Air pollution in New Delhi is worse than estimated, with a new study revealing that pollution levels are underestimated by up to 20% due to particle swelling.
Published in NPJ Clean Air, the research shows that hygroscopic growth refers to the ability of fine particles to absorb water vapor. This process causes significant measurement errors, especially during humid conditions.
This effect reduces the efficiency of air quality monitors, leading to miscalculations in PM1 levels. The greatest underestimation occurs during winter morning rush hours, when humidity is at its highest.
HOW PARTICLE GROWTH SKEWS POLLUTION READINGS
Fine particles in Delhi’s air swell in humid conditions, making them harder to detect. This means official air quality data fails to reflect the true severity of pollution.
The study highlights:
- Winter mornings (December-January): The highest underestimation, up to 20%, occurs during rush hour (8-9 AM), when humidity reaches 90%.
- Spring (February-March): Pollution levels are underestimated by 8.6%, with humidity around 80%.
- Monsoon season (July-September): Despite high humidity (85%), rainfall washes out particles, minimizing bias.
- Summer (April-June): The driest months, with minimal underestimation due to low humidity (28-50%).
Delhi’s air pollution crisis is already severe, but this new data suggests it is even worse than official records show.
BIASED MEASUREMENTS MASK HEALTH RISKS
New Delhi, the world’s most polluted capital, faces severe air quality issues. The World Health Organization (WHO) reports that Delhi’s PM1 levels are extremely high. They are 24 times higher than safe limits, even based on underestimated data.
Fine particulate matter is the leading air pollutant, responsible for 10,000 premature deaths annually. The study shows that air pollution measurements fail to capture the full health risks, particularly in winter.
HOW BIOMASS BURNING WORSENS POLLUTION
The study identifies biomass burning and residential emissions as key contributors to Delhi’s air pollution. These sources release highly hygroscopic chlorine compounds, worsening particle swelling and increasing pollution underestimation.
Scientists suggest targeting emissions from biomass burning to reduce both pollution levels and measurement bias.
CALL FOR BETTER POLLUTION MONITORING
Dr. Ying Chen, lead author from the University of Birmingham, emphasizes the need for better air quality monitoring. She calls for:
- More in-situ observations of PM2.5 and PM10 for accurate pollution tracking.
- Revised air quality models that account for hygroscopic particle growth.
- Stronger pollution control policies, especially in winter months.
Delhi’s air pollution is already a public health emergency. With new data showing even higher pollution levels than recorded, the urgency to act has never been greater.