We Need to Work Hard to Catch up with WHO’s Safe AQ Limit

In 2019, the United Nations General Assembly designated September 7 as the ‘International Day of Clean Air for Blue Skies, underscoring a growing global commitment to clean air. That time India ranked third globally in terms of pollution, and its average PM_2.5 concentration was 54.4 µg/m³ in 2023, which is more than 10 times the WHO’s safe limit.

In line with the global movement, this year also India celebrated ‘Swachh Vayu Divas’ on September 7, in Jaipur. During the event, it was highlighted that focused actions and effective resource convergence have resulted in positive outcomes under the National Clean Air Programme (NCAP), with air pollution levels declining in 95 cities. Remarkably, 51 of these cities under NCAP have achieved reductions in PM₁₀ levels of over 20% compared to the baseline year of 2017-18, and 21 cities have reported reductions exceeding 40%.

Before going further, we need to understand the difference between PM_2.5 and PM₁₀. As per United States Environment Protection Agency (EPA): PM₁₀ means inhalable particles, with diameters that are generally 10 micrometers and smaller; and PM_2.5 means fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller. PM_2.5 particles are the main cause of reduced visibility – as well as if their level goes to or above 35 μg/m³ during a 24-hour period, the air is considered unhealthy.

Now, the Indian Monthly Ambient Air Quality Snapshot by the Centre for Research on Energy and Clean Air (CREA) states that – in September 2024, a total of 201 Indian cities were categorised as ‘Good (0-30 µg/m³)’ on the PM_2.5 Air Quality Index (AQI) scale, while 59 cities were ‘Satisfactory (31-60 µg/m³)’ and 4 cities were ‘Moderate (61-90 µg/m³)’.

WHO guidelines state that annual average concentrations of PM_2.5 should not exceed 5 µg/m³, while 24-hour average exposures should not exceed 15 µg/m³ more than 3 – 4 days per year. Thus, the bottom line is – we need not be cheerful to see the reduction in PM₁₀ level, instead we will have to work meticulously to bring the overall PM_2.5 level within the WHO’s specified safe level.

Pravita Iyer
Publisher & Director