UN Secretary-General Antonio Guterres on Wednesday urged the international community to invest in clean air to save lives and combat climate change.

In his message for the International Day of Clean Air for Blue Skies, observed on Sept. 7, the UN chief said "99 percent of humanity breathes polluted air, leading to an estimated 8 million premature deaths including more than 700,000 children under five."

Pollution is also choking economies and heating up the planet adding "fuel to the fire" of the climate crisis, Guterres warned, stressing that pollution disproportionally affects those most vulnerable in society, including women, children and older persons.

"Yet, pollution is a silent killer that can be stopped," he pointed out.

Guterres highlighted actions both governments and businesses should take: to phase out fossil fuels, strengthen air quality monitoring, enforce air-quality standards, boost renewable energy, transition to clean cooking, build sustainable transport and sustainable waste management systems, clean up supply chains and reduce harmful emissions.

"It is also critical to put a price on carbon," he said.

The UN chief also called on development organizations, financial institutions and philanthropies to redirect financial capital behind clean-air technologies to tackle the triple planetary crisis -- pollution, climate crisis, biodiversity loss. "Above all, we must work together at the regional and global levels," he said.

"Investing in clean air saves lives, combats climate change, strengthens economies, builds fairer societies and advances the Sustainable Development Goals," Guterres noted.