It said urgent action was needed to reduce exposure to air pollution, ranking its burden of disease on a par with smoking and unhealthy eating, AFP reported.
“WHO has adjusted almost all the air quality guideline levels downwards, warning that exceeding the new... levels is associated with significant risks to health,” it said.
“Adhering to them could save millions of lives.”
The guidelines aim to protect people from the adverse effects of air pollution and are used by governments as a reference for legally-binding standards.
The UN health agency last issued air quality guidelines, or AQGs, in 2005, which had a significant impact on pollution abatement policies worldwide.
However, the WHO said in the 16 years since, a much stronger body of evidence had emerged, showing how air pollution impacts on health at lower concentrations than previously understood.
“The accumulated evidence is sufficient to justify actions to reduce population exposure to key air pollutants, not only in particular countries or regions but on a global scale,” the organisation said.
The new guidelines come just in time for the COP26 global climate summit held in Glasgow from October 31 to November 12.
The WHO said that alongside climate change, air pollution was one of the biggest environmental threats to human health. Improving air quality would enhance climate change mitigation efforts, and vice versa, it said.