Chennai
The air quality data collected by the U.S. Mission in India is translated into actionable information by the U.S. Environmental Protection Agency’s (EPA) NowCast algorithm. This algorithm converts raw PM 2.5 readings into an air quality index (AQI) value that can help inform health-related decisions. The index is calculated based on data over a 3-12 hour period depending on the variability of particulate concentration.
PM 2.5 is a standard recognized by the U.S. Environmental Protection Agency and allows us to compare against U.S. standard measures. For more information on PM2.5 and air quality in general, please visit the EPA’s website. U.S. Mission India does not track other contaminants that contribute to air pollution [e.g. coarse dust particles (PM10), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO)].
If a reading of “-999” appears for any of the U.S. Embassy’s or Consulates’ readings, please disregard it as this indicates that the data is currently unavailable for the site in question.
AQI updates from U.S. Mission India air quality monitors are also now available on a trial basis via the @USAndIndia Twitter feed at 7:30 and 17:30 daily to assist you in planning your day and evening activities.
| Air Quality Index Levels of Health Concern | Numerical Value | Meaning |
|---|---|---|
| Good | 0 to 50 | Air quality is considered satisfactory, and air pollution poses little or no risk |
| Moderate | 51 to 100 | Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution. |
| Unhealthy for Sensitive Groups | 101 to 150 | Members of sensitive groups may experience health effects. The general public is not likely to be affected. |
| Unhealthy | 151 to 200 | Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects. |
| Very Unhealthy | 201 to 300 | Health warnings of emergency conditions. The entire population is more likely to be affected. |
| Hazardous | 301 to 500 | Health alert: everyone may experience more serious health effects. |
