Heat stress and outdoor-labour losses in Bucharest, Romania

Urban heat stress is a growing public-health concern across European cities under climate change. Yet most continental assessments operate at kilometre scales that cannot resolve the intra-urban contrasts that determine who is actually exposed. We use the recently published UrbClim 100 m dataset (Souverijns et al., 2026, Data in Brief, 65, 112497, doi:10.1016/j.dib.2026.112497) for Bucharest, Romania (1.7 million residents) to quantify present (2011–2020) and projected (2021–2040, 2041–2060) heat stress under two climate scenarios: Current Policies (CurPol, +2.9 °C by 2100) and Green Sustainability (GS, +1.7 °C). We analyzed days with wet-bulb globe temperature (WBGT) above 28°C (onset of significant physiological heat stress) and 31°C (extreme stress with health risk even at low activity), annual lost working hours for intense, moderate, and light outdoor work and their economic impact. Under present climate, WBGT exceeds 28°C on 15–24 days yr^-1across most of the city (cool areas < 3 days in northern Bucharest), while WBGT > 31°C is currently rare and patchy (< 3 days yr^-1 in scattered hotspots). By mid-century, days above 28°C rise by 1.8–17.8 per year under CurPol and by 0.8–12.5 under GS. WBGT > 31°C reach up to 6.5 days yr^-1 for CurPol and 4.4 days yr^-1 for GS. In economic terms, an outdoor construction worker in Bucharest loses about 136 hours per year to heat on average (~€800 at current Romanian wages), with a intra-urban gradient from 10–40 hours per worker per year in the cool northern areas to 160–220 hours per worker per year in the centre of Bucharest and former industrial areas. By 2041–2060 the city mean rises to 244 hours under CurPol (~€1,440) and 206 hours under GS (~€1,220). Moderate intensity urban occupations (services, road maintenance, retail and delivery) show smaller but similarly structured increases. These results give Bucharest's public health authorities and administrations a map of where targeted adaptation (urban greening, cooling-centre siting, outdoor-work rescheduling) would reduce heat-related impact and productivity loss.