The toxic night of lights: Understanding Diwali and its air and noise pollution

Every Diwali, the glowing lights across India's cities honour the timeless triumph of light over darkness. Yet beneath each sparkler and booming firecracker lies the harsh truth is written in the very air we breathe. Across the metro cities of India, the festival of lights too often signals a spike in pollution so steep it now routinely surpasses safety thresholds many times over. As the Supreme Court of India in October 2025 allowed limited use of certified "green" crackers under strict conditions, the question looming over us: can tradition be honoured without compromising our children's lungs, our elders' health and the environment that sustains us?

- DR SINGARAM KULANDAIVEL

A Night Like No Other

When the first firecracker arcs across the Delhi sky, or the first fountain glows in a Bengaluru lane, it is celebration in full display. But so too is a surge in fine particulate pollution. Data from multiyear monitoring across Indian metros show that between about 7-9 pm on Diwali nights, particulate matter of diameter 2.5 microns (PM2.5) begins to climb-often 3-4 times the pre-bursting value. In cities like the national capital, these numbers have spiked to several hundred micrograms per cubic meter in just a few hours. The same air that carries our festive cheer becomes laden with toxins, triggering breathlessness, cough, and disease.

The meteorological factors like still nights, weak winds, low mixing heights-compound the effect, trapping the pollution near ground level. That means what goes up from a firecracker stays down where we breathe. In India's dense urban sprawl, every breath taken and released carries traces of soot, fumes, and fatigue.

Cities under the Lens: Metro Patterns & Hidden Hazards:

Let's take a tour across six major Indian metros (according to a research report from 2024, urban centres like New Delhi, Greater Noida, Ghaziabad, and Faridabad are identified as some of the most polluted cities globally) to see how the story unfolds:

Delhi NCR - The epicenter of pollution. Even in years of bans and partial restrictions, PM2.5 concentrations on Diwali nights in Delhi regularly crossed 800-1,000 µg/m³-about 60 times the World Health Organization (WHO) 24-hour guideline of 15 µg/m³. Competing sources-traffic, industry, stubble-burning in neighbouring states-make the city particularly vulnerable.