Delhi records highest average carbon monoxide concentration for Jan-May period since 2022

Delhi recorded its highest average carbon monoxide concentration for the first five months of the year since 2022, with levels remaining elevated during much of the January-May period, according to data analysed by research and advisory think tank Envirocatalysts.

The data showed that the average carbon monoxide (CO) concentration between January 1 and May 31 this year stood at 1.89 milligrams per cubic metre, the highest January-May average since 2022, when it was 1.90 milligrams per cubic metre.

The corresponding averages were 1.48 milligrams per cubic metre in 2020, 1.89 milligrams per cubic metre in 2021, 1.72 milligrams per cubic metre in 2023, 1.64 milligrams per cubic metre in 2024 and 1.66 milligrams per cubic metre in 2025.

Indian standards set the permissible limit at 2 mg/NM3 (eight-hour average), while WHO guidelines place it at 4 mg/NM3 (24-hour average).

Carbon monoxide is a toxic, colourless and odourless gas that reduces the blood’s ability to carry oxygen by binding with haemoglobin. Exposure to elevated levels can lower oxygen supply to vital organs such as the heart and brain, leading to headaches, dizziness and fatigue.

Long-term or high-level exposure may increase the risk of chest pain, irregular heartbeat and other cardiovascular complications.

“High vehicle numbers and local emissions from them along with local combustion of other materials are the leading causes of high CO buildup. Higher CO levels indicate that the combustion activities are on the rise in the city which need to be curtailed, particularly the increasing private vehicle ownership making a shift towards cleaner electric-run public transportation modes,” Sunil Dahiya, founder and lead analyst at Envirocatalysts, said.

He further added that this will not just reduce the pollution but will also make the city more walkable, liveable and less congested.

Dr Rajesh Kumar Gupta, director, Respiratory Medicine and Interventional Pulmonology, Yashoda Medicity, said people exposed to high levels of carbon monoxide may develop headaches, tiredness, dizziness, trouble concentrating or a general feeling of weakness.

“Because these symptoms are common, many people may not realise that polluted air is part of the problem,” he said.

For the elderly, the risks can be even greater as many older adults already live with heart or lung conditions, Gupta said, adding that lower oxygen levels can worsen breathlessness, fatigue and heart-related problems, making everyday activities harder.