An Umbrella Review of Systematic Reviews and Meta-Analyses on Occupational Heat Exposure, Health Risks, and Productivity Losses Globally

Abstract

Background: Workplace heat exposure, intensified by climate change, increasingly threatens workers’ health, safety, and productivity, especially in the agriculture, construction, and manufacturing sectors. However, current evidence is fragmented due to varied study designs, and the absence of an integrated, multidisciplinary synthesis. Objectives: This umbrella review synthesizes findings from current systematic reviews and meta-analyses to appraise the health and productivity outcomes of workplace heat exposure, assess evidence quality, and identify critical research and policy gaps. Methods: Fourteen systematic reviews and meta-analyses (published up to 31st March 2025) were included following predefined (PECOS) criteria. Methodological fidelity was analyzed using the AMSTAR checklist, and the strength of evidence was evaluated using the GRADE approach. Results: The fidelity of the included reviews was rated from moderate to high, while the robustness of evidence spanned from low to moderate due to study heterogeneity and observational designs. Consistent evidence links workplace heat exposure to higher risks of heat-related illness, reduced eGFR (AOR = 3.50, 95% CI: 1.30–9.40) resulting renal impairment, cognitive decline, and injuries (1% increase in risk per 1℃ rises in temperature). Emerging findings suggests heat-induced sub-cellular and molecular damage (i.e., increased 8-OHdG, HSP70), reduced sperm quality, indicating cellular dysfunction. Women and relocated workers face greater physiological strain. Productivity losses affect 30–60% of exposed workers, with prior estimates suggesting annual global economic losses of approximately $2.1 trillion. Conclusions: Workplace heat hazards significantly threaten global workforce health and economic resilience. Urgent, coordinated interventions, robust policy measures, and high-quality longitudinal research are required to alleviate these risks.