In Santiago, this winter was different. The mountains surrounding the city \u2013 the same ones that usually trap smog and turn it into a \u201cpressure cooker\u201d \u2013 were visible more days than usual.<\/p>\n
For nearly 30 years Chile\u2019s capital has been experimenting in how to reduce air pollution; in the last few years the work has at last begun paying dividends and 2025 was the third best year in terms of fewest hours of critical pollution episodes<\/a> since the first atmospheric prevention and decontamination plan in 1997. Over the last decade, hours of exposure to high levels of pollution fell by 66%, which, according to the environment minister, Maisa Rojas, means the 7.5 million residents of the metropolitan region \u201care breathing cleaner air\u201d.<\/p>\n This is not just a bump, it is a sustained trend, the result of long-term policies such as modernising public transportation, implementing vehicle restrictions, and banning wood-burning heaters in winter. But experts say the challenge is far from over: while fine particulate matter (PM2.5) has been decreasing in the cold months, another pollutant \u2013 tropospheric ozone \u2013 gains ground in summer, a scenario worsened by the climate crisis.<\/p>\n \u201cWe\u2019ve been implementing mitigation measures for almost 30 years, and it\u2019s good to see that they are bearing fruit. Critical events are becoming less frequent. But one might expect that after so much time, they would no longer exist. That\u2019s what we want as researchers, citizens and parents: to breathe clean air,\u201d says Nicol\u00e1s Huneeus, a researcher at the Center for Climate and Resilience Research at the University of Chile<\/a>, who celebrates the progress but is not satisfied.<\/p>\n Santiago is often compared to a pressure cooker, partly due to its geography: the Andes form a barrier that makes horizontal dispersion of pollutants difficult. The wind simply has nowhere to go. And another factor makes things worse: temperature inversion. \u201cThe city is warm, but higher up it\u2019s even warmer, so the air in the city doesn\u2019t move. In winter, the inversion is worse, and pollutant generation is higher. In short, Santiago has poor ventilation; we\u2019re in trouble,\u201d says the climatologist Ra\u00fal Cordero, a former member of Chile\u2019s scientific advisory committee on climate change and now a researcher at the University of Groningen.<\/p>\n View of smog over Santiago in 2018. Photograph: Claudio Reyes\/AFP\/Getty Images<\/p>\n Other factors are the atmospheric boundary layer, which determines the volume in which pollutants are diluted. In Santiago, this layer is lower in winter (400\u2013600 metres) than in summer (1,200 metres), increasing particle concentrations. Into this, you put the emissions from transportation and the residential sector, with firewood historically the main heating fuel, and it is easy to understand how Santiago is, at times, one of the most polluted cities in the world. In the worst years, there would be hundreds of critical alerts and environmental emergencies declared as a result of the pollution, and hospitals would be overwhelmed. Felipe Pe\u00f1aloza, a nutritionist who lives in downtown Santiago, refers to \u201cthe constant black cloud that covers the city, which only disappears briefly after rain, but which remains a classic image of Santiago\u201d.<\/p>\n Over the last few years the local government has taken a number of steps. During pre-emergencies and environmental emergencies, wood-burning and wood-based heaters (except certified pellet stoves) are banned, agricultural burning is suspended, and people are encouraged to use public transport.<\/p>\n Vehicle restrictions are also applied: during alerts, cars with licence plates ending in certain digits are banned from circulation; during pre-emergencies, the restrictions expand, affecting more digits and including green-seal vehicles (electric or hybrid, and gasoline or diesel cars meeting Euro 5 or 6 standards). In emergencies, traffic is limited for most vehicles.<\/p>\n Elisa Fern\u00e1ndez, a journalist and resident of \u00d1u\u00f1oa in north-east Santiago, describes herself as \u201cabsolutely compliant\u201d with the law. Her car, which was manufactured before 2010, must be off the road one day a week between May and August. Driving it on restricted days can result in a fine of about \u00a3125. \u201cPrimarily, it\u2019s for economic reasons, but also to contribute to cleaner air,\u201d she says.<\/p>\n This year compliance improved: more than 312,000 vehicles stayed off the road during winter, and violations fell nearly 23%, from 1,900 to 1,600 per day. But Cordero says real progress is coming from modernising and electrifying public transport: 30% of a 9,000-unit fleet is now electric, while targeted traffic restrictions help ease pollution peaks.<\/p>\n Home heating and cooking electrification still lag, mainly due to limited financial support. Huneeus warns of a \u201crebound effect\u201d: some users who switch to pellet stoves return to wood for economic reasons or perceived lower efficiency. This reflects \u201cenergy poverty\u201d and limits the effectiveness of mitigation policies. Nevertheless, violations of the wood-burning ban fell sharply \u201388% lower than in 2024.<\/p>\n Agricultural burning also decreased, with official data showing a 23.8% reduction in the number of fires and a 77% drop in the burned area.<\/p>\n skip past newsletter promotion<\/a><\/p>\n The planet’s most important stories. Get all the week’s environment news – the good, the bad and the essential<\/p>\n Privacy Notice: Newsletters may contain information about charities, online ads, and content funded by outside parties. If you do not have an account, we will create a guest account for you on theguardian.com<\/a> to send you this newsletter. You can complete full registration at any time. For more information about how we use your data see our Privacy Policy<\/a>. We use Google reCaptcha to protect our website and the Google Privacy Policy<\/a> and Terms of Service<\/a> apply.<\/p>\n after newsletter promotion<\/p>\n The result? This year, between May and August \u2013 the period with the worst ventilation conditions\u2014 there were 23 critical episodes, 20 environmental alerts, and 3 pre-emergencies for PM2.5. For perspective, in 2015 there were 915 hours of critical episodes for this pollutant.<\/p>\n Cordero notes an unexpected consequence: the normalisation of pollution. \u201cTwenty years ago, pollution levels were so severe they overwhelmed hospitals in winter. Today, critical episodes have fallen so much that pollution is no longer a public discussion in Santiago,\u201d he says. This makes advancing further measures, such as electrifying homes, more difficult when the problem seems tolerable.<\/p>\n But there is real gratitude for the changes. Mar\u00eda Florencia Salazar says her daughter\u2019s health has improved. \u201cThis helps me a lot, especially because I have a three-year-old daughter. This year, we have had slightly fewer cases of respiratory viruses.\u201d Comparing her hospital visits, she says her daughter has been healthier than last winter and, above all, much better than in 2023.<\/p>\n And Valentina Exp\u00f3sito, a functional training and yoga instructor, says she has noticed it too: \u201cThe air quality this year was better compared to previous years, I felt that there were fewer alerts and pre-emergency days. Even so, smog and pollution are still noticeable \u2013 probably less than before \u2013 but it\u2019s hard to perceive the change unless it is more radical.\u201d<\/p>\n For her, the critical episodes directly affect her work. \u201cWhat affects me the most is how I plan my classes for those days, understanding that more intense physical activity isn\u2019t ideal,\u201d she adds.<\/p>\n Santiago\u2019s winter success is the result of decades of policies and citizen cooperation. But the city still has work to do to ensure this breath of fresh air becomes a lasting change.<\/p>\n","protected":false},"excerpt":{"rendered":"In Santiago, this winter was different. 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