An Evaluation of the Physiological Strain Experienced by North American Electrical Utility Workers

Abstract

Electrical power workers must often perform physically demanding tasks in hot and humid environments while wearing heavy insulated clothing. However, little is known about the physiological strain experienced by these workers. PURPOSE: To assess the physiological strain experienced by electrical utility workers during their daily work shifts performed in the heat (29.0-34.4°C). METHODS: Five typical electrical utilities jobs were evaluated in a total of 32 electrical utilities workers (age: 36 ± 9 years; body weight: 97 ± 17 kg): (i) General Labour (n=6), (ii) Bucket Work (n=9), (iii) Networking (n=5), (iv) Combined Work (n=9), and (v) Pole Climbing (n=3). Hydration status was assessed prior to work using urine specific gravity (USG). Core temperature (assessed using a telemetric pill) and heart rate (HR) responses were measured continuously. RESULTS: Before the start of the work period, five participants were considered well hydrated (USG≤1.010; prevalence: 15.6%), six of the participants were classified as seriously dehydrated (USG>1.030; prevalence: 18.8%), with the remaining participants considered as either minimally (n=9; USG: 1.021-1.030; prevalence: 28.1%) or significantly dehydrated (n=13; USG: 1.021-1.030; prevalence: 40.6%). Mean resting core temperature was 37.2 ± 0.3°C. During the work shift average core temperature responses ranged from 37.7 ± 0.1°C in Networking to 38.0 ± 0.4°C in Combined Work while the peak core temperature achieved by a single participant exceeded 38.3°C in all work categories (General Labour, 38.6°C; Bucket Work, 38.7°C; Network 38.4°C; Combined Work, 39.7°C; Pole Climbing, 38.7°C). Furthermore, two participants performing Combined Work experienced severe levels of heat stress reaching peak core temperatures of ∼39.6°C. These individuals spent ∼50% of the 4.5 hour work period at core temperatures exceeding 38.5°C. Mean HR ranged from 31 ± 8 to 57 ± 16 percent of participants’ age predicted HR rate reserve (HRR). Peak HR rate responses achieved levels ≥93% HRR for all jobs with the exception of networking (General Labour: 98%; Bucket Work: 94%; Combined Work: 93%; Pole Climbing: 104%). CONCLUSIONS: We show that electrical utility workers performing common jobs in the heat start their shift in a dehydrated state and experience elevated levels of thermal and cardiovascular strain, resulting in an increased risk for heat-related injuries. SUPPORT: Electrical Power Research Institute.