By JAMEY KEATEN and DREW COSTLEY
GENEVA (AP) — The World Health Organization 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.