Delhiites would do well to avoid outdoor activities over the weekend as the city's 'very poor' air quality brings with it the possibility of respiratory illness on prolonged exposure. The average levels of PM 2.5 and PM 10 were 174 and 285 microgram per cubic metre today, a senior IMD official said and added that such conditions are expected to remain over the next two days due to atmospheric conditions. "The wind is not that strong so suspended particulate matters won't get easily dispersed. Winds from the himalayas have also brought in moisture and resulted in a drop of day- time temperature," the official said. Real-time figures of Delhi Pollution Control Committee (DPCC) were more alarming as PM 2.5 and PM 10, fine pollutants which can penetrate deep into the respiratory system, were multiple times higher than the safe limits of 60 and 100. Anand Vihar's PM 2.5 and PM 10 were 316 microgram per cubic metre and 781 at 8.50 PM while the same were 242 and 480 in the RK Puram area at 5 PM. However, the average level of pollution has seen a dip over the last two days. On December 9, 24-hour-average reading of PM 2.5 was 204 and the Central Pollution Control Board's real-time air quality index in places like Mandir Marg, Punjabi Bagh, RK Puram had touched the 'severe' category at many points during the day. 'Very poor' quality air signifies PM 10 and PM 2.5 levels between 351 and 420, and 211 to 252 micro gram per cubic metre while 'severe' is declared when PM 2.5 and PM 10 cross 253, 421 micro gram per cubic metres respectively. PM 2.5, microscopic in size, is considered by the World Health Organisation (WHO) as the best indicator of the level of health risks from air pollution.