GENEVA (AP) — The World Health Organization (WHO) is setting a higher bar for policymakers and the public in its first update to its air quality guidelines in 15 years.

The U.N. agency says the harmful health effects of air pollution kick in at lower levels than it previously thought.

WHO released its revised guidelines on Wednesday as climate change is a leading topic at the U.N. General Assembly in New York.

Since the last update, better monitoring and science has cleared up the global picture about the effects of six air pollutants on human health.

The agency says 90% of the world’s people already live in areas with at least one particularly harmful type of pollutant.

Every year, the WHO says exposure to air pollution is estimated to cause millions of deaths and the loss of healthy years of life.

“The burden of disease attributable to air pollution is now estimated to be on a par with other major global health risks such as unhealthy diets and tobacco smoking,” said the WHO.

In 2015, the World Health Assembly adopted a landmark resolution on air quality and health, recognizing air pollution as a risk factor for non-communicable diseases such as ischaemic heart disease, stroke, chronic obstructive pulmonary disease, asthma and cancer, and the economic toll they take, according to the WHO.

“The global nature of the challenge calls for an enhanced global response,” said the WHO.