NEW DELHI: Even though Delhi is considered the most polluted city in the world by WHO , it is still better off than many other Indian cities, according to recent data published by the Central Pollution Control Board (CPCB) on air pollution.The national capital stood sixth in terms of air pollution in January, with cities like Muzzaffarpur in Bihar and Varanasi showing worse air qualities.The data compares pollution levels of 24 cities on the basis of their Air Quality Index ( AQI ) with a colour code and a numerical value.According to the CPCB data, Muzzaffarpur and Varanasi are coded as 'severe' in terms of air pollution during January with an AQI value of 409 each. Delhi was 'very poor' at 362.The AQI is determined on the basis of concentration of eight pollutants, including Particulate Matter 2.5, PM 10 (fine, respirable particles), sulphur dioxide (SO2), nitrogen dioxide (NO2) carbon monoxide (CO), ozone, ammonia and lead.In December, even as Delhi had 'poor' air quality with an AQI of 293, seven other cities were ahead of it and rated as 'very poor'. These included Agra (342), Faridabad (345), Kanpur (347), Lucknow (353), Muzzaffarpur (400), Patna (373) and Varanasi (366).Similarly, in November the national capital ranked third with a score of 360, with Lucknow and Patna leading at 374 and 366 AQIs respectively.However, in September and October, Delhi was at the top of air pollution chart with 194 and 264 AQIs respectively.