The physiological strain incurred during electrical utilities work over consecutive work shifts in hot environments: A case report

ABSTRACT

Purpose: In this article, we evaluated physiological strain in electrical utilities workers during consecutive work shifts in hot outdoor conditions.

Methods: Four highly experienced electrical utilities workers were monitored during regularly scheduled work performed in hot conditions (∼34°C) on two consecutive days. Worker hydration (urine specific gravity) was assessed prior to and following work. The level of physical exertion was determined by video analysis. Body core temperature (T_core) and heart rate (HR; presented as a percentage of maximum, %HR_max) were monitored continuously. Responses were reported for each worker individually and as a group mean ± standard deviation.

Results: According to current guidelines, all workers were dehydrated prior to work on both days (urine specific gravity: day 1, 1.025 ± 0.005; day 2, 1.029 ± 0.004) and remained dehydrated following work (urine specific gravity: day 1, 1.027 ± 0.015; day 2, 1.032 ± 0.004) except for one worker on day 1 (urine specific gravity of 1.005). On day 1, the proportion of the work shift spent at rest (as defined by the American Conference for Governmental and Industrial Hygienists, ACGIH) was 51 ± 15% (range: 30–64%). Time spent resting increased in all workers on the second day reaching 66 ± 5% (range: 60–71%) of the work shift. Work shift average T_core was 37.6 ± 0.1°C (range: 37.5–37.7°C) and 37.7 ± 0.2°C (range: 37.5–37.9°C) on days 1 and 2, respectively. Peak T_core surpassed the ACGIH recommended threshold limit of 38.0°C for work in the heat in three workers on day 1 (38.1 ± 0.2°C, range: 37.8–38.2°C) while all workers exceeded this threshold on day 2 (38.4 ± 0.2°C, range: 38.2–38.7°C). By contrast, work shift average (day 1, 67 ± 7%HR_max, range: 59–74%HR_max; day 2, 65 ± 4%HR_max, range: 60–70%HR_max) and peak (day 1, 90 ± 6%HR_max, range: 83–98%HR_max; day 2, 87 ± 10%HR_max, range: 73–97%HR_max) HR were similar between days.

Conclusion: This case report demonstrates elevations in thermal strain over consecutive work shifts despite decreases in work effort in electrical utilities workers during regular work in the heat.

Keywords:

• Climate change
• heat exposure
• heat waves
• occupational heat stress
• workers

Acknowledgments

We greatly appreciate all of the volunteers for taking their time to participate in this study.

Funding

This research was supported by the Ontario Ministry of Labour and the Electric Power Research Institute.