0.08 °C; MWU, 37.73 ± 0.08 vs. 37.53 ± 0.09 °C; SWU, 38.01 ± 0.09 vs. 37.94 ± 0.05 °C) or heat rate (CON, 93 ± 3 vs. 84 ± 3 beats·min?1; MWU, 102 ± 5 vs. 95 ± 9 beats·min?1; SWU, 119 ± 8 vs. 110 ± 9 beats·min?1) were observed at the end of the 2 h intermittent exercise protocol in HD vs. WW environments, respectively. We showed similar levels of thermal and cardiovascular strain for intermittent work performed in high heat stress conditions of varying environmental conditions but similar WBGT.     

Criteria for assessing severely hot environments: from the WBGT index to the PHS (predicted heat strain) model

BACKGROUND: The present study deals with the main methods for assessment of hot environments: i.e., WBGT, SWreq and PHS. It is stressed how the WBGT index, which is strictly empirical, although a very practical tool for the assessment of the hot environments, can only be used for a rough evaluation of heat stress, and especially for a not very high metabolic rate (M<175 W/m2). On the contrary, the SWreq method, which is based on both subject-environment heat exchange and the effect of clothing, allows a better assessment of the work situation with a general reduction of the exposure limits with respect to WBGT, especially in non-uniform environments (ta not equal to tr). However, it should be noted that application of SWreq is required by the ISO standard 7243 when the WBGT limit values are exceeded. METHODS: In this study interest was extensively focused on the "Predicted Heat Strain" method, highlighting via a special software the differences in heat stress assessment related to this new approach, which will be adopted by the ISO in the next revision of standard 7933. RESULTS: The PHS method, unlike SWreq, allows the prediction of the time-response of the main physiological variables of interest (i.e., skin temperature, core temperature and sweat rate). Moreover thanks to better modelling of heat exchanges, the PHS method allows account to be taken of both movement and clothing effects, resulting in even more reduced exposure.     

Heat strain and heat stress for workers wearing protective suits at a hazardous waste site

In order to evaluate the effects of heat stress when full body protective suits are worn, heart rates, oral temperatures and environmental parameters were measured for five unacclimatized male workers (25-33 years of age) who performed sampling activities during hazardous waste clean-up operations. The protective ensembles included laminated PVC-Tyvec chemical resistant hood suits with rubber boots, gloves full facepiece dual cartridge respirators and hard hats. For comparison, measurements also were performed when the men worked at a similar level of activity while they wore ordinary work clothes. A comparison of the heart rates for the men working with and without suits indicated that wearing the suits imposed a heat stress equivalent to adding 6 degrees to 11 degrees C (11 degrees to 20 degrees F) to the ambient WBGT index. A similar result was obtained by calculating the WBGT in the microclimate inside the suits and comparing it to the ambient WBGT. These results indicate the following: 1) there exists a significant risk of heat injury during hazardous waste work when full body protective clothing is worn, and 2) threshold limit values for heat stress established by the ACGIH must be lowered substantially before extending them to cover workers under these conditions.     

Fluid replacement advice during work in fully encapsulated impermeable chemical protective suits

A major concern for responders to hazardous materials (HazMat) incidents is the heat strain that is caused by fully encapsulated impermeable chemical protective suits. In a research project, funded by the US Department of Defense, the thermal strain experienced when wearing these suits was studied. One particular area of interest was the fluid loss of responders during work in these suits as dehydration may be an additional health concern to the heat strain. 17 City of Raleigh firemen and 24 students were tested at two different labs. Subjects between the ages of 25 and 51 were used for human subject trials in a protocol approved by the local ethical committee. Six different Level A HazMat suits were evaluated in three climates: moderate (24°C, 50% RH, 20°C WBGT), warm-wet (32°C, 60% RH, 30°C WBGT), and hot-dry (45°C, 20% RH, 37°C WBGT, 200 W/m² radiant load) and at three walking speeds: 2.5 km/hr, 4 km/hr, and 5.5 km/hr. 4 km/hr was tested in all three climates and the other two walking speeds were tested in the moderate climate. Weight loss data was collected to determine fluid loss during these experiments. Working time ranged from as low as 20 min in the hot-dry condition to 60 min (the maximum) in the moderate climate, especially common at the lowest walking speed. The overall results from all experiments showed that fluid loss ranged from 0.2–2.2 L during these exposures, with the average fluid loss being 0.8 L, with 56% of the data between 0.5 L and 1 L of fluid loss. Further analysis showed that a suggestion of drinking 0.7 Liter per hour would safely hydrate over 50% of responders after one work-rest cycle. Applying this fluid volume over three work-rest cycles only put 11% of responders at risk of hypohydration vs. the 57% at risk with no fluid intake.     

The impact of extremely high temperatures on mortality and mortality cost

The aim of this study was to determine the temperature threshold that triggers an increase in heat-induced mortality in Zaragoza, Spain to determine the impact of extreme heat on mortality and in-hospital cost. A longitudinal ecological study was conducted according to an autoregressive integrated moving average model of a time series for daily deaths and to determine the relative risk of mortality for each degree that the temperature threshold was exceeded. Mortality showed a statistically significant increase when the daily maximum temperature exceeded 38?°C. A Relative Risk was 1.28 with a 95?% confidence interval (95?%CI:1.08–1.57) This threshold temperature didn’t change over time. A total of 107 (95?%CI:42–173) heat-attributable deaths were estimated for the period 2002–2006, and the in-hospital estimated cost of these deaths reach € 426,087(95?%CI.€167,249–€688,907). The articulation of preventive measures to minimize the impact of extreme heat on human health is necessary because of the mortality–temperature relationship.     

Does hot weather affect work-related injury? A case-crossover study in Guangzhou,China

Background

Despite increasing concerns about the health effects of climate change, the extent to which workers are affected by hot weather is not well documented. This study aims to investigate the association between high temperatures and work-related injuries using data from a large subtropical city in China.

大覆盖面积囊式抗荷服的热负荷

目的研究2种飞行员大覆盖面积囊式抗荷服及其配套装备的热负荷，为确定新型抗荷服囊覆盖下肢体表面积提供生理依据。方法采用暖体假人测定2组装备热阻值（It）；6名受试者分别配穿囊覆盖下肢体表面积80％组和60％组装备，在26℃、35℃和40℃3种温度环境中90min，测量受试者的心率、皮肤温度、核心温度和出汗量，利用综合热应激指数（CIHS）评价受试者的热应激程度，并测量装备蒸发散热指数（im）。结果80％组和60％组装备热阻值（It）分别为1．815clo和1．740clo。蒸发散热指数（im）分别为0．39±0．04和0．41±0．04，差异无显著性。受试者配穿80％组和60％组服装．在35cc时综合热应激指数（CIHS）分别为4．51±0．51和3．92±0．51，前者为中度热应激，而后者为轻度热应激，差异有显著性（P〈0．05）；在40℃时，综合热应激指数（CIHS）分别为8．79±0．73和8．14±0．91，均属重度热应激，差异有显著性（P〈0．05）。结论当环境温度较高时，人体配穿80％组装备时会遭受更加严重的热负荷。     

CASH--an innovative approach to sustainable OSH improvement at workplace

Occupational health department of a large private enterprise located in India launched Project CASH--Change Agents for Safety and Health, at manufacturing units of the enterprise to bring about a positive change in work environment and improvement in work practices to reduce occupational health risk. Multidisciplinary teams of change agents were constituted and were given intensive training inputs. Reduction in exposure to noise, dust and heat stress were identified as specific objectives after a baseline survey of the work environment. Occupational safety and health knowledge and training was imparted to all field personnel to improve their work practices and attitudes. The focus of the actions was on engineering control measures and process engineering changes necessary for workplace improvement. Noise levels were reduced by an average of more than 9dBA in most of the top ten high noise locations. Out of two locations identified for dust exposure, one was fully eliminated and dust levels at other location were significantly reduced. Heat stress was reduced in all three identified locations with an average reduction of more than 3 degrees C in WBGT levels. Thus, final evaluation of workplace environments revealed significant reduction in exposure to all identified agents, viz noise, dust and heat fulfilling the project objectives. Educating and empowering the team led to reduction of occupational health risks in the work environment. There was positive attitudinal and behavioural change in safety and occupational health awareness & practices among employees. The monetary savings resulting from improvements far outweighed the investments. Success of this pilot project was followed up with further similar projects and their number has grown in geometric proportion for the last three years indicating the sustainability of the project.     

Ischaemic heart disease mortality and weather temperature in Barcelona, Spain

Background: Association between ischaemic heart disease (IHD)mortality and extreme values of weather temperature has beenthe focus of many previous studies. To what extent moderatechanges in temperature also influence IHD mortality in milderregions, where either low temperatures or heat waves are exceptional,has been less Investigated. To further contribute to these issueswe have investigated the association between weather temperatureand IHD in Barcelona, Spain. Methods: A transfer function modelwas specified. The dependent variable was the daily time seriesof IHD while, weather temperature, relative humidity and airpollutants were the covariates. We also controlled for influenzaepidemics and annual seasonality. In order to relax the restrictiveassumptions (functional form and normality) imposed by the transferfunction, this was modelled non-parametrically. The influenceof unusual periods and outliers of weather temperature and humiditywas also assessed. Results: A non-linear relationship betweenweather temperature and IHD existed. Our results suggested atemperature threshold (estimated in 21.06°C) in the relationshipbetween IHD and weather temperature. The estimated value ofthe threshold was higher (23°C) for very humid days (relativehumidity above 85%). The risk of an IHD death increased approximately2.4% with every 1°C drop of temperature below 4.7°Cand approximately 4% with every 1°C rise above 25°C.Conclusion: Our findings corroborated that not only the thresholdbut also the magnitude of the association presents a differentrange depending on the latitude, and is wider for southern locations.We suggest that the effect of temperature could account forthe regional variations in IHD mortality.