Understanding India's Pollution Threshold: The 500 AQI Cap

Sun Nov 16 2025 05:47:37 GMT+0200 (Eastern European Standard Time)

Despite alarming air quality readings, India's official air quality index caps at 500, leaving citizens confused about the true extent of pollution. Experts discuss the implications of this threshold and propose necessary reforms.

In northern India, air pollution has reached unprecedented levels, yet official air quality readings are capped at 500, sparking debates over the accuracy and efficacy of India's pollution reporting system. This limit, set over a decade ago, was aimed at preventing public panic but raises questions about its relevance today. Experts argue for a revision of the National Air Quality Index to reflect real-time conditions and health impacts, emphasizing the need for updated monitoring technology to guide effective public health responses.

For millions across northern India, the November air tastes ashy, the sky looks visibly hazy and merely stepping outside feels like a challenge.

For many, their morning routine starts with checking how bad the air is. But what they see depends on which monitor they use.

Government-backed apps like SAFAR and SAMEER top out at 500 - the upper limit of India's AQI (air quality index) scale, which converts complex data on various pollutants such as PM2.5, PM10, nitrogen dioxide, sulphur dioxide, carbon monoxide and ozone, into a single number.

However, private and international trackers such as IQAir and open-source monitoring platform AQI routinely show far higher numbers, often surpassing 600 and even crossing 1,000 on some days. This contradiction leads many to question which data should be trusted, and why India does not officially report air quality beyond 500.

India's official air-quality scale shows readings above 200 pose clear breathing discomfort to most people, while those reaching up to 500 are classified as severe. The scale has not included numbers beyond 500 since the National Air Quality Index was launched over a decade ago. Experts argue this cap was originally intended to avoid public panic, but now it flattens the data and obscures the severity of pollution.

Though officials believe health impacts remain consistent above this threshold, they admit it lacks flexibility to account for worsening conditions. Global platforms do not face the same limitations, which is why they report much higher figures.

The disparity extends to how hazardous air is defined. The World Health Organization (WHO) considers PM2.5 levels above 15 micrograms per cubic meter as hazardous, while India sets the bar at 60. Experts emphasize that the absence of a universal AQI formula complicates comparisons with international standards.

Furthermore, differences in technology also play a role. India's pollution monitoring relies on specific Beta Attenuation Monitors (BAMs) while platforms like IQAir use sensor-based monitors, which are less accurate. As India's pollution control framework remains stagnant since 2009, experts call for comprehensive revisions, urging removal of the AQI cap, aligning with scientific insights about health effects as pollution levels rise.

Ultimately, the limitation of India's AQI at 500 serves more as a systemic ceiling rather than a reflection of actual air quality, necessitating updates to effectively safeguard public health.