Politicians across Europe have a moral responsibility to urgently tackle the continent’s dangerously polluted air, according to Maria Neira, the director of the World Health Organization’s department of environment, climate change and health. On Wednesday a Guardian investigation revealed that Europe is facing a severe public health crisis, with almost everyone on the continent living in areas with dangerous levels of air pollution. It found that 98% of people live in areas that exceed WHO guidelines for PM2.5 – tiny particulates that are linked to 400,000 deaths a year. Almost two-thirds of people live with pollution that is twice the WHO standard. Neira said politicians must act swiftly to reduce the scale and severity of pollution. “As a medical doctor, I cannot resist the temptation to remind people that this is about strokes, this is about heart disease, this is about asthma, this is about lung cancer, diabetes, low birth weight, preterm births, cognitive decline,” she said. “We need to remind people that any time you breathe, you are breathing something toxic into your body which is having a devastating impact.” She said it would not be acceptable for 98% of Europeans to be supplied with dangerously polluted water, and the same should be true for the air they breathe. “People say our guidelines are very strict and very ambitious. But I don’t see ambition in proposing something that will make so many people less sick … Having the knowledge we have [on the health impacts of air pollution] I think there is a clear and absolute moral responsibility.” Last week the European parliament voted to adopt the WHO guidelines on PM2.5, but not until 2035. Neira welcomed the vote, but added: “We strongly urge countries to act swiftly, recognising that any shift in air quality levels will have a direct impact on public health, climate and the environment. Delaying these crucial measures will have severe and immediate consequences for people’s wellbeing and the planet.” The Guardian investigation found that the worst-hit country in Europe is North Macedonia, where almost two-thirds of people live in areas with more than four times the WHO guideline levels of PM2.5. Eastern Europe is significantly worse than western Europe, apart from Italy, where more than a third of people living in the Po valley and surrounding areas breathe air that is four times more polluted than the WHO guideline levels. Javi López, a Spanish MEP with the centre-left group that led a recent push in the European parliament to adopt the WHO guidelines, said the Guardian investigation was “proof that pollution is a visible pandemic in Europe”. He said: “A discussion about not only health, but a discussion about inequalities across Europe – between member states, but also social discussion between areas and classes – should be a top priority for administrations.” In the UK, three-quarters of the population live in areas where exposure to PM2.5 is between one and two times the WHO guidance. On Wednesday the UK prime minister, Rishi Sunak, announced he was watering down a swathe of environmental protections, including a plan to ban petrol and diesel cars from 2030. The London mayor, Sadiq Khan, who has overseen the expansion of an ultra-low emission zone to cover the entire capital in an effort to improve air quality, said it was exactly the wrong time to row back on climate policies. “We are in a climate emergency, and this important investigation starkly highlights the scale and severity of air pollution across Europe,” he said. “Toxic air is linked to hundreds of thousands of premature deaths a year, which is why I am rolling out some of the most ambitious policies of any city in the world to clean up London’s air and tackle climate change.” He said the deadly impacts of pollution and climate change were becoming more and more apparent. “That is why we must act urgently, and why the government’s moves to row back on environment measures flies in the face of common sense and shows they are climate delayers,” Khan said.