Unmasking India's Air Quality Index: The Controversy Behind the 500 Cap

Sun Nov 16 2025 06:04:06 GMT+0200 (Eastern European Standard Time)

As pollution levels in northern India frequently exceed alarming thresholds, the debate intensifies over why the country's air quality measurement standard is capped at 500. This examination reveals potential misinformation and gaps in public health awareness.

The Air Quality Index (AQI) in India is capped at 500, leading to confusion and concern among the public. While government monitors show levels up to this limit, private monitors indicate numbers soaring above 600 and even 1,000. Experts argue that the upper limit was set to avoid panic and that it fails to accurately reflect the seriousness of the situation. This article explores the implications of this discrepancy and the need for a reevaluation of India's air quality monitoring standards.

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 entirely 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.

But private and international trackers such as IQAir and open-source monitoring platform AQI routinely show far higher numbers, often shooting past 600 and even crossing 1,000 on some days.

This contradiction leaves people asking the same question every year: Which numbers should they trust? And why doesn't India officially report air quality beyond 500?

India's official air-quality scale shows readings above 200 pose clear breathing discomfort to most people on prolonged exposure. Readings above 400 and up to 500 are classified as 'severe' and affect healthy people while also seriously impacting those with existing diseases. The scale however does not go beyond 500 - a cap set more than a decade ago when the National Air Quality Index was launched.

So why was that threshold introduced? 'It was assumed that the health impact would be the same no matter how much higher it goes because we had already hit the worst,' explains Gufran Beig, founder director of SAFAR.

He admits that the 500 cap was originally set to avoid creating panic as crossing that mark signalled an alarming situation requiring immediate mitigation. But this approach effectively flattens the data - anything above 500 is treated the same on official monitors, even if the real concentration is far higher.

According to experts, there's no universal AQI formula. Assessments differ across countries and organizations, leading to potential misunderstandings when comparing international standards with the Indian context.

Ultimately, the current AQI ceiling symbolizes more than just a number; it reflects a system in need of revision in light of ongoing pollution challenges and technological advancements in air quality monitoring.