Why Delhi’s PM2.5 Levels Dropped Rapidly Post-Diwali After Hitting a 4-Year High

Delhi’s air quality crisis is an annual ordeal, but this Diwali season brought an especially severe spike. On November 12, 2023, PM2.5 levels surged to a four-year high, exceeding 999 µg/m³ in some areas—nearly 20 times the WHO’s safe limit. Yet, within days, pollution levels dropped sharply. What caused this dramatic shift? Here’s the breakdown.

The Diwali Pollution Peak: Why Air Turned Toxic

Firecrackers—despite bans—were a major contributor. Delhi’s AQI entered the “severe plus” category as millions lit fireworks, worsening pollution from stubble burning in Punjab and Haryana. Weather worsened the crisis:

• Low wind speed trapped pollutants near the ground.
• High humidity thickened the smog, reducing visibility.

Why PM2.5 Levels Dropped Suddenly

By November 15, PM2.5 levels had fallen below 200 µg/m³ in some areas. Key reasons:

1. Stronger Winds Cleared the Air

• The wind direction shifted from northwest to southeast, bringing cleaner air.
• Higher wind speeds (5–12 km/h) dispersed pollutants faster.

2. Rain and Western Disturbances Helped

• Light rainfall (November 14–15) settled dust and washed away particulates.
• A western disturbance (storm system from the Mediterranean) improved air circulation.

3. Fewer Farm Fires Post-Diwali

• Stubble-burning incidents dropped by 30% in Punjab and Haryana, reducing smoke inflow.

4. Emergency Measures (GRAP Stage IV) Had Limited Impact

• Construction bans and diesel generator restrictions likely helped marginally.

Did Policy Actions Make a Difference?

While firecracker bans and GRAP were in place, nature played the biggest role. This shows Delhi’s reliance on weather rather than policy for clean air.

Long-Term Solutions Needed

This episode reveals Delhi’s reactive (not preventive) approach to pollution. For lasting change, the city needs:

✔ Stricter year-round enforcement of pollution norms.
✔ Scaled-up farmer incentives to stop stubble burning.
✔ Expanded public transport (metro, EVs) to cut vehicular emissions.

Conclusion: A Temporary Respite

Delhi’s post-Diwali air cleanup was more luck than policy success. Without systemic fixes, the toxic haze will return—leaving citizens at the mercy of the wind.

For real-time updates on India’s environmental challenges, follow ThePrint.