Delhi Pollution: Why PM2.5 matters more than the AQI

Delhi Pollution: Different regions and organisations calculate AQI differently, which can result in vastly different numbers. However, one consistent measure across all systems is PM 2.5, the fine particulate matter that poses the most serious risks to human health.

Why PM 2.5 matters

PM 2.5 refers to particulate matter that is 2.5 micrometres or smaller in diameter. These particles are so tiny they can penetrate deep into your lungs and even enter your bloodstream. The impacts are devastating, both in the short term (triggering respiratory issues, asthma, and heart attacks) and the long term (causing chronic respiratory diseases, cancer, and reduced life expectancy).

In fact, PM 2.5 is often called the most dangerous pollutant because it acts as a cocktail, carrying toxic chemicals and metals. When discussing air quality, it’s critical to prioritise PM 2.5 levels over general AQI scores because they provide a direct measurement of pollutant concentration rather than an index value that can vary depending on calculation methods.

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AQIs vs. PM 2.5: A useful analogy

To understand the difference, consider stock market indices like Sensex or Nifty. These indices may show different values, but they reflect very similar underlying stock prices.

Similarly, AQIs can differ depending on methodology, but PM 2.5 readings remain consistent as they are based on actual pollutant concentrations or emissions.

So let’s always remember to:

Compare PM 2.5

When analysing air quality, use PM 2.5 levels as your baseline for comparison rather than relying on AQI values, which can be inconsistent.

Monitor health impacts

Keep in mind that even slight increases in PM 2.5 can lead to severe health consequences. No level of air pollution is safe. Studies show that even at low levels (below 150 μg/m³), every 10 μg/m³ increase in PM 2.5 is associated with a significant rise in mortality rates, exposing the danger it poses even before reaching visibly hazardous levels.

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Advocate for transparency

Push for air quality systems to clearly communicate PM 2.5 levels alongside AQI scores for better public understanding.

By prioritising PM 2.5, we focus on what truly matters—the quality of the air we breathe and its direct impact on our health.