Supreme Court Reviews Delhi Air Quality Monitoring

Supreme Court Inquiry on Delhi Air Quality Monitoring

Air Quality Monitoring in Delhi

• Continuous Ambient Air Quality Monitoring Stations (CAAQMS):
  • Total number: 40
  • Key pollutants measured: PM2.5, PM10, NO₂, SO₂, CO, O₃, NH₃, Pb
  • Operating guidelines: Developed by Central Pollution Control Board (CPCB), 2012.

Measurement Techniques

• Particulate Matter (PM):
  • Measured using Beta Attenuation Monitors (BAM).
• Gaseous Pollutants:
  • SO₂: Measured by UV fluorescence.
  • O₃: Measured by UV photometry.
  • CO: Measured using non-dispersive infrared (NDIR) absorption.
  • NOₓ: Measured via chemiluminescence.
  • NH₃: Measured using optical spectroscopy.
• Standards: Methods approved under National Ambient Air Quality Standards (NAAQS), 2009.

Challenges to Air Quality Index (AQI) Reading Accuracy

• Data Quality Requirements:
  • At least 16 hours of reliable data needed for three pollutants.
  • Failure to maintain this leads to data blackouts.
• Common Issues:
  • Calibration failures, power outages, extreme weather.
  • Influence of local conditions (high humidity affecting particle weight).
• CAG Report Findings:
  • Inadequate pollutant measurement (e.g., lead not monitored by 24 stations).
  • Data generation gaps: Only 12% of months had complete data (April 2014 to January 2021).

Research Insights

• Study Findings:
  • CSIR-NPL study (2021) indicated measurement inaccuracies under high relative humidity (RH > 60%).
  • PM2.5 overestimations could reach 30% to over 5x during pollution spikes.
  • Recommendations for site-specific correction factor to improve measurement accuracy.

Recommendations for Improvement

• CAG Recommendations:
  • Relocate CAAQMS to optimal sites free from obstructions.
  • Ensure all pollutants, including lead, are monitored effectively.
  • Daily calibration and adherence to CPCB protocols are critical.
  • Regular third-party audits suggested for efficacy and reliability.

Stakeholder Comments

• Anumita Roychowdhury, Centre for Science and Environment: Emphasizes the need for ongoing audits to ensure the accuracy of air quality readings.

Key Takeaways

• The Supreme Court is actively overseeing the efficacy of Delhi's air quality monitoring systems amidst growing pollution concerns.
• The CPCB’s framework and recommendations highlight the necessity for continual data integrity and technological upgrades at monitoring stations to ensure public health safety.