A laboratory study of the effects of moderate thermal stress on the performance of factory workers

Too hot to carry on? Disinclination to persist at a task in a warm office environment

We investigated the effect of an elevated ambient temperature on performance in a persistence task. The task involved the coding of incorrect symbols and participants were free to decide how long to spend performing this task. Applying a between-subject design, we tested 125 students in an office-like environment in one of the three temperature conditions. The comfort condition (Predicted Mean Vote [PMV] = 0.01) featured an average air temperature of 24 °C. The elevated ambient temperature condition was 28 °C (PMV = 1.17). Condition three employed an airstream of approximately 0.8 m/s, intended to compensate for performance decrements at the elevated air temperature (28 °C, PMV = 0.13), according to Fanger's thermal comfort equation. Participants in the warm condition were significantly less persistent compared with participants in the control and compensation conditions. As predicted by the thermal comfort equation, the airstream seemed to compensate for the higher temperature. Participants' persistence in the compensation and comfort conditions did not differ. Practitioner Summary: A laboratory experiment involving a simulated office environment and three ambient temperature conditions (24 °C, 28 °C and 28 °C plus airstream) showed that persistence at a task is significantly impaired at 28 °C. An airstream of 0.8 m/s at 28 °C compensated for the disinclination to persist with the task.

Subjective symptoms of female workers sorting goods in summer

Subjective musculoskeletal symptoms are more frequently complained about in cold store work and in related conditions than those experienced in normal temperature work. This cross sectional study was undertaken to evaluate the effects of indoor cooling and cold storage goods on the prevalence of subjective symptoms in summer. Female workers sorting cold storage goods (exposed group) were the main subjects of this study (n=47). We also included a group of female workers engaged sorting dry goods as the unexposed to cold group (n=86). Work load for the two groups were estimated according to the recommended criteria. A self-administered questionnaire covering age, occupational career, smoking, alcohol drinking and physical exercise, present or past history of diseases, individual protective measures against cold or heat, and subjective symptoms (60 items) was used. The air temperature of the site at the start of working time for the workers sorting cold storage goods was 22.2℃ which was significantly lower than those measured for the other two work places (25.4℃ and 25.4℃) of the unexposed to cold group. Environmental temperatures at the foot level at the sorting workshop of cold storage goods and dry goods were ca.16℃ and 26℃ all day, respectively. The surface temperatures of cold storage goods were between -2.8℃ and 9.4℃. The surface temperature of dry goods was 26.5℃. Among the working characteristic items, only daily working hours in the exposed group (5.6 ± 0.6 h) were significantly longer than those in the unexposed to cold group (4.6 ± 0.9 h) (p<0.01). The prevalence rates of finger cold sensation, stiffness in the fingers, pain in the wrist, pain in the elbow, back dullness, back pain, low-back cold sensation, foot cold sensation and pain in the foot in the exposed group were significantly higher than those in the unexposed to cold group (p<0.05 or p<0.01). Pain in the fingers, numbness in the fingers, pain in the foot and foot numbness due to the cold in the exposed group were significantly higher than those in the unexposed to cold group (p<0.05 or p<0.01). These results suggest that indoor cooling and/or job activities related to cold storage goods could, to some extent, affect peripheral circulatory disturbances; and it could be regarded as a factor related to musculoskeletal symptoms among the exposed workers.

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 degrees 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.

Comparison of subjective symptoms and cold prevention measures in winter between traffic control workers and construction workers in Japan

To help making comfortable workplaces and to prevent health disorders induced by the exposure to moderate cold in two different groups of out-door workers, we conducted a survey to compare subjective symptoms and cold prevention measures in winter between traffic control workers and construction workers. The subjects of this study were 98 male traffic control workers and 149 male workers engaged in building construction. Work loads of traffic control workers and construction workers were estimated at RMR1-2 and RMR2-4, respectively. All subjects were asked to complete a self-administered questionnaire covering age, occupational career, working figure, present illness, past history of diseases, individual preventive measures to the cold, subjective symptoms in the winter (43 items) and subjective symptoms occurred during daytime working in the winter (6 items). In two parts of the construction workplaces (the place where a morning assembly was held and on the 7th floor of the construction site) dry bulb, wet bulb and globe temperatures were measured in January. Windchill Index (kcal/cm,(2) x h) was calculated by the measured dry bulb temperature and wind velocity. Mean values of dry bulb temperature between 9:00 and 16:30 in the place where a morning assembly was held for three days were between 4.8 +/- 1.2 degrees C at 9:00 am and 9.3 +/- 1.1 degrees C at noon. Mean values of Windchill Index in the place where a morning assembly was held were between 490.8+/-23.9 kcal/cm(2) x h at 9:30 am and 608.2+/-47.3 kcal/cm(2) x h at 2:30 pm. Occupational career, monthly working days, daily working hours, one way commuting hours, and daily smoking numbers of the traffic control workers were significantly shorter than the construction workers (p<0.01). There were no significant differences in the prevalence of chillness in the arms and legs between the traffic control workers (5.1%) and the construction workers (0.7%). Prevalence of wearing a warm underwear, body warmer, warm trousers, underpants, warm socks, shoe warmer and muffler in the traffic control workers were significantly higher than the construction workers. The subjective symptoms in winter complained most frequently were shoulder stiffness (51.0%), finger cold sensation (50.0%) and neck stiffness (48.0%) in the traffic control workers, and were easy to get fatigued (49.0%), lumbago (48.3%) and finger cold sensation (47.7%) in the construction workers. On the basis of the results obtained, it is clearly shown that the two groups are at the risk of disorders due to their working environment. Therefore, these workers are needed to undergo occupational health programs for prevention of cold exposure disorders. Applications of preventive countermeasures for both groups are discussed.

Accounting for human variability and sensitivity in setting standards for electromagnetic fields

Biological sensitivity and variability are key issues for risk assessment and standard setting. Variability encompasses general inter-individual variations in population responses, while sensitivity relates to unusual or extreme responses based on genetic, congenital, medical, or environmental conditions. For risk assessment and standard setting, these factors affect estimates of thresholds for effects and dose-response relationships and inform efforts to protect the more sensitive members of the population, not just the typical or average person. While issues of variability and sensitivity can be addressed by experimental and clinical studies of electromagnetic fields, investigators have paid little attention to these important issues. This paper provides examples that illustrate how default assumptions regarding variability can be incorporated into estimates of 60-Hz magnetic field exposures with no risk of cardiac stimulation and how population thresholds and variability of peripheral nerve stimulation responses at 60-Hz can be estimated from studies of pulsed gradient magnetic fields in magnetic resonance imaging studies. In the setting of standards for radiofrequency exposures, the International Commission for Non-Ionizing Radiation Protection uses inter-individual differences in thermal sensitivity as one of the considerations in the development of "safety factors." However, neither the range of sensitivity nor the sufficiency or excess of the 10-fold and the additional 5-fold safety factors have been assessed quantitatively. Data on the range of responses between median and sensitive individuals regarding heat stress and cognitive function should be evaluated to inform a reassessment of these safety factors and to identify data gaps.

Subjective Symptoms among Female Workers and Winter Working Conditions in a Consumer Cooperative

Subjective musculoskeletal symptoms are more frequently complained about in cold store work and in related conditions than in normal temperature work. This cross sectional study was undertaken (a) to explore the prevalence of subjective symptoms in winter among a group of female workers engaged in classification of cold storage goods, and in a group of female checkers in several supermarkets of a large consumer cooperative; and (b) to give recommendations for improving the winter working conditions of these workers. The subjects consisted of 46 workers engaged in classification of cold storage goods, 56 checkers operating a laser scanner in supermarkets and 59 office workers (control group). Work loads for the three groups were estimated according to the recommended criteria. A self-administered questionnaire covering age, occupational career, smoking, alcohol drinking and physical exercise, present or past history of diseases, individual protective measures against cold, and subjective symptoms (54 items) was used. The air temperature of the working site at the opening time for classification workers was 4.8 degrees C which was significantly lower than those measured for the other two work places (12.1 degrees C and 15.8 degrees C). About 70 to 80% of classification workers complained of cold sensation in different body regions, as well as shoulder stiffness, and problems related to the back. The supermarket checkers and office workers had a high prevalence of cold sensation in their feet. The frequencies of using warm clothes and foot heaters, as an individual measure to work comfortably in winter among the classification workers and the checkers were significantly higher than that among the office workers. We concluded that work difficulty due to moderate cold exposure among workers in the consumer cooperative could be reduced by some physical activity as well as proper clothes.

Evaluating the efficacy of a thermal exposure chamber designed for assessing workers' thermal hazard

This study was conducted on a thermal exposure chamber designed for assessing workers' thermal hazard. In order to assess the efficacy of the studied chamber, three environmental conditions were selected to simulate high, middle and low thermal impact situations, with air temperatures (Ta) of 43.12, 36.23 and 25.77 masculine C, globe temperatures (Tg) of 44.41, 41.07 and 29.24 masculine C, relative humidity (RH) of 77, 59 and 39%, and air flow velocities (Va) of 1.70, 0.91 and 0.25 m/s, respectively. For the three specified thermal impact conditions, results show that the coefficients of variation (CVs) for Ta, Tg, RH and Va measured in the chamber studied were consistently less than 10%, except for Va under the low thermal impact condition (=50%). For each specified thermal impact condition, we generated 1,000 environmental combinations by using the Monte Carlo simulation approach according to the variations obtained from the four environmental factors. We directly adopted the ISO 7933 approach to estimate the allowable exposure time (AET) for each simulated environmental condition. This study yielded a range in the 95% confidence interval (95% CI) of the estimated AETs for the three specified thermal impact conditions which were consistently less than 5 min. We further conducted the sensitivity analysis to examine the effect of the four environmental factors on estimating AETs. We found Va was the least important factor in estimating AETs for any specified thermal impact condition. In conclusion, although Va was found with great variation for the chamber specified in the low thermal impact condition, the exposure chamber studied can still be regarded as a feasible one for assessing workers' thermal hazard.