A newly launched public air quality dashboard, developed by the Delhi-based research and policy organization Envirocatalysts, utilizes data from the Central Pollution Control Board (CPCB) dating back to 2015. This dashboard reveals a notable transformation in the pollution trends of the capital, where reductions in nitrogen dioxide and carbon monoxide emissions are now overshadowed by an increasing issue with ozone levels.

Introduced on Monday, the dashboard allows for an extensive, pollutant-specific analysis of emissions across different urban areas over time.

In Delhi, for example, levels of fine particulate matter (PM2.5) and coarse particles (PM10) tend to peak during winter and after the monsoon season. The period from October to February witnesses a significant rise in pollution levels, exacerbated by stagnant atmospheric conditions that keep emissions close to the surface.

Historically, January PM2.5 concentrations in Delhi have consistently exceeded safe thresholds, often surpassing 150 micrograms per cubic meter, before experiencing a drop during the monsoon months. However, this seasonal reduction does not imply a decrease in emissions. Instead, meteorological factors such as rainfall and stronger winds aid in dispersing pollutants, leading to a temporary enhancement in the air quality index (AQI).

Conversely, the data indicates that ozone levels peak in the summer, particularly in May, driven by intense sunlight that facilitates photochemical reactions between nitrogen oxides and volatile organic compounds.

Delhi’s yearly average concentration of ozone increased from 52 µg/m³ in 2021 to 66 µg/m³ in 2025, along with a significant rise in the number of ozone-dominant days, which jumped from 33 µg/m³ in 2024 to 76 µg/m³ in 2025.

Among the cities with consistent data over five years, the most substantial rises were noted in Meerut (from 53 µg/m³ to 76 µg/m³), Noida (from 54 µg/m³ to 74 µg/m³), and Muzaffarnagar (from 55 µg/m³ to 73 µg/m³), highlighting a regional trend that extends beyond Delhi.

However, these trends are not uniform. Bulandshahr in Uttar Pradesh experienced a sharp decrease in ozone levels, plummeting from 95 µg/m³ in 2021 to 45 µg/m³ in 2025, whereas Ghaziabad and Gurgaon saw moderate reductions. Bharatpur, on the other hand, remains a high-ozone area, with annual averages of 81 µg/m³ in 2023 and 84 µg/m³ in both 2024 and 2025.

Nitrogen dioxide and carbon monoxide, primarily associated with combustion sources like vehicles and industrial activities, exhibit different trends. Although these pollutants also show seasonal fluctuations, long-term data indicate a gradual decrease in their concentrations since 2015.

The long-term analysis for Delhi reveals that PM2.5 levels have reduced from approximately 117.5 µg/m³ in 2015 to 96.4 µg/m³ in 2025, while PM10 has declined from around 244 µg/m³ to 197 µg/m³ during the same timeframe. Despite these improvements, both pollutants still exceed national and global safety standards.

The ongoing presence of PM10 remains a significant concern. In recent years, coarse particulate matter has frequently dominated pollution levels, highlighting the increasing influence of dust from construction activities, road surfaces, and open land.

This past April, PM10 was the primary pollutant on over half of the monitored days—52%—across the National Capital Region (NCR).

Moreover, data indicated that Delhi’s AQI is closely linked to the broader NCR, as cities like Ghaziabad and Gurgaon continue to report elevated particulate levels.

Although Delhi experienced a year-on-year improvement, with PM2.5 levels decreasing from 77 µg/m³ in April 2025 to 68 µg/m³ in April 2026 and the number of ‘Poor’ AQI days halving from 20 to 10, neighboring cities reported deteriorating trends.

PM2.5 levels surged significantly in Hapur (from 36 µg/m³ to 67 µg/m³), Meerut (from 55 µg/m³ to 84 µg/m³), Gurgaon (from 73 µg/m³ to 92 µg/m³), Ghaziabad (from 81 µg/m³ to 99 µg/m³), and Noida (from 53 µg/m³ to 66 µg/m³).

This April, the highest PM2.5 readings were observed in Ghaziabad (99 µg/m³), Gurgaon (92 µg/m³), and Faridabad (82 µg/m³), all exceeding Delhi’s average for that month.

Sophiya Mathew serves as a correspondent for The Indian Express in New Delhi. She joined the Delhi bureau in 2024 and holds a specialization in Integrated Multimedia Journalism from the Asian College of Journalism (ACJ) in Chennai.

Her professional focus encompasses the environment and education sectors.

Mathew is recognized for her in-depth reporting on the Yamuna floodplains and the socio-economic challenges faced by the communities residing along its banks. Additionally, she investigates disparities within Delhi’s education system, which range from elite private institutions to government schools and educational services for refugees.

Recent notable articles by Mathew (December 2025) include:

• “A tale of two cities: Delhi govt schools choke in bad air, private classrooms set up air filters,” highlighting the disparity between elite schools with air filtration systems and government school students exposed to hazardous air quality.
• “Delhi sees season’s worst air day, second worst December AQI in nearly a decade,” an analysis of meteorological conditions contributing to pollution in the NCR.
• “Delhi bans non-BS VI vehicles from outside: Why curbing vehicular pollution is key,” an explanation of the rationale behind targeting specific vehicle models to reduce particulate matter.

In terms of enforcement and regulations, her coverage includes:

• “No fuel at pumps in Delhi without valid PUC certificate from December 18,” reporting on the environment ministry’s stringent “No PUC, No Fuel” policy.

For education policy, she has investigated:

• “Law to regulate school fee in Delhi risks becoming procedural, say parents,” exploring the gaps in the new Delhi School Education (Transparency in Fixation and Regulation of Fees) Bill, 2025.
• “Monsoon Session: Private school fee regulation Bill cleared after four-hour debate,” covering the legislative approval of the contentious fee hike regulation.

Mathew is known for her observational depth, often incorporating vivid details into her reporting.