Air quality history

How to read it

The map and chips show one snapshot per year. Colours follow the WHO interim targets: emerald is at or below the 5 µg/m³ annual guideline, lime is up to 10, yellow to 15, orange to 25, red to 35, purple to 50, maroon above. Long-term exposure above roughly 25 µg/m³ raises cardiovascular and respiratory risk, so anything orange and above is worth weighing when picking a base.

Solid cells in the table use modelled population-weighted estimates from Our World in Data (sourced from IHME's Global Burden of Disease). Those are the most credible numbers but lag the calendar by a year or two. Italic cells use a station-mean from OpenAQ's sensor network, which closes the gap for the most recent year and the current year-to-date. Methodology differs between the two, so watch for visible step changes at the seam.

Bali is not in the data because the underlying sources are country-level only. Indonesia's value applies to the island.

Why PM2.5 specifically

PM2.5 is the fraction of airborne particulate matter small enough to slip past the nasal filter and lodge deep in the lungs and bloodstream. Of every air-quality metric collected by the major networks, it has the strongest link to chronic disease outcomes, so it is the headline number behind every AQI app. A peak haze-week reading of 200 µg/m³ in Chiang Mai or Hanoi is unpleasant. A multi-year average of 30 µg/m³ is what shapes your long-term health.

Updates

The dataset rebuilds automatically with the rest of the site's daily pipeline: OWID gets refetched in case a new vintage has been published, and OpenAQ aggregates roll forward to the current month. You shouldn't need to touch this manually. For a live station view at any specific city, see the news and country pages: Thailand, Vietnam, Indonesia, Philippines, Malaysia, Cambodia, Laos, Bali.