In what experts call a worrying development, carbon monoxide has been among the two primary pollutants in Delhi’s air twice over the past week. The most common primary pollutant is PM (particulate matter) 2.5. CO is harmful as it reduces the blood’s capacity to carry oxygen to organs and tissues. At R K Puram, the level of CO at 10.30 pm on Sunday was 11.60 mg/m3. At Anand Vihar, it touched 11.70 mg/m3. The one-hour standard for CO is 4 mg/m3 and the eight-hour standard is 2 mg/m3.
Dipankar Saha, head of the CPCB air quality laboratory, said: “The rise in CO concentration is very worrying as the gas is very harmful. It can even be deadly in closed rooms. The main cause of CO in air is carbons that have not been burnt completely. This can be because of unburnt fuel such as petrol, diesel, CNG, PNG or even LPG.”
According to scientists at the Delhi Pollution Control Board (DPCC), another reason for the build-up of CO in Delhi’s air is low inversion height — which is the layer beyond which pollutants cannot disperse into the upper layer of the atmosphere. This has dropped because of dipping temperatures and absence of wind.
The inversion height is lowest at night when temperatures are low. This is also when CO levels see the biggest spike. On Monday, the levels dipped below normal only in the afternoon when the temperature was in the high 20s.
“One of the biggest reasons for the spike in CO is vehicular emissions and emissions from open burning. Even engines that are not heated properly lead to CO build-up, as fuel is not completely burnt in a cold engine. This, coupled with low wind-speed, creates a situation where CO becomes one of the primary pollutants,” a senior DPCC scientist said.
The situation, however, is expected to improve in the next two days. While the wind is expected to pick up on Tuesday, Wednesday might see a light drizzle, officials at the India Meteorological Department said. Both are expected to bring down the concentration of pollutants in the air.