Q.Describe the key points of the revised Global Air Quality Guidelines (AQGs) recently released by the World Health Organisation (WHO). How are these different from its last update in 2005? What changes in India’s National Clean Air Programme are required to achieve revised standards?

Body

graph TD
    WHO["Revised WHO Guidelines"] --> PM["Particulate Matter (PM2.5 and PM10)"]
    WHO --> O3["Ozone (O3)"]
    WHO --> NO2["Nitrogen Dioxide (NO2)"]
    WHO --> SO2["Sulfur Dioxide (SO2)"]
    WHO --> CO["Carbon Monoxide (CO)"]

    PM --> PM25_Ann["PM2.5 Annual Mean: 5 µg/m³"]
    PM --> PM25_24h["PM2.5 24-Hour Mean: 15 µg/m³"]
    PM --> PM10_Ann["PM10 Annual Mean: 15 µg/m³"]
    PM --> PM10_24h["PM10 24-Hour Mean: 45 µg/m³"]

    O3 --> O3_8h["8-Hour Mean: 100 µg/m³"]

    NO2 --> NO2_Ann["Annual Mean: 10 µg/m³"]
    NO2 --> NO2_24h["24-Hour Mean: 25 µg/m³"]

    SO2 --> SO2_24h["24-Hour Mean: 40 µg/m³"]

    CO --> CO_24h["24-Hour Mean: 4 mg/m³"]

Key Points of the Revised WHO AQGs & Comparison with 2005 Standards

The 2021 guidelines significantly lowered the acceptable limits for six major criteria pollutants compared to the 2005 levels:

1. Particulate Matter ($PM_{2.5}$):
   • Annual Mean: Reduced from $10 μg/m^3$ to $5 μg/m^3$.
   • 24-Hour Mean: Reduced from $25 μg/m^3$ to $15 μg/m^3$.
2. Particulate Matter ($PM_{10}$):
   • Annual Mean: Reduced from $20 μg/m^3$ to $15 μg/m^3$.
   • 24-Hour Mean: Reduced from $50 μg/m^3$ to $45 μg/m^3$.
3. Nitrogen Dioxide ($NO_2$):
   • Annual Mean: Drastically reduced from $40 μg/m^3$ to $10 μg/m^3$.
   • 24-Hour Mean: Established at $25 μg/m^3$.
4. Sulfur Dioxide ($SO_2$):
   • 24-Hour Mean: Stricter limit of $40 μg/m^3$ (previously $20 μg/m^3$ in 2005, but revised to reflect short-term exposure risks).
5. Ozone ($O_3$):
   • 8-Hour Mean: Maintained at $100 μg/m^3$.
6. Carbon Monoxide (CO):
   • 24-Hour Mean: Set at $4 mg/m^3$.

Required Changes in India's National Clean Air Programme (NCAP)

India's current National Ambient Air Quality Standards (NAAQS) are much more relaxed than the WHO guidelines (e.g., India's annual limit for $PM_{2.5}$ is $40 μg/m^3$). To align with the new global standards, the NCAP must incorporate the following structural changes:

• Tightening Emission Standards: Gradually revise India's NAAQS to bring them closer to the scientific thresholds recommended by the WHO.
• Adopting an Airshed Approach: Shift from city-centric pollution management to regional, airshed-based planning. Air pollution does not respect administrative boundaries; hence, action plans must consider transboundary meteorological and geographical factors.
• Stricter Targets for $PM_{2.5}$ and $PM_{10}$: Under the proposed "Mission - Clean Air for All," the government must set more aggressive reduction targets (beyond the current 20-30% reduction goal).
• Strengthening Monitoring Infrastructure: Expand the network of Continuous Ambient Air Quality Monitoring Stations (CAAQMS), particularly in rural and semi-urban areas.
• Focus on Multi-Sectoral Mitigation: Accelerate transition in key polluting sectors by promoting electric mobility, enforcing strict industrial emission norms, and tackling agricultural crop residue burning.