Pollution board mulls raising monitoring cap after readings go blank

Why in News

The Central Pollution Control Board (CPCB) is reviewing how it handles extreme particulate matter readings after several Delhi monitoring stations showed data gaps following Deepavali. The system treated hourly readings above 1,000 µg/m³ as out of range and excluded them from the calculation.

Prelims Pointers

• 500 is the ceiling of the reported National Air Quality Index (NAQI). The index is unitless. 1,000 µg/m³ was the upper limit of the particulate matter concentration range used for data validation.

• The index uses eight pollutants.

1. Particulate matter: PM 2.5 and PM 10.

2. Gases: carbon monoxide, nitrogen dioxide, sulphur dioxide, ground-level ozone and ammonia.

3. Metal: lead.

• A station needs sufficient data for at least three pollutants, including PM 2.5 or PM 10.

Prelims Traps

• “Carbon dioxide and methane are among the gases used to calculate India’s AQI.” This is incorrect. The index includes carbon monoxide, nitrogen dioxide and sulphur dioxide. (UPSC Prelims 2016)

• “The World Health Organization (WHO) recommends the same PM 2.5 concentration for the 24-hour and annual means.” This is incorrect. Its guidelines recommend 15 µg/m³ for the 24-hour mean and 5 µg/m³ for the annual mean. (UPSC Prelims 2022)