The ambient air quality standard for PM2.5 (24-hour average) as per National Ambient Air Quality Standards (NAAQS 2009, CPCB India) is:

• A 25 µg/m³
• B 40 µg/m³
• C 60 µg/m³ ✓
• D 100 µg/m³

Explanation

India's NAAQS (2009) sets PM2.5 at 60 µg/m³ for 24-hour average and 40 µg/m³ as the annual average. The WHO 2021 guideline has PM2.5 at 15 µg/m³ (24-hour) and 5 µg/m³ (annual) — far stricter than India's standards. PM10 24-hour NAAQS is 100 µg/m³. The higher Indian limits reflect technological and socioeconomic constraints, not a different understanding of health effects.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.