Delhi air pollution debate often focuses on particulate matter, especially PM2.5. However a more immediate threat has been steadily rising across the city’s busiest roads: nitrogen dioxide. This harmful gas, released primarily from vehicle exhaust during rush hour, regularly exceeds recommended safety limits and is directly linked to respiratory irritation, coughing, wheezing and reduced lung function.
A recent report by the Centre for Science and Environment highlights a significant connection between traffic and daily pollution spikes. According to the findings, levels of PM2.5 tend to rise and fall in line with nitrogen dioxide during morning and evening congestion. While nitrogen dioxide levels surge immediately because of tailpipe emissions, PM2.5 builds slowly and becomes trapped close to the ground during winter, worsening air quality during the most vulnerable hours of the day.
Experts note that carbon monoxide, another dangerous pollutant associated with vehicles, is also increasing across Delhi. Together, these pollutants are making life more difficult for residents, especially for children, older adults and individuals with asthma or chronic respiratory conditions.
Pulmonologist Dr Arunesh Kumar explains that nitrogen dioxide is not only damaging on its own, it also contributes to the formation of additional PM2.5 particles in the air. Instead of debating which pollutant is more dangerous, he warns that exposure to both simultaneously significantly amplifies health risk. Long-term inhalation can result in chronic bronchitis, pneumonia and recurring lung infections. In children, prolonged exposure can slow lung development and increase the risk of asthma later in life.
Traffic congestion remains at the centre of this crisis. Slow-moving vehicles and idling engines release higher amounts of nitrogen dioxide, carbon monoxide, benzene and ultrafine particles that remain at breathing level. The impact is even more severe during winter, when pollutants remain trapped under a shallow boundary layer, creating dense and persistent smog.
While air purifiers can reduce PM2.5 indoors, they offer limited protection against harmful gases unless equipped with specialised activated carbon filters. Health experts recommend keeping windows closed during rush hour, avoiding indoor burning sources and maintaining good ventilation as temporary precautions. However, they emphasise that individual measures cannot replace a long-term solution.
Environmental researchers continue to state that reducing emissions must be the priority. Better public transport, cleaner fuels, traffic management systems and strict monitoring of vehicular pollution levels are necessary to protect public health and prevent long-term respiratory damage.
Delhi pollution crisis, once dominated by headlines about winter smog and crop burning, now reveals a quieter danger hiding in everyday traffic. With nitrogen dioxide rising alongside PM2.5, experts agree that improving the city’s air will require tackling both problems together, before the health impact becomes irreversible.