About SmogRank

SmogRank ranks the world's cities by how dirty their air is, hour by hour, and keeps every past ranking.

Most air-quality sites show a reading for one place right now. We wanted the other questions answered: which cities are worst this week, this month and this year; where a city stood last November; whether today's haze is normal for it or a one-off. So we built continuous leaderboards from ground monitors, with the history kept and each city's pattern explained from its own data.

The numbers are fine-particle pollution (PM2.5), the pollutant most tied to health harm, from government and research monitors published through OpenAQ. How we rank explains every rule; Data sources credits each provider.

SmogRank is run by Buretto from British Columbia, Canada. Corrections and questions: hello@smogrank.com.