Hydration status of South African forestry workers harvesting trees in autumn and winter.

OBJECTIVES To determine both the prevalence and severity of dehydration of forestry workers harvesting trees in autumn and winter. METHODS Two cross-sectional observational studies were conducted on convenience samples of 103 and 79 workers in autumn and winter, respectively. The prevalence of dehydration pre- and post-shift was determined using urine specific gravity (U(SG)), and the severity of dehydration by the percent loss of body weight across the shift. RESULTS Pre-shift, 43% in autumn and 47% in winter were dehydrated (U(SG) > 1.020 g ml(-1)) on arrival at work. There was a significant increase (P ≤ 0.001) in the prevalence of dehydration post-shift as 64% (P ≤ 0.001) in autumn and 63% (P = 0.043) in winter were dehydrated. In each area, ±22% had dehydrated by ≥2% loss of body weight. Pre-shift, 23% in autumn and 13% in winter were overhydrated (U(SG) < 1.013 g ml⁻¹). Post-shift, 4% in autumn and 2% in winter were overhydrated. An excessive consumption of hypotonic fluid (water) in combination with a reduced salt intake to prevent hypertension exposed an important minority to the risk of potentially fatal dilutional hyponatremia. Neither dehydration nor hyperhydration was related to season, gender, or job category. CONCLUSIONS During average shifts, the South African forestry workers, regardless of season, gender, or job category, experienced dehydration of a magnitude that compromised both their safety and productivity.