Time-motion analysis as a novel approach for evaluating the impact of environmental heat exposure on labor loss in agriculture workers

ABSTRACT

Introduction: In this study we (i) introduced time-motion analysis for assessing the impact of workplace heat on the work shift time spent doing labor (WTL) of grape-picking workers, (ii) examined whether seasonal environmental differences can influence their WTL, and (iii) investigated whether their WTL can be assessed by monitoring productivity or the vineyard manager's estimate of WTL. Methods: Seven grape-picking workers were assessed during the summer and/or autumn via video throughout four work shifts. Results: Air temperature (26.8 ± 4.8°C), wet bulb globe temperature (WBGT; 25.2 ± 4.1°C), universal thermal climate index (UTCI; 35.2 ± 6.7°C), and solar radiation (719.1 ± 187.5 W/m²) were associated with changes in mean skin temperature (1.7 ± 1.8°C) (p < 0.05). Time-motion analysis showed that 12.4% (summer 15.3% vs. autumn 10.0%; p < 0.001) of total work shift time was spent on irregular breaks (WTB). There was a 0.8%, 0.8%, 0.6%, and 2.1% increase in hourly WTB for every degree Celsius increase in temperature, WBGT, UTCI, and mean skin temperature, respectively (p < 0.01). Seasonal changes in UTCI explained 64.0% of the seasonal changes in WTL (p = 0.017). Productivity explained 36.6% of the variance in WTL (p < 0.001), while the vineyard manager's WTL estimate was too optimistic (p < 0.001) and explained only 2.8% of the variance in the true WTL (p = 0.456). Conclusion: Time-motion analysis accurately assesses WTL, evaluating every second spent by each worker during every work shift. The studied grape-picking workers experienced increased workplace heat, leading to significant labor loss. Monitoring productivity or the vineyard manager's estimate of each worker's WTL did not completely reflect the true WTL in these grape-picking workers.

KEYWORDS:

• Europe
• heat strain
• heat stress
• irregular work break
• productivity
• WBGT
• UTCI

Abbreviations

ΔTsk	=	difference between the baseline mean skin temperature (i.e., at time 0) and the current mean skin temperature (°C)
solR	=	solar radiation (W/m2)
Tair	=	air temperature (°C)
Tsk	=	mean skin temperature (°C)
UTCI	=	universal thermal climate index (°C)
WBGT	=	wet bulb globe temperature (°C)
WTL	=	work time spent on labor (time, min:sec)
WTB	=	work time spent on irregular work breaks (time, min:sec)
WTBshade	=	work time spent on irregular breaks in the shade (time, min:sec)
WTBsun	=	work time spent on irregular work breaks under the sun (time, min:sec)

Disclosure of potential conflicts of interest

There are no relevant financial or other relationships that might be perceived as leading to a conflict of interest in relation to this work. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Acknowledgments

The authors are grateful to the volunteers and the vineyard management for their participation in this study.

Funding

The study has received funding from the European Union's Horizon 2020 research and innovation programme under the Grant agreement no. 668786.