An astonishing 99 percent of the world’s population breathes polluted air that exceeds internationally approved limits, with negative health impacts kicking in at much lower levels than previously thought, UN medical scientists have warned. Noting that fossil fuels are responsible for most of the harmful emissions that are linked to acute and chronic sickness, the World Health Organisation (WHO) called for tangible steps to curb their use. The UN agency also urged more governments to take note that it has made significant revisions to its air quality indicators, including for particulate matter – known as PM2.5 – that can enter the bloodstream, along with nitrogen dioxide (NO2), another common urban pollutant and precursor of particulate matter and ozone. “It has been recognised that air pollution has an impact at a much lower level than previously thought,” said Dr. Sophie Gumy, Technical Officer at WHO’s Department of Environment, Climate Change and Health. “So, with all the new evidence that has come up over the last 15 years since the last WHO air quality guideline update, most of the values of the guidelines levels have been reduced. So (for) particulate matter it has been reduced by two, and for nitrogen dioxide it has been reduced by four.” According to the WHO, low and middle-income countries still experience greater exposure to unhealthy levels of particulate matter compared to the global average, but nitrogen dioxide patterns “are different, showing less difference between high and low and middle-income countries”. The agency’s data indicates that 4.2 million people die from exposure to outdoor air pollution, in addition to the 3.8 million whose deaths are linked to household smoke produced by dirty stoves and fuels. And based on WHO’s mathematical modelling of available air pollution data from 80 percent of the world’s urban areas, it indicates that almost every one of us faces an increased risk of heart disease, stroke, lung disease, cancer and pneumonia. As depressing and as dangerous as this situation is, the UN health agency insists that momentum has been growing for better air quality everywhere in the last decade. Proof of this is the fact that more than 6,000 cities in 117 countries now monitor air quality, compared to 1,100 cities in 91 countries a decade ago. Achieving cleaner air is also one of the 17 Sustainable Development Goals, and an increasing number of UN agencies have passed resolutions urging Member States to address the health impacts of smog-filled air. Welcoming the increasing number of cities that have begun to measure air quality for the first time, Dr. Maria Neira, Director, WHO Department of Environment, Climate Change and Health, said that it was particularly significant that data is also being gathered on nitrogen dioxide. NO2 “is a proxy indicator for traffic and it’s telling us what is happening at urban level and how this gas that we know that is so damaging and causing so many respiratory diseases – one of them being asthma – is increasing in many cities around the world.”