After Decades Of Legendarily Awful Air Pollution, Santiago May Finally Be Turning The Corner

For nearly 30 years Chile’s 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 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 “are breathing cleaner air”. 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 – tropospheric ozone – gains ground in summer, a scenario worsened by the climate crisis.

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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. “The city is warm, but higher up it’s even warmer, so the air in the city doesn’t move. In winter, the inversion is worse, and pollutant generation is higher. In short, Santiago has poor ventilation; we’re in trouble,” says the climatologist Raúl Cordero, a former member of Chile’s scientific advisory committee on climate change and now a researcher at the University of Groningen.

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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. 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.

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Home heating and cooking electrification still lag, mainly due to limited financial support. Huneeus warns of a “rebound effect”: some users who switch to pellet stoves return to wood for economic reasons or perceived lower efficiency. This reflects “energy poverty” and limits the effectiveness of mitigation policies. Nevertheless, violations of the wood-burning ban fell sharply –88% lower than in 2024. 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. The result? This year, between May and August – the period with the worst ventilation conditions— 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.

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https://www.theguardian.com/environment/2025/oct/02/lifting-black-cloud-smog-bound-city-cut-dangerous-levels-air-pollution