Delhi has been grappling with air pollution for more than 25 years. But it has not come to grips with it. The National Capital Region (NCR) has the worst air quality in the world. Stage III of the Graded Response Action Plan (GRAP) was triggered on January 14 as air quality sank into the ‘severe’ category—the worst of six gradations, with the Air Quality Index (AQI) going beyond 450.

AQI measures the concentration of six pollutants in the air: carbon monoxide, ozone, nitrous oxide, and two kinds of microscopic dust particles called Particulate Matter (PM) — 2.5 and 10. When the air turned severely bad, older petrol cars and diesel vehicles that did not make the cut on emissions were parked compulsorily and construction activity was disallowed. This was the third time this winter season that the restrictions were imposed, the first lasting 27 days in November and the second 11 days in December.

The extremely poor air quality of Delhi raises the question of whether the capital of India will continue to grow or its growth will hit the environmental barrier.

As a growth centre, Delhi has many things going for it. The capital territory contributed 4% of India’s GDP in inflation-adjusted prices over the past seven years, while having 1.52% of the country’s population. Its per capita income at ₹4.45 lakh is two and a half times the national average, though there are a large number of people at the edge of poverty. In the past seven years it has grown at an average pace of 4.75% — but in five of those years, national GDP grew faster.