Air quality is reported as a number for today. Exposure is what a year of those numbers adds up to. This page pulls hourly PM2.5, PM10, nitrogen dioxide and ozone for any place in India from Open-Meteo's air quality service, and reports the year the way an epidemiologist would read it: the annual mean against the WHO guideline and India's own standard, how many days breached the 24-hour limits, the cumulative dose in cigarette equivalents, and which months did the damage.
Place and period
The archive runs from mid-2022. A full year is the meaningful unit; the WHO and Indian annual limits are annual means.
Limits used
| Pollutant | WHO 2021 | India NAAQS 2009 |
|---|---|---|
| PM2.5 annual | 5 | 40 |
| PM2.5 24-hour | 15 | 60 |
| PM10 annual | 15 | 60 |
| PM10 24-hour | 45 | 100 |
| NO₂ annual | 10 | 40 |
| NO₂ 24-hour | 25 | 80 |
µg/m³. WHO Global Air Quality Guidelines (2021); Indian National Ambient Air Quality Standards notified 18 November 2009.
The year
How the numbers are made
Hourly concentrations come from Open-Meteo's air quality API, which serves the Copernicus CAMS global and European models re-analysed and forecast on a grid of roughly 11 km; they are model estimates rather than station readings, and they run smoother than a CPCB monitor next to a road. Daily means are the mean of the 24 hourly values; a day counts as breaching a 24-hour limit when its daily mean exceeds it. The cigarette equivalent uses the Berkeley Earth rule of thumb that a day at 22 µg/m³ of PM2.5 is comparable in mortality risk to one cigarette, so the year's equivalent is the sum of daily means divided by 22. It is a way of communicating a dose rather than a dose-response model.