As has been widely reported, New Delhi, India, where air quality is generally a problem, has been suffering through several days of extreme choking toxic smog, exacerbated by a lack of wind at ground level, colliding winds in the upper atmosphere, cooling temperatures, biomass burning in fields and street fires for warmth. For a period of several days, the Air Quality Index calculated by the US Embassy in New Delhi exceeded the 500 level, at one point (8 November, 4 pm) spiking to 1010. Values above 500 are considered “Beyond the AQI”, and are extremely hazardous.
The US Embassy and Consulates’ air quality monitors measure airborne PM2.5 on the compounds of the Embassy and Consulates in several Indian cities, New Delhi among them. Because data from a single monitoring station cannot be applied to an entire city, the air quality data collected at the US Embassy and Consulates may differ from other monitors located in the same cities—however, the data does provide some localized insight into conditions.
The air quality data collected by the US Mission in India is processed by the US Environmental Protection Agency’s (EPA) NowCast algorithm. This algorithm converts raw PM2.5 readings into an air quality index (AQI).
The chart above plots the AQI data, along with the raw PM2.5 concentrations in µg/m3 on an hourly basis from 1 November through 9 November. Annual and daily data is also available from the US Mission.
EPA has assigned a specific color to each AQI category.