New Delhi, Oct 31 : With air quality dipping in the national capital, there is a dramatic rise in carbon monoxide (CO) levels in some areas across the city, posing a threat to children and senior citizens. The CO levels in Delhi on Monday reached 1,491 in the city while PM 2.5 was recorded at 361, or "very poor" category as per the air quality index. With Delhi's overall air quality remaining in the "very poor" category, experts said the toxic gas can cause severe reactive airway dysfunction (RADS) even in absolutely healthy people. "CO is one of the most important and dangerous constituents of air pollution, both outdoor and indoor. Since we cannot see, smell or taste it, it keeps on damaging our respiratory system, and then to other vital organs of our body. Air purifiers cannot remove this from indoors, and high levels can immediately lead to headache, nausea, guddiness and unconsciousness," said Dr Ravi Shekhar Jha, Director & Unit Head Pulmonology, Fortis Escorts Hospital, Faridabad. The air quality in the national capital deteriorated to "very poor" category due to calm winds and cool weather conditions, weather officials said. According to data from the System of Air Quality and Weather Forecasting and Research (SAFAR), the concentration of (particulate matter) PM 10 and PM 2.5 was recorded at 302 and 361 in Delhi, respectively. The AQI was 368 in PUSA, 333 at Lodhi Road, and 370 at Mathura Road. The AQI in Noida and Gurugram stood at 378 and 347, respectively, all under the "very poor" category. An AQI between zero and 50 is considered "good", 51 and 100 "satisfactory", 101 and 200 "moderate", 201 and 300 "poor", 301 and 400 "very poor", and 401 and 500 "severe". According to the SAFAR forecast, Delhi's air quality will continue to remain under the "very poor" category for more days. "The air quality will deteriorate more in the coming days," said an expert. Dr G.C. Khilnani, Chairman - Pulmonology, Critical care & Sleep medicine, PSRI Hospital in Delhi, said that cancers of all the organs, heart disease, strokes are all caused by this menace. "Besides feeling of general ill health, headaches, low energy, sleep disturbances, reduced appetite affects our day to day life. Reducing the exposure by exercising restraint is equally important," he said. /IANS