The air quality in Noida remains in the 'very poor' category, although there has been a slight improvement. The AQI on Tuesday was 330 in Noida and 304 in Greater Noida. The decline in air quality can be attributed to crop burning, vehicular emissions, and industrial pollution. The situation worsened after Diwali due to the flouting of restrictions on firecrackers. The air quality is expected to remain in the 'very poor' category until Friday. Low wind speed hampers relief from the high pollution levels.