Delhi’s Humidity Could Lead to Underestimation of Pollution by Up to 20%, Study Finds

Fresh studies suggest Delhi's maximum winter humidity can result in a catastrophic underestimate of air pollution levels. Fine particulate matter (PM1) was observed to be extracting humidity from the air, which resulted in up to 20% underestimating pollution levels, according to npj Clean Air journal research. The research goes on to raise the importance of more accurate measurements of air quality in the world's most polluted megacity.

How Humidity Affects Air Pollution Estimates:-
The research, conducted by a team of scientists at the University of Birmingham, UK, investigates hygroscopic growth, which is a process where fine particulate matter grows in size by absorbing water from humid air. This influences the operation of air quality monitoring equipment, leading to possible errors in estimating pollution. The study concentrated particularly on PM1 particles, which have a size smaller than one micron and are severe health issues since they can penetrate deep into the lungs and enter into blood circulation.

It is worst in Delhi, which the 2024 World Air Quality report done by IQAir most recently ranked as the filthiest capital city in the world. The largest underestimation of pollutants occurs at its peak morning hours in December and January when there is maximum humidity. The study estimates that PM1 is being underestimated by a maximum of 50 micrograms per cubic meter, or an estimated 20% underestimation of the pollution.

Seasonal Patterns of Underestimation of Pollution
It was confirmed by the research that humidity's impact on pollution estimation varies in various seasons.

Winter (December–January): The greatest underestimation occurs during rush hours in the morning with high humidity and high pollution.
Spring (February–March): The second highest overestimation above 8.5% is when relative humidity is around 80%.
Monsoon (Jul–Sep): There is virtually no biasness in the measurement of pollution because there is strong rain that clears out puffed up pollutant particles.
Summer (Apr–Jun): It is minimum because low-humidity weather does not provide a setting where the pollutant particles would be able to soak much water.

Implications for Air Quality Monitoring:-
The study suggests that the emission of hygroscopic particles, particularly those released from domestic and biomass burning sources, are mostly accountable for overestimation of the pollution level. The particles have extremely high chlorine loads and a high ability to absorb water and therefore compromise the accuracy of air quality estimations. Controlling the emissions from these sources can help to make pollution estimates more accurate and lead to more efficient reduction strategies.

The research also requires further observation of PM2.5 and PM10 levels in order to improve the knowledge on air pollution in New Delhi. The policymakers could utilize the research to strengthen pollution control and air quality monitoring, leading to more efficient public health policies.

Need for More Accurate Pollution Assessments:-
Delhi’s air pollution remains a severe public health crisis, and underestimating PM1 levels could mean that residents are exposed to even higher pollution levels than officially recorded. The study emphasizes the need for advanced monitoring techniques that account for hygroscopic growth, particularly during winter months when pollution is at its worst.

As Delhi grapples with poisonous air, greater precision is needed to deploy targeted pollution control strategy. By enhancing flaws in current methods of air quality measurement, scientists hope to assist in advancing more precise ways of measuring pollution and public health policy.

Source: npj Clean Air, IQAir, University of Birmingham