On September 22, for the first time in 16 years, the World Health Organization updated its Global Air Quality Guidelines (AQGs) , based on the rapidly growing scientific evidence that air pollutants can effect human health at even lower concentrations than previously understood. WHO’s new guidelines recommend air quality levels for 6 “classic pollutants”: particulate matter (PM), ozone (O₃), nitrogen dioxide (NO₂) sulfur dioxide (SO₂) and carbon monoxide (CO), and also highlight good practices for the management of certain types of particulates for which there is not yet sufficient evidence to set guideline levels (for example, black carbon/elemental carbon, ultrafine particles, particles originating from sand and dust storms). The press release states: “Clean air should be a fundamental human right and a necessary condition for healthy and productive societies. However, despite some improvements in air quality over the past three decades, millions of people continue to die prematurely, often affecting the most vulnerable and marginalized populations.” The accompanying Fact Sheet provides key statistics, and a report in The Guardian summarizes some of the most shocking , including:
“Every one of the 100 most populous cities in the world exceeded the new WHO guideline for tiny particle pollution in 2020, according to Greenpeace analysis. This includes Tokyo, Shanghai, New York, Lagos, London, and Delhi, with the latter exceeding the limit by 17 times.”
And what is one of the most dangerous kinds of pollution, even in cities? “Mortality risk attributable to wildfire-related PM2·5 pollution: a global time series study in 749 locations” is a pioneering study published on September 1 in Lancet Planetary Health. It analyzes data from 749 cities in 43 countries and regions during 2000–16 and concludes that while wildfires are far from the only source of PM 2.5 pollution in cities, the PM 2.5 exposure from wildfires was more deadly, and longer-lasting, than fine particle pollution from other urban sources – probably because of the chemical makeup and smaller size of the particles in wildfire smoke.