Author(s): LIM, G., TAN, P., KWEK, J.H., TRAN, T., LEOW, C.H.W., LEE, J.K.W., LEE, J.Y., Institution: HEAT RESILIENCE AND PERFORMANCE CENTRE, NATIONAL UNIVERSITY OF SINGAPORE, Country: SINGAPORE, Abstract-ID: 2113

INTRODUCTION:
Despite the increasing number of parcel delivery workers’ fatalities and injuries, there have been few comprehensive investigations into the workers’ occupational health risks. This study aimed to quantify delivery workers’ workload, assess their physiological strain, and investigate the impact of workload on their physiological strain.
METHODS:
A total of forty male delivery workers from two logistics work sites in South Korea (site A and site B) participated in this study. Wet Bulb Globe Temperatures (WBGT) at each site were measured throughout the work shifts. Workload, work environment, and workers’ dietary behaviors were investigated through in-depth interviews and wearable devices. Workload was quantified using working hours per day, workdays per week, the number of parcels, and total step count on the measurement day. Workers’ body core temperature (Tc), heart rate (HR) and step count were continuously recorded throughout their shifts, while body mass was measured at four timepoints: pre-shift, mid-shift, post-shift, and the next morning. Urine specific gravity (USG) was measured pre-shift and the next morning.
RESULTS:
Mean WBGT was below 20°C throughout the work shifts. The workers worked 11.7 hours per day on average and 5–7 days per week. The number of parcels they delivered on the measurement day ranged from 150 to 571 and step counts ranged from 14,400 to 38,068. Regarding nutrition, 45% of the workers skip both breakfast and lunch on busy days, with 25% skipping both meals every working day. 32.5% of the workers’ maximum Tc exceeded 38°C, which is the upper limit of the Threshold Limit Values® for heat stress from the American Conference of Governmental Industrial Hygienists guidelines. 47.5% of the workers exceeded 80% of their age predicted maximum HR during their shift. 87.5% of the workers showed a decrease in their body mass after their shifts and 25% lost more than 2 kg. Categorizing dehydrated workers as those with 1.025 or greater values of USG, 15% and 17.5% were dehydrated in the pre-shift and next morning timepoints, respectively. The number of parcels delivered by the workers showed significant correlations with both peak HR (Pearson’s R = 0.499, p = 0.035) and their body mass loss (Pearson’s R = 0.665, p = 0.001) for site A. Total step count also displayed a significant correlation with the maximum value of workers’ Tc for site A (Pearson’s R = 0.484, p = 0.036). No significant correlation between workload and physiological responses was found for site B in this study.
CONCLUSION:
The results of this study demonstrated that workers’ workload may be related to their physiological strain. This study suggests that heat-preventive measures, such as appropriate work-rest cycles, may be beneficial to the physical health of parcel delivery workers. Future research might further investigate workers’ nutrition and hydration, the effect of extreme temperature conditions on physiological strain, as well as the impact of workload on workers’ performance.