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Pilot Study of Heat-stress Exposure Sensing and Heat-warning System for Workers in Outdoor High-temperature Workplace

  • Publication Date:2019-07-17


To establish heat-stress exposure sensing and heat-warning systems for workers in outdoor high-temperature workplace is in urgent needs due to the global warming trend and current record-high temperature situations in Taiwan in recent years. Integrating multidisciplinary expertise of heat-stress exposure assessment, environmental sensing, heterogeneous data fusion, and big data analytics, our research team works together to overcome current data and tool limitations for the purpose of establishing a fast-response heat-stress exposure sensing and heat-warning system for workers in outdoor high-temperature workplace. Eight major tasks are successfully completed.

Prototype of a wearable sensing device is developed after laboratory and field testing. The problems of wearable feasibility, water-proof ability, battery durability, and data transmission of this device have been tackled. Fifty workers in five construction sites were recrucited to wear this prototype. A movable weather station was set up to measure ambient meteorological parameters. Field campaigns were conducted covering three typical summer weather conditions. The collected data were aggregated in the established Labor-WBGT website which has a database with an interface for visualization of measurements.

Construction workers with different job titles and tasks were recruited with totally 58 person-day measurements. They usually work 6 days a week. More than half of the subjects in three sites feel hot during working hours. Higher than 30% of the subjects in all five sites encounter high-temperature instruments or objects every working day; the most frequently encountered high-temperature object is steel. In all five sites, more than 50-60% of the subjects have to work outdoor for more than 3 hours during 10am-3pm. These facts point out the prevalence of construction workers exposed directly under the sun.

Six different types of data were collected, including 5,858 ambient meteorological data measurements, 17,192 wearable device data, roughly 2,000 data from two types of qestionnaires, approsimately 850,000 motion-sensing data from the cellphones, and 103 biological measurements. Wet bulb global temperatures (WBGT) were calculated based on these measurements. The average WBGT in five sites varied from 33.0-37.1℃, depending on the weather conditions and characteristics of the construction sites. Workers' WBGT were also varied among different subjects, due to different job tasks and working micro-environments. Among those workers with more than 90 minutes of measurements, the average WBGT were 24.5-40.0℃. More than 65% of the time in the five sites, all subjects experienced WBGT higher than 32.2℃, i.e. a dangerous zone marked by black flags. Particularly in one construction site, on average 96.9% of the working hours of all ten subjects is black-flag period. Besides carrying the wearable device, another alternative to estimate workers' WBGT is to apply data from the on-stie weather station, which could explain 68% of the variability. These data and analysis emphasize the importance of applying wearable devices and on-site weather sensors for heat-stress monitoring of workers, as well as the urgency of setting appropriate WBGT levels and real-time heat-warning system to protect health of outdoor workers in Taiwan.


KeyWords: outdoor worker, heat-stress, WBGT, exposure assessment, heat warning system, wearable sensing device

  • Source:Division of Occupatinal Hygiene
  • Last updated:108-07-17
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