Heat stress evaluation in outdoor Council workers wearing long pants in tropical northern Queensland

Sinclair, Wade H. (2011) Heat stress evaluation in outdoor Council workers wearing long pants in tropical northern Queensland. Report. James Cook University, Townsville, QLD, Australia. (Unpublished)

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Abstract

[Abstract] Collectively, the lack of significant differences in the thermoregulatory demand of completing occupational tasks in either SHORTS or PANTS can potentially be explained via the small area that becomes exposed as a result of wearing SHORTS. When taken into consideration with the additional clothing worn by workers, including footwear and socks, the area available is quite small and lacks the magnitude to elicit changes in TC and subsequently thermal gradients to aide the dissipation of any accumulated heat. Inadequate fluid consumption and poor hydration prior to commencing the workday potentially predispose employees undertaking manual and machinery roles to a greater risk of developing heat-related illnesses. However, it is concluded that, the additional exposed surface area available for heat exchange as a result of wearing knee-length shorts is insufficient to elicit significant differences in the thermoregulatory demands of outdoor Council employees working under the assessed conditions.

[Executive Summary] Previous research of the thermoregulatory demands of wearing long pants or shorts during physical activity has produced differing results. Wearing clothing during physical activity creates a barrier that can impair thermoregulation and impose greater physiological stress on an exercising individual. Increases in oxygen consumption, metabolism, core body temperature (TC) and heart rate (HR) have all been reported while wearing additional layers of clothing. During light to moderate exercise, higher TC and HR have been identified in those wearing coverall‐type clothing compared to shorts although at higher workload intensities, differences between wearing coveralls and shorts diminish. Seventeen males (35.8 ± 10.5 yr) volunteered to participate in each of the two randomised, cross‐over trials conducted 6 days apart: once wearing knee‐length shorts (SHORTS) and once wearing full‐length pants (PANTS). Trials were conducted in the normal occupational environment of participants in tropical northern Queensland during March. Environmental characteristics were not significantly different between trials with predominantly overcast skies and intermittent rain periods. Each trial consisted of participants completing daily occupational tasks as prescribed by crew management and supervisors which consisted of ground maintenance (tasks such as whipper‐snipping, chainsaw operation and clearing shubbery); construction (tasks such as constructing and laying formwork as well as concreting); and plumbing (tasks such as trench‐work and machinist roles). Participants had their body mass and urine assessed each morning prior to commencement and were then equipped with data logging units which recorded throughout the duration of their workday. Body mass assessments were repeated at the conclusion of each workday. There were no significant differences in TC between SHORTS (37.36 ± 0.06°C) and PANTS (37.41 ± 0.05°C; p>0.05) nor for the maximum TC achieved throughout the shift (38.04 ± 0.28 °C for SHORTS and 37.94 ± 0.25 °C for PANTS; p>0.05). This contrasts the results of previous research where shorts were either worn under additional personal protective equipment or compared to coverall‐type clothing that identified lower TC for those wearing shorts under light to moderate workloads. The participants HR responses to the occupational tasks encompassed within the two trials did not differ (86.8 ± 1.9 beats∙min‐1 for SHORTS and 94.1 ± 3.7 beats∙min‐1 for PANTS; p>0.05) with the majority of the workday consisting of very light to moderate (≤ 69% HRMAX) physical activities. Calf skin temperature was found to be significantly lower during the SHORTS trial (32.9 ± 0.4°C vs. 33.8 ± 0.4°C; p<0.01) which is not surprising given its increased convective and evaporative heat loss potential as a result of being exposed. The magnitude of this difference however, was insufficient to result in a reduced mean skin temperature, which was not different between the two trials (32.9 ± 0.3°C for SHORTS vs. 33.4 ± 0.3°C for PANTS; p>0.05). The majority (56.2%) of urine samples provided prior to commencing the workday indicated workers to be in a partially dehydrated state (USG of ≥1.020 g∙mL‐1) and this was not different between trials. Additionally, workers consumed less fluid (1.86 ± 1.30 L for SHORTS and 2.33 ± 1.33 kg for PANTS; p>0.05) than previously suggested (0.6 L∙hr‐1) throughout the workday for similar occupational roles which again did not differ between the trials. The sweat rates reported for the current study (0.30 ± 0.27 L∙hr‐1 for SHORTS and 0.30 ± 0.15 L∙hr‐1 for PANTS; p>0.05) were below those previously reported during physical activity potentially as a result of a reduced thermoregulatory drive to sweat caused by lower skin temperatures. However body mass changes, the magnitude of those identified (2.3 ± 1.9% for SHORTS and 2.5 ± 1.0% for PANTS; p>0.05) have previously been found to induce impaired physiological and cognitive functioning which should be of concern to management given the machinery utilised by the participants. Collectively, the lack of significant differences in the thermoregulatory demand of completing occupational tasks in either SHORTS or PANTS can potentially be explained via the small area that becomes exposed as a result of wearing SHORTS. When taken into consideration with the additional clothing worn by workers, including footwear and socks, the area available is quite small and lacks the magnitude to elicit changes in TC and subsequently thermal gradients to aide the dissipation of any accumulated heat. Inadequate fluid consumption and poor hydration prior to commencing the workday potentially predispose employees undertaking manual and machinery roles to a greater risk of developing heat‐related illnesses. However, it is concluded that, the additional exposed surface area available for heat exchange as a result of wearing knee‐length shorts is insufficient to elicit significant differences in the thermoregulatory demands of outdoor Council employees working under the assessed conditions.

Item ID: 33925
Item Type: Report (Report)
Additional Information:

Report commissioned by: Cairns Regional Council. Submitted May 2011.

Funders: Cairns Regional Council
Date Deposited: 24 Aug 2015 06:26
FoR Codes: 11 MEDICAL AND HEALTH SCIENCES > 1106 Human Movement and Sports Science > 110602 Exercise Physiology @ 50%
11 MEDICAL AND HEALTH SCIENCES > 1117 Public Health and Health Services > 111705 Environmental and Occupational Health and Safety @ 50%
SEO Codes: 92 HEALTH > 9299 Other Health > 929999 Health not elsewhere classified @ 100%
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