Delhi-NCR is facing temperatures near 45 degrees Celsius. Yet, heat is not the only concern now. Authorities have recognised that pollution has returned in a serious way. The Commission for Air Quality Management imposed Stage 1 of GRAP on Tuesday, May 19, 2026. The move came after air quality slipped into the “poor” category. Forecasts also suggested that poor air may continue for the next few days.
AQI Numbers Show Regional Stress
According to the Central Pollution Control Board, Delhi recorded an AQI of 208 on Tuesday. Noida stood at 233, while Ghaziabad reached 247. Greater Noida saw a much worse AQI of 312. Gurugram performed slightly better with 178. Across most places, PM10 emerged as the main pollutant. However, Gurugram showed both PM10 and PM2.5 as equally prominent.
Summer Pollution Looks Different
Pollution usually becomes a winter conversation in the national capital region. During winters, AQI often stays high. “Good” air days remain rare, while severe and hazardous conditions become common. Smog also becomes part of daily life. However, pollution does not disappear when seasons change. Instead, the dominant pollutant changes. In summer, smoke from stubble burning loses focus. Dust becomes the bigger problem.
PM10 And PM2.5 Explained
Particulate matter means tiny suspended particles in air. People can inhale these particles, which may harm health. PM10 includes particles with a diameter of 10 microns or less. That size remains smaller than a single human hair strand. PM2.5 is even smaller. Both PM10 and PM2.5 can enter the lungs. Because of its size, PM2.5 can settle deep inside the lungs.
In India, dust particles mainly create PM10 pollution. Meanwhile, fossil fuel burning, biomass burning, and vehicle emissions contribute to PM2.5 pollution.
Dust Takes Over In Summer
PM2.5 dominates winter pollution. However, PM10 takes over across north India in summer. Three factors drive this shift: dust, wind, and geography. The Thar Desert lies west and northwest of the northern plains. It covers parts of Rajasthan, Pakistan, and Afghanistan. During summer, high temperatures create a thermal low-pressure system over North India.
Prarthana Borah, Fellow at the Council on Energy, Environment and Water, said this system extends to Iran. She called it a heat low. It appears in dry, low-latitude regions when solar radiation grows intense. During daytime, land heats up and hot air rises. Consequently, a low-pressure zone forms.
Loo Carries Dust Across North India
This heat low pulls hot winds from nearby regions. These winds can reach 40-60 km per hour. People commonly call them “Loo.” However, these winds do not move empty. Loo carries dust from West Asia and the Thar Desert over north India. Then, it moves toward the Bay of Bengal.
The Indo-Gangetic Plains trap this dust. The Himalayas stand to the north. Meanwhile, the peninsular plateau lies to the south. Therefore, dust gets little space to disperse or escape. Borah explained that weather systems maintain pressure patterns during Loo episodes. As a result, western winds keep bringing dust for several days. This raises PM10 pollution levels.
Local Dust Adds More Pressure
Monsoon usually washes away this dust later. Until then, PM10 pollution keeps rising across north India. Mahesh Palawat, Vice President of Meteorology and Climate Change at Skymet Weather, explained the pattern. He said, “Summer winds in north India are westerlies, which consistently bring in dust from Thar Desert to the plains, causing PM10 to dominate summer pollution.”
Local dust sources also increase PM10 levels. Unchecked construction adds more dust to the atmosphere. Road dust rises when winds pick it up. Heat dries soil further. Then, loose soil particles enter the air. Borah said, “Hot weather desiccates the soil far more aggressively, leaving loose particles on every broken road and barren land parcel, ready to be lifted into the air.” She added that heat increases wind turbulence and helps dust travel far.
Ground-Level Ozone Adds Health Risk
Ozone contains three oxygen atoms. High in the atmosphere, ozone protects Earth from ultraviolet rays. Near the ground, however, ozone becomes a pollutant. Ground-level ozone does not directly enter air from one source. It forms through chemical reactions between nitrogen oxides and volatile organic compounds.
Vehicles, coal plants, and other industries usually release these gases. Heat and sunlight drive these reactions. Therefore, ground-level ozone becomes a bigger summer problem. Dr Gurmeet Singh Chabbra, pulmonologist at Yatharth Hospital, Faridabad, warned about its impact. He said ground-level ozone harms lung tubes and tissue. It also causes inflammation, irritation, damage, and worsens bronchial asthma.
Why Winter Dust Stays Lower
Winter in north India also brings dry conditions. Western disturbances earlier brought important rain to the plains and snow to higher areas. However, this phenomenon has reduced sharply in recent years. Still, dust does not become equally serious in winter. Dryness alone does not create dust pollution. Dust also needs energy to circulate.
Winter does not bring surface winds like summer Loo. North India also lacks a heat low during winter. Wind systems remain calmer, sometimes almost stagnant. Therefore, they cannot carry dust strongly. Moreover, winter follows monsoon, so soil keeps some moisture. Early morning dew and fog also bind soil particles. As a result, fewer particles remain suspended in air.
