The arrival of winter has once again raised the spectre of air pollution. In response, the Delhi government on Friday announced a three-tier air treatment system at five major traffic intersections in the national capital on trial basis to deal with rising air pollution level. In a recent article, Skymet Weather Services, a private Indian company that provides weather forecast and solutions, argued: “In winters, temperatures drop quickly with winds blowing at lighter speeds. And due to the absence of major weather systems, the sky is also clear. These factors allow the Earth’s surface to cool down quickly. This leads to condensation of moisture available in the air near the Earth’s surface. The dust and smoke particles mix with the condensed layer of haze and forms smog or smoke haze. This layer or blanket of pollution is suspended in the atmosphere due to the absence of strong winds, which is the case at present.” Many areas of the national capital are under threat of a dangerous rise in air pollution. The level of ultrafine particulate matter from the atmosphere that can enter your lungs or PM 2.5 clocked 321 micrograms per cubic metre on the Air Quality Index (AQI), according to recent data collated by the System of Air Quality and Weather Forecasting and Research (SAFAR). Health experts contend that once such particulate matter enters the lungs, they restrict the availability of oxygen to lung muscles, affecting the supply of essential air flow. Apart from other serious health-related risks, the accumulation of particulate matter could ultimately result in cardiovascular and respiratory diseases and lung cancers. Matters are made worse by the burning of crop stubble in neighbouring Haryana and Punjab during the winter period. Winds from the west and north-west direction carry the smoke from this stubble burning to the national capital. Problems surrounding Delhi’s deteriorating air quality require urgent action. According to the World Health Organisation, Delhi ranks above Beijing as the world’s most polluted city. With the national capital on the cusp of Diwali, the AAP government on Tuesday ordered a crackdown on illegally imported toxic firecrackers during the festival and enforcement of Supreme Court's directions banning bursting of crackers after 10 pm. Despite a similar order last year, residents continued to blast crackers late into the night, with the national Capital enveloped in a thick blanket of smog.