2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
body weight loss less than 1.5% were adopted as a permissible level of heat strain according
to the ACGIH criteria (ACGIH, 2006).
RESULTS
Heat stress in the workplaces: Table 1 shows maximal, minimal and average values of
WBGT measured during a working day in the five workplaces investigated. In every
workplace excluding the metal processing factory, the average values of measured WBGT
during work were higher than 28°C (the reference value of the ISO for heat exposure limit for
acclimated workers with moderate metabolic rates). The highest WBGT during work was
measured at the high-rise apartment construction site, the telephone linesmen, the school
building construction, a metal processing factory and a steel foundry, with values of 32.4,
34.0, 31.5, 29.5 and 33.8°C, respectively. The metal processing factory also had several local
hot work spots where the workers were working for short time periods, but frequently in such
extreme heat stress that the values of WBGT exceeded 40-50°C.
Table 1. Maximal, minimal and average values of WBGT (°C) during a working day.
Workplace investigated WBGT-Max WBGT-Min WBGT-Average
High-rise apartment construction site32.426.529.5
Telephone linesmen34.025.630.8
School building construction site31.525.728.6
Metal processing factory29.520.325.1
Steel foundry33.828.030.8
Heat strain of workers: Almost all workers investigated excluding two workers (a school
building construction worker aged 30 years and a steel foundry worker aged 53 years) had
normal oral temperature level below 38°C immediately after work, despite the fact that
environmental heat stress tended to exceed the permissible level of heat exposure during
work. Heart rate during work exceeded the safety limit of ACGIH (180-age) bpm in many
workers involved in construction work and at the steel foundry. Body weight loss during work
was found in almost all workers investigated (the school building construction, the metal
processing factory and the steel plant), many of whom had body weight loss exceeding 1.5 %
and some of whom exceeding 3% (3.6% in a carpenter aged 21 years, 3.3% in a carpenter
aged 64 years, 4.1-4.2% in a steel plant worker aged 54 years). Most of the workers in every
workplace felt uncomfortably hot during work and some of them reported feeling extremely
hot and uncomfortable. Several symptoms relating to heat disorders were experienced by
more than half of the workers at the high-rise apartment construction site and among two of
the telephone linesmen.
DISCUSSION
The ISO7243 (2003) has proposed reference values of heat exposure limits for heatacclimated
and heat-unacclimated persons by physical work intensity (metabolic rates). Since
the present study was carried out from mid-summer to late summer, the workers investigated
are considered to be a predominately heat-acclimated population. Their physical work
intensity (metabolic rates) could be categorized into light and medium levels as the workers
investigated consisted of carpenters, tradesman, guardsman, reinforcing-bar placer,
steeplejack, electrician and furnace workers. Therefore, the reference value of heat exposure
limit for the workers participated in these surveys is estimated 28 30°C in WBGT.
The results of this study, however, clearly showed that the measured WBGT in every hot
workplace exceeded the reference values for heat exposure limits. Furthermore, there were
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