BACKGROUND: We sought to evaluate potential mediators of the relationship between heat exposure and traumatic injuries in outdoor agricultural workers.
METHODS: Linear mixed models were used to estimate associations between maximum work-shift Wet Bulb Globe Temperature (WBGTmax) and post-shift vigilance (reaction time) and postural sway (total path length) in a cross-sectional sample of 46 Washington State tree fruit harvesters in August-September 2015.
RESULTS: The mean (SD) WBGTmax was 27.4 (3.2)°C in August and 21.2 (2.0)°C in September. The mean pre-work-shift participant urine specific gravity indicated minimal dehydration. Twenty-four percent of participants exhibited possible excessive sleepiness. There was no association between WBGTmax and post-shift reaction time or total path length.
CONCLUSIONS: Heat exposure was not associated with impaired vigilance or balance in this study, in which the overall mean (SD) WBGTmax was 25.9 (4.2)°C. However, the study identified opportunities to ensure adequate pre-work-shift hydration and to optimize sleep and work-shift timing in order to reduce occupational injury and heat-related illness risk.