Air Quality
- 29 Mar, 2022
Air quality standards are generally health-based guidelines which seek to establish the concentrations of air pollutants to which the public can be exposed throughout their lifetime without significant adverse effects at a population level.
| Pollutant | Type | Standard | Averaging Time | Form | Regulatory Citation |
| Particulate matter (PM10) | Primary and Secondary | 150 μg/m3 | 24-hour | Not to be exceeded more than once per year on average over 3 years | 40 CFR 50.6 |
| Fine particulate matter (PM2.5) | Primary | 12 μg/m3 | annual | Annual mean, averaged over 3 years | 40 CFR 50.18 |
| Secondary | 15 μg/m3 | annual | Annual mean, averaged over 3 years | 40 CFR 50.7 | |
| Primary and Secondary | 35 μg/m3 | 24-hour | 98th percentile, averaged over 3 years | 40 CFR 50.18 | |
| Ozone (O3) | Primary and Secondary | 0.12 ppm (235 μg/m3) | 1-hour | expected number of days per calendar year, with maximum hourly average concentration greater than 0.12 ppm, is equal to or less than 1 | 40 CFR 50.9 |
| Primary and Secondary | 0.070 ppm (140 μg/m3) | 8-hour | Annual fourth-highest daily maximum 8-hour concentration, averaged over 3 years | 40 CFR 50.19 | |
| Sulfur dioxide (SO2) | Primary | 75 ppb | 1-hour | 99th Percentile of 1-hour daily maximum concentrations, averaged over 3 years | 40 CFR 50.17 |
| Secondary | 0.5 ppm (1,300 μg/m3) | 3-hour | Not to be exceeded more than once per year | 40 CFR 50.5 | |
| Carbon monoxide (CO) | Primary | 35 ppm (40 mg/m3) | 1-hour | Not to be exceeded more than once per year | 40 CFR 50.8 |
| Primary | 9 ppm (10 mg/m3) | 8-hour | Not to be exceeded more than once per year | 40 CFR 50.8 | |
| Nitrogen dioxide (NO2) | Primary and Secondary | 0.053 ppm (100 μg/m3) | annual | Annual mean | 40 CFR 50.11 |
| Primary | 0.100 ppm (188 μg/m3) | 1-hour | 98th percentile of 1-hour daily maximum, averaged over 3 years | 40 CFR 50.11 | |
| Lead (Pb) | Primary and Secondary | 0.15 μg/m3 | Rolling 3 months | Not to be exceeded | 40 CFR 50.12 |
Air Quality Index :
An air quality index (AQI) is used by government agencies to communicate to the public how polluted the air currently is or how polluted it is forecast to become. Public health risks increase as the AQI rises. Different countries have their own air quality indices, corresponding to different national air quality standards.
Computation of the AQI requires an air pollutant concentration over a specified averaging period, obtained from an air quality monitor or model. Taken together, concentration and time represent the dose of the air pollutant. Health effects corresponding to a given dose are established by epidemiological research. Air pollutants vary in potency, and the function used to convert from air pollutant concentration to AQI varies by pollutant. Its air quality index values are typically grouped into ranges. Each range is assigned a descriptor, a color code, and a standardized public health advisory.
AQI in India :
