Determination of waste workers’ physical and psychological load using biometric data: A cross-sectional study (Preprint)

BACKGROUND Waste management workers experience high levels of stress and physical strain related to their work environment. Especially during summer, the waste work environment is rarely air-conditioned, and physical illnesses related to high body and environmental temperatures, such as heatstroke, are increasing in the field due to climate change. There is very little empirical evidence to support effective health management practices for waste management workers. OBJECTIVE This cross-sectional study investigated the effect of summer temperatures on the heart rate of waste management workers and determined their work and psychological load. METHODS A biometric measurement system was installed in an industrial waste management facility in Japan to understand the actual working conditions of 29 workers in the facility. A biometric measurement system consisted of sensing wear for data collection and biometric sensors for measuring heart rate measurement, and measured HR and physical activity based on electrocardiogram (ECG) signals. The participants were split into two groups: Group A (n=22, AGE: 35.5±16.8 (years, mean±SD)) was responsible for the transport, dismantling, and sorting of industrial waste, and Group B (n=7, AGE: 33.3±12.7 (years, mean±SD)) for the maintenance and repair of the facility. RESULTS This study investigated the effects of worker characteristics and biometric indices on workers’ physical and psychological loads during waste handling operations. The results showed that compared with workers who did not handle waste, those who did had lower PA and body surface temperature, lower HRV parameters (NN50, pNN50, RMSSD) associated with higher psychological load, and higher LF/HF and LF power associated with stress. There were no significant differences in HR, heart rate interval RRI, and workload %HRR. In addition, multiple regression analysis was used to estimate the factors affecting workload: work activity, body surface temperature, and age (adjusted R2 = 0.449). The LF/HF (low frequency/high frequency) ratio, indicating psychological load, could be inferred from the heart rate interval, body surface temperature, years of experience, and LF power influenced by the autonomic nervous system (adjusted R2 = 0.356). CONCLUSIONS The results showed that workers’ psychological load was not related to their physical workload but was affected by the biological parameters of body surface temperature and heart rate variability. The psychological load of waste workers dealing directly with waste was high, regardless of their physical activity, whereas workers who did not deal with waste directly had a low psychological load, even with high physical activity. These findings underline the need for promoting sustainable work relationships and indicate that a quantitative understanding of harsh working conditions is important for improving work quality and reducing health hazards.