New Delhi, Oct. 18 -- Delhi's air quality index (AQI) remained in the "poor" category for a fourth consecutive day on Friday, according to the Central Pollution Control Board's (CPCB's) daily bulletin. Forecasts suggest that air quality may further deteriorate over the next few days. On Friday, the 24-hour average AQI was 254 (poor), continuing the "poor" air streak of 245 on Thursday, 233 on Wednesday and 211 on Tuesday. Data on Friday evening showed that of the 36 air quality monitoring stations for which data was available, at least six had recorded "very poor" air. The Air Quality Early Warning System for Delhi said in its bulletin, "The air quality is very likely to be in the poor category from Saturday to Sunday. The air quality is ve...