A comprehensive evaluation of heat stress and heat strain in a sample of sugarcane cutters in Brazil.

Sugarcane cutters are vulnerable to extreme heat and are at risk for heat-related illness and chronic kidney disease potentially due to high heat strain. We performed a comprehensive assessment of the physiological demands of sugarcane cutters via measurements of metabolic, thermal, and cardiovascular responses. In addition, we assessed cross-shift changes in markers of kidney function. Nine male sugarcane cutters were monitored while working during the spring harvest season in Brazil. Core temperature (Tcore) and heart rate (HR) were continuously recorded, and oxygen consumption was measured during the work shift. Urine and blood samples were collected pre- and post-work shifts. Total sweat loss was calculated using body weight changes and adjusting for water ingestion and urine output. A wet-bulb globe temperature (WBGT) station was used to monitor environmental heat stress. WBGT was ≥ 30°C on seven of the eight study days. Mean and peak Tcore during the work shift were 37.96±0.47°C and 38.60±0.41°C, respectively with all participants surpassing a Tcore of 38°C. Mean and peak HR during the work shift were 137±14 and 164±11 bpm, respectively. Percent of maximal oxygen consumption was, on average, 53±11%. Workers had a total sweat loss of 7.63±2.31 L and ingested 6.04±1.95 L of fluid. Kidney function (estimated glomerular filtration rate) was reduced from pre- to post-work shift (Δ -20±18 mL·min·1.73m2 ). We demonstrated that sugarcane cutters performing prolonged work during a period of high environmental heat stress display high levels of heat strain, high water turnover, and reduced kidney function.