The World Health Organization (WHO) has set air quality guidelines to limit exposure to key air pollutants, measured in micrograms per cubic meter (µg/m³). The main pollutants include:
- PM2.5: 5 µg/m³ (annual mean) and 15 µg/m³ (24-hour mean)
- PM10: 15 µg/m³ (annual mean) and 45 µg/m³ (24-hour mean)
- Nitrogen dioxide (NO₂): 10 µg/m³ (annual mean) and 25 µg/m³ (24-hour mean)
- Ozone (O₃): 100 µg/m³ (8-hour mean)
- Sulfur dioxide (SO₂): 40 µg/m³ (24-hour mean)
These pollutants are measured using sensors that detect concentration in the air.
Air pollution and its potential impact on health is measured in terms of a numerical scale called Air Quality Index (AQI). The AQI typically ranges from 0 to 500, with higher values indicating worse air quality. It measures key pollutants such as PM2.5, PM10, ozone (O₃), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and carbon monoxide (CO).
AQI categories:
- 0-50: Good
- 51-100: Moderate
- 101-150: Unhealthy for sensitive groups
- 151-200: Unhealthy
- 201-300: Very unhealthy
- 301-500: Hazardous
