# SmogRank

> Rankings of the world's cities by fine-particle air pollution (PM2.5), from ground monitors, updated hourly, with every past day, week, month and year kept.

- [Current ranking](https://smogrank.com/): last 24 hours; ?w=7d, 30d or year for other windows
- [All cities](https://smogrank.com/rankings)
- Other ways to rank: ?by=days (share of measured days over 35.4 µg/m³, unhealthy) and ?by=people (population times that share) on the 30-day and year-to-date boards and on past months and years, e.g. https://smogrank.com/rankings?w=30d&by=days; ?by=peak (a city's worst 6 hours, read by two sites 3 km or more apart) where a board offers it
- [World map and countries](https://smogrank.com/world): continents at /world/{asia, europe, africa, north-america, south-america, oceania}; the page's "Explore the map" opens the live map: every measured city with the day's fires, smoke and volcanic ash, the last week hour by hour, and every city day by day since January 2023
- [Explore](https://smogrank.com/explore): every way to explore the measurements, listed below
- [Past rankings](https://smogrank.com/history): /history/YYYY, YYYY-MM, YYYY-Www, YYYY-MM-DD; with the air calendar, every measured country's typical city week by week since 2023
- [The race](https://smogrank.com/history/race): countries by their typical city over 30 days (?w=7d for 7), day by day since 2023, as a bar-chart race; ?k=cities for the 40 worst cities, &in={country code} for one country's, e.g. https://smogrank.com/history/race?k=cities&in=in
- [Cleaner or dirtier](https://smogrank.com/changes): every measured city's PM2.5 against the same days a year earlier, biggest rise first; ?year=YYYY for a finished year, ?in={country code} for one country, e.g. https://smogrank.com/changes?in=in
- [Compare two cities](https://smogrank.com/compare): pick any two measured cities, or go straight to https://smogrank.com/compare/{country code}-{city}/{country code}-{city}, the pair in alphabetical order, e.g. https://smogrank.com/compare/in-delhi/pk-lahore: means, months, years and worst days, on the days both cities measured in the last year
- [Bad-air episodes](https://smogrank.com/episodes): smoke, smog and haze events found in the measurements, each with its cities, map and day-by-day spread; the newest year's list, ?year=YYYY for others, ?in={country code} for one country; as an Atom feed at https://smogrank.com/episodes.atom (same ?in=)
- City bad-air days as Atom: https://smogrank.com/{country code}/{city}.atom (days of 35.5 µg/m³ or more in the last year)
- Country boards: https://smogrank.com/{country code}, e.g. /in; past months and years at /{country code}/history/YYYY or YYYY-MM, e.g. /in/history/2025-11
- Region boards (states, provinces): https://smogrank.com/{country code}/region/{region}, e.g. /us/region/california; past months and years at /{country code}/region/{region}/history/YYYY or YYYY-MM
- City pages: https://smogrank.com/{country code}/{city}, e.g. /us/los-angeles: PM2.5 now, why it ranks where it does, its ranks, the last 12 months and its bad-air episodes
- A city's months: https://smogrank.com/{country code}/{city}/history, e.g. /in/delhi/history: every month since its first measured day, each year's mean, days measured and world rank, its worst months and days
- [Find a city](https://smogrank.com/search?q=delhi): /search?q={name}
- [Air quality scales](https://smogrank.com/scales): PM2.5 in µg/m³ on every scale we show (US AQI, India AQI, China AQI, the European index, UK DAQI, Canada AQHI+) on one chart, with a converter: ?ug={µg/m³}, or ?from={us|in|cn|uk|ca}&i={index}; a page per scale at /scales/{us|in|cn|eu|uk|ca} with its bands and how many cities are in each now
- [How we rank](https://smogrank.com/methodology)
- [Sources and licences](https://smogrank.com/sources)
- MCP server (free, rate-limited; Streamable HTTP): https://smogrank.com/mcp, tools find_city, city_air, city_history, rankings