Air pollution is the biggest environmental health risk of our time. It also exacerbates climate change, causes economic losses, and reduces agricultural productivity. It knows no borders – everyone has a responsibility to protect our atmosphere and ensure healthy air for all. By collaborating across borders, sectors, and silos, we can reduce air pollution through collective investments of time, resources and efforts. This International Day of Clean Air for blue skies, we call upon everyone—from governments and corporations to civil society and individuals—to Invest in #CleanAirNow. By tackling air pollution proactively, we can achieve transformative change and secure healthy air for all.