The lockdown measures imposed in March 2020 to contain the COVID-19 pandemic led to unprecedented declines in air pollution, noise and physical activity levels in cities. The consequences of these changes for people’s health differed depending on the stringency of the confinement measures and local context, giving insights into how emergency measures can more broadly affect population health. What lessons can be learned for future urban planning policies and emergency preparedness? A study published in Environmental Pollution led by the Barcelona Institute for Global Health (ISGlobal), a center supported by the “la Caixa” Foundation, has attempted to answer these questions.