Occupational heat exposure, physical workload, and hydration status among floating net cage workers in Lake Toba

Background Floating net cage (Keramba Jaring Apung [KJA]) aquaculture workers in Lake Toba perform strenuous physical labor in open-water environments. This study investigated the primary determinants of post-shift hydration status among these workers. Methods We conducted a cross-sectional study among 124 active workers across 12 KJA enterprises in Paropo I Village. We evaluated daily fluid intake, physical workload, workplace microclimate, and Body Mass Index. Bivariate analysis yielded crude odds ratios (OR). Candidate variables ( p < 0.25) entered a multivariable logistic regression model. Results Overall, 62.90% of workers experienced post-shift dehydration. Heavy physical workload significantly elevated dehydration risk (Adjusted OR = 5.69; 95% CI: 1.20–26.97; p = 0.03). Adequate fluid intake (≥ 2.50 L/day) strongly reduced risk (Adjusted OR = 0.01; 95% CI: 0.00–0.13; p < 0.01). Conclusion Heavy physical exertion and daily fluid deficits drive occupational dehydration in open-water aquaculture. To mitigate heat strain, implement platform-based drinking stations, scheduled hydration breaks, and visual self-monitoring tools.