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.     

Taiwanese farm workers’ pesticide knowledge,attitudes, behaviors and clothing practices

The purpose of this study was to assess Taiwanese fruit farm workers’ knowledge, attitudes, behaviours, and clothing practices regarding pesticide activities. Seventy-seven fruit farm workers from four districts of Tainan City, Taiwan completed the questionnaire. Results indicated that farmer workers had a good overall level of knowledge of the adverse effects of pesticides on human health and most had experienced symptoms of pesticide poisoning. Farm workers’ attitudes toward pesticide use and handling indicated that they saw pesticides useful in controlling pests. Farm workers indicated the limited availability of comfortable clothing designed for a hot and humid climate while still providing sufficient protection was the main reason for not wearing personal protective clothing (PPC) and personal protective equipment (PPE). Emphasis on safety precautions is needed when using pesticides, and the importance of PPC and PPE is essential for the health of farm workers.     

Clothing as a dynamic system presenting problems in predicting performance

Prediction of the performance of personnel undertaking physical work in a hot environment is generally achieved by the use of factors for work rate, clothing and climate. A study is reported in which volunteer subjects worked at a fixed rate in five different climates wearing two different clothing assemblies, one semi-permeable, the other impermeable to water vapour. In addition to assessing likely work times in the various climate and clothing combinations, an analysis of the climatic predictors of performance has been undertaken. Whereas in the impermeable suit, predicted work times appeared to be based almost solely on the dry bulb temperature, those in the semi-permeable clothing were well predicted by the WBGT Index. There was no indication that this index would have a greater weighting for the dry bulb component, despite the clothing being partly restrictive to water vapour. If any adjustment is necessary it should be to slightly increase the weighting of the wet bulb.     

Effects of Hoods and Flame-Retardant Fabrics on WBGT Clothing Adjustment Factors

Personal protective clothing (PPC) may include hoods and flame-retardant (FR) fabrics that may affect heat transfer and, thus, the critical wet bulb globe temperature (WBGT crit) to maintain thermal equilibrium. The purpose of this study was to compare the differences in WBGT crit for hooded vs. nonhooded versions of particle barrier and vapor barrier coveralls as well as for coveralls made of two flame-retardant fabrics (INDURA cotton and Nomex). Acclimated men (n = 11) and women (n = 4) walked on a treadmill in a climatic chamber at 180 W/m2 wearing four different ensembles: limited-use, particle barrier coveralls with and without a hood (Tyvek 1427), and limited-use vapor barrier coveralls with and without a hood (Tychem QC, polyethylene-coated Tyvek). Twelve of the participants wore one of two flame-retardant coveralls. All participants wore standard cotton clothing. Progressive exposure testing at 50% relative humidity (rh) was designed so that each subject established a physiological steady-state followed by a clear loss of thermal equilibrium. WBGT crit was the WBGT 5 min prior to a loss of thermal equilibrium. Hooded ensembles had a lower WBGT crit than the nonhooded ensembles. The difference suggested a clothing adjustment of 1 degrees C for hoods. There were no significant differences among the FR ensembles and cotton work cloths, and the proposed clothing adjustment for FR coveralls clothing is 0 degrees C.     

Heat stress standard ISO 7243 and its global application

This paper presents heat stress Standard ISO 7243, which is based upon the wet bulb globe temperature index (WBGT), and considers its suitability for use worldwide. The origins of the WBGT index are considered and how it is used in ISO 7243 and across the world as a simple index for monitoring and assessing hot environments. The standard (and index) has validity, reliability and usability. It is limited in application by consideration of estimating metabolic heat and the effects of clothing. Use of the standard also requires interpretation in terms of how it is used. Management systems, involving risk assessments, that take account of context and culture, are required to ensure successful use of the standard and global applicability. For use outdoors, a WBGT equation that includes solar absorptivity is recommended. A 'clothed WBGT' is proposed to account for the effects of clothing. It is concluded that as a simple assessment method, ISO 7243 has face validity and within limits is applicable worldwide.     

An evaluation of heat stress indices (ISO 7243, ISO/DIS 7933) in the prediction of heat strain in unacclimated men

Summary The ISO 7243 heat stress standard based on the wet bulb globe temperature (WBGT) heat stress index and the analytical standard proposal ISO/DIS 7933 were evaluated in eight physically trained and eight untrained, unacclimated men during prolonged light exercise carried out while wearing industrial work clothing. The exercise tests were done in a thermoneutral (20°C/40%), a warm humid (30°C/80% humidity), and a hot dry (40°C/20% humidity) environment. Both of the standards were effective in predicting the excessive thermal strain observed in the dry and humid heat (WBGT, 28°C). In dry heat, neither of the standards took into account the higher sweating capacities of the physically trained men. The large inter-individual variability in the physiological responses to heat stress questioned the calculations of definite allowable exposure times (ISO/DIS 7933).     

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 of helicopter aircrew wearing immersion suit

The objectives of the present study were to define the lowest ambient air and cabin temperatures at which aircrews wearing immersion protection are starting to experience thermal discomfort and heat stress during flight operations, and to characterize during a flight simulation in laboratory, the severity of the heat stress during exposure to a typical northern summer ambient condition (25 degrees C, 40% RH). Twenty male helicopter aircrews wearing immersion suits (insulation of 2.2 Clo in air) performed 26 flights within an 8-month period at ambient temperatures ranging between -15 and 25 degrees C, and cabin temperatures ranging between 3 and 28 degrees C. It was observed based on thermal comfort ratings that the aircrews were starting to experience thermal discomfort and heat stress at ambient and cabin air conditions above 18 degrees C and at a WBGT index of 16 degrees C. In a subsequent study, seven aircrews dressed with the same clothing were exposed for 140 min to 25 degrees C and 40% RH in a climatic chamber. During the exposure, the aircrews simulated pilot flight maneuvers for 80 min followed with backender/flight engineer activities for 60 min. By the end of the 140 min exposure, the skin temperature, rectal temperature and heart rate had increased significantly to 35.7 +/- 0.2 degrees C, 38.4 +/- 0.2 degrees C and between 110 and 160 beats/min depending on the level of physical activity. The body sweat rate averaged 0.58 kg/h and the relative humidity inside the clothing was at saturation by the end of the exposure. It was concluded that aircrews wearing immersion suits during the summer months in northern climates might experience thermal discomfort and heat stress at ambient or cabin air temperature as low as 18 degrees C.     

Heat exposure in the Canadian workplace

Exposure to excessive heat is a physical hazard that threatens Canadian workers. As patterns of global climate change suggest an increased frequency of heat waves, the potential impact of these extreme climate events on the health and well‐being of the Canadian workforce is a new and growing challenge. Increasingly, industries rely on available technology and information to ensure the safety of their workers. Current Canadian labor codes in all provinces employ the guidelines recommended by the American Conference of Governmental Industrial Hygienists (ACGIH) that are Threshold Limit Values (TLVs) based upon Wet Bulb Globe Temperature (WBGT). The TLVs are set so that core body temperature of the workers supposedly does not exceed 38.0°C. Legislation in most Canadian provinces also requires employers to install engineering and administrative controls to reduce the heat stress risk of their working environment should it exceed the levels permissible under the WBGT system. There are however severe limitations using the WGBT system because it only directly evaluates the environmental parameters and merely incorporates personal factors such as clothing insulation and metabolic heat production through simple correction factors for broadly generalized groups. An improved awareness of the strengths and limitations of TLVs and the WGBT index can minimize preventable measurement errors and improve their utilization in workplaces. Work is on‐going, particularly in the European Union to develop an improved individualized heat stress risk assessment tool. More work is required to improve the predictive capacity of these indices. Am. J. Ind. Med. 53:842–853, 2010. © 2010 Wiley‐Liss, Inc.     

Prediction of rectal temperature by the Questemp II personal heat strain monitor under low and moderate heat stress

This study assessed the use of aural canal temperature measured with the Questemp II personal heat strain monitor (Tq) relative to rectal temperature (Tre) during simulated industrial work in three different wet bulb globe temperatures (WBGT). Sixteen subjects performed walking and arm curl exercise at a rate of 300 kcal/hour for 4 hours while wearing Saranex protective coveralls in 18, 23, and 27 degrees C WBGT environments and wearing the Questemp II. Correlations were determined between Tre and Tq for the three conditions and for all conditions combined. Pearson r values were 0.48 (18 degrees C WBGT), 0.42 (23 degrees C WBGT), 0.38 (27 degrees WBGT), and 0.50 (all trials). Because a major concern is safe maximum core body temperature, means and standard deviations for differences between Tre and Tq were assessed at peak temperatures to determine the predictability of Tre from Tq solely at these points. Large standard deviations in delta values relative to a small overall tolerable temperature range ruled out the use of Tq in this manner. Based on the current data, aural canal temperature as measured with the Questemp II did not provide an accurate reflection of Tre across time nor at peak core temperatures during low to moderate heat strain.     

荧光标记法用于观察医护人员个人防护用品脱摘时的污染

 目的 评价荧光标记法对改善医护人员个人防护用品(PPE)脱摘时污染的效果。方法 在成都市8所三级医院招募69名医护人员进行PPE穿脱培训,并分别在培训前、培训后当日、培训后半个月及培训后一个月采用紫外线-荧光标记法考核PPE脱摘效果,记录脱摘后内层衣物及皮肤表面残留荧光污染点数及部位,比较污染点数及污染率的变化情况。结果 与培训前相比,所有医护人员在培训后当日、培训后半个月及培训后一个月脱摘PPE后残留荧光污染点数均减少(Z值分别为5.306、5.813、6.641,均P<0.001),其中女性、护士、初级与中级职称医护人员在培训后污染率较培训前明显下降(均P<0.05)。随时间推移,3次考核医务人员荧光污染点数逐渐减少(均P<0.05)。工作鞋在PPE脱摘过程中最容易受到污染。结论 医护人员在脱摘PPE过程中容易受到污染,经过实操培训可以降低脱摘PPE后污染率,改善污染情况,荧光标记法可以用于观察PPE脱摘过程中的污染情况。     

Hearing protector use in noise-exposed workers: a retrospective look at 1983

Although hearing protectors have been available for more than 60 years, little field surveillance has been done to assess their appropriate wear in noisy occupational environments. This study examined historical field survey data to determine whether workers use hearing protection when exposed to loud noise. Data from the 1981-83 NIOSH National Occupational Exposure Survey were analyzed to determine whether workers in noise greater than or equal to 85 dBA were using hearing protection. The study also looked at the effect of company personal protective equipment (PPE) policies on hearing protector compliance. This study found that, in 1981-83, an estimated 4.1 million industrial workers were exposed to noise greater than or equal to 85 dBA. Of these, 41% were wearing some form of hearing protection. This percentage varied from 79% of workers exposed in SIC 76 (Miscellaneous Repair Service) to less than 1% in Communications (SIC 48), Wholesale Trade Nondurable Goods (SIC 51), and Automotive Dealers & Service Stations (SIC 55). Whether an establishment had a written policy on wearing PPE seemed to make no difference, because there appeared to be no tie between the percentage of workers wearing of hearing protection and presence of a PPE policy.     

Comparison of estimated core body temperature measured with the BioHarness and rectal temperature under several heat stress conditions

Monitoring and measuring core body temperature is important to prevent or minimize physiological strain and cognitive dysfunction for workers such as first responders (e.g., firefighters) and military personnel. The purpose of this study is to compare estimated core body temperature (Tco-est), determined by heart rate (HR) data from a wearable chest strap physiology monitor, to standard rectal thermometry (Tre) under different conditions.

?Tco-est and Tre measurements were obtained in thermoneutral and heat stress conditions (high temperature and relative humidity) during four different experiments including treadmill exercise, cycling exercise, passive heat stress, and treadmill exercise while wearing personal protective equipment (PPE).

?Overall, the mean Tco-est did not differ significantly from Tre across the four conditions. During exercise at low-moderate work rates under heat stress conditions, Tco-est was consistently higher than Tre at all-time points. Tco-est underestimated temperature compared to Tre at rest in heat stress conditions and at a low work rate under heat stress while wearing PPE. The mean differences between the two measurements ranged from ?0.1 ± 0.4 to 0.3 ± 0.4°C and Tco-est correlated well with HR (r = 0.795 – 0.849) and mean body temperature (r = 0.637 – 0.861).

?These results indicate that, the comparison of Tco-est to Tre may result in over- or underestimation which could possibly lead to heat-related illness during monitoring in certain conditions. Modifications to the current algorithm should be considered to address such issues.     

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.     

The effects of wind and human movement on the heat and vapour transfer properties of clothing.

This paper integrates the research presented in the papers in this special issue of Holmér et al. and Havenith et al. [Holmér, I., Nilsson, H., Havenith, G., Parsons, K. C. (1999) Clothing convective heat exchange: proposal for improved prediction in standards and models. Annals of Occupational Hygiene, in press; Havenith, G., Holmér, I., den Hartog, E. and Parsons, K. C. (1999) Clothing evaporative heat resistance: proposal for improved representation in standards and models. Annals of Occupational Hygiene, in press] to provide a practical suggestion for improving existing clothing models so that they can account for the effects of wind and human movement. The proposed method is presented and described in the form of a BASIC computer program. Analytical methods (for example ISO 7933) for the assessment of the thermal strain caused by human exposure to hot environments require a mathematical quantification of the thermal properties of clothing. These effects are usually considered in terms of 'dry' thermal insulation and vapour resistance. This simple 'model' of clothing can account for the insulation properties of clothing which reduce heat loss (or gain) between the body and the environment and, for example, the resistance to the transfer of evaporated sweat from the skin, which is important for cooling the body in a hot environment. When a clothed person is exposed to wind, however, and when the person is active, there is a potentially significant limitation in the simple model of clothing presented above. Heat and mass transfer can take place between the microclimate (within clothing and next to the skin surface) and the external environment. The method described in this paper 'corrects' static values of clothing properties to provide dynamic values that take account of wind and human movement. It therefore allows a more complete representation of the effects of clothing on the heat strain of workers.     

A comparison of physiological responses to two types of particle barrier, vapor permeable clothing ensembles.

Chemical protective clothing (PC) use while working results in elevated rectal temperatures (Tre) that limit work time. Particle barrier, vapor permeable (PBVP) PCs allow workers to cool themselves by evaporating some sweat. The purpose of this study was to compare the effects on worker productivity of two types of PBVP suits, a Kleenguard (PPPC) (Kimberly Clark), and a Tyvek (PEPC) (DuPont) suit. Fifteen males in a repeated measures design performed four work tests consisting of a walk/arm curl combination at a time-weighted work rate of 1.0 L/min (300 kcal/hr), two in a wet bulb globe temperature (WBGT) of 26 degrees C and two in a WBGT of 18 degrees C, with subjects wearing each suit once in each environment. No significant difference (p > 0.05) was observed between the suits at 18 degrees C WBGT, but a significant difference was found (p < 0.05) between the suits, with the PPPC having a lower Tre in the WBGT = 26 degrees C at the 80th, 100th, and 120th min. A significant difference (p < .05) was also seen in the 26 degrees C WBGT with the PPPC resulting in a lower heart rate (HR) at the 40th, 60th, 80th, 100th, and 120th min and rate of perceived exertion (RPE) at the 75th, 90th, and 120th min. Additionally, a significant difference (p < .05) was seen between PEPC and PPPC for Tre, delta Tre, mean skin temp (mTsk), delta mTsk, and HR, each regressed against time in the 26 degrees C WBGT. Twelve of the 15 subjects also reported feeling cooler in the PPPC versus the PEPC in either WBGT environment.     

Health quality criteria and the analytical procedures for the evaluation of pacifiers]

The health quality criteria for the evaluation of soothers for babies and young children have been developed and the analytical procedures were collected and indicated for the evaluation purposes. They include: sensory analysis global migration migration of metals (Sb, As, Ba, Cd, Pb, Cr, Hg, Se) to 0.07 M HCl analysis of volatile compounds chemical demand for oxygen presence of reaction accelerators presence of antioxidants The requirements concerning mechanical and chemical parameters and also general safety of the product have been developed and the procedures for the conformity checking of these parameters, based on Polish Standard and the draft project of European Standard EN 14000 series concerning soothers for babies and small children have also been presented. These criteria have been accepted by the Ministry of Health and Social Welfare as suitable for issuing of health certificates for placing on the market as well as for the current sanitary surveillance of soothers taken from the market. The criteria will be obligatory until the EN 1400 Standards come into force being introduced into Polish legislation.     

The effects of work environments on thermal strain on workers in commercial kitchens

The purpose of this study was to clarify the effect of working environments of different kinds of commercial kitchens on the thermal strain of kitchen workers. This study design was cross-sectional study, and data collection was performed during busy time in commercial kitchen from August to September 2006. The research subjects were 8 institutions, involving 7 cookers, and 16 men. Measured environmental variables were air temperature, radiant heat index, wet bulb globe thermometer index (WBGT) in front of the cookers, ambient temperature, and estimated ambient WBGT around the workers. The thermal strain on workers was evaluated by fluid loss, body temperatures, heart rate and amount of physical activity (METs). All average estimated ambient WBGTs in front of cookers were less than 27.5℃. The average heart rate was 107 ± 10 bpm, and average METs was 2.0 ± 0.6. The peak values of upper arm skin temperature and auditory canal temperature were less than 37.5℃. The work environments were affected by the kitchen spaces, cooling devices, heating methods, and heat sources. Even in the midsummer, if environmental temperatures were controlled adequately, estimated ambient WBGTs around workers were below the occupational exposure limit. Work environments and thermal strain on workers in commercial kitchen were not severe.     

Heat balance when wearing protective clothing.

This issue of the Annals of Occupational Hygiene is dedicated to the topic of heat stress evaluation. For this evaluation, several evaluation programs and international standards are available. In order to understand the reasoning and underlying theory behind these programs and standards, a basic knowledge of heat exchange processes between workers and their environment is needed. This paper provides an overview of the relevant heat exchange processes, and defines the relevant parameters (air and radiant temperature, humidity, wind speed, metabolic heat production and clothing insulation). Further it presents in more detail the relation between clothing material properties and properties of clothing ensembles made from those materials. The effects of clothing design, clothing fit, and clothing air permeability are discussed, and finally an overview of methods for the determination of clothing heat and vapour resistance is given.