The winter is a cruel period. The people, animals and plants are subjected to live in harsh climatic conditions. Cold-related ailments pester them, making their life miserable. This is natural phenomenon whose consequences can be minimised but not entirely avoided. This severity of winter is known to all ordinary people who take all necessary precautions and measures to beat it. But there is another harsh reality of winter – it also deteriorates the quality of air. Scientists have found out that as the westerly wind blows during the winter, it causes the temperature inversion process, preventing the flow of air in the atmosphere. A layer of cool air at the surface of atmosphere is covered by a layer of warmer air. This leads to the cold shade condition, which in turn hinders the strong blow of wind.

When the nature-made factors combine with that of human-made, air pollution further worsens, inviting numerous health problems. The burning of firewood, and agriculture and solid wastes, wildfires and running of brick kilns and factories generate hazardous smoke, which accumulate in certain layer of atmosphere with weak blowing of wind. The air pollution had reached dangerous level when the sky was filled with smoke and dust particles towards the end of this March, prompting the authorities to shut down the schools for four days. As there was no rain, the atmosphere was clogged with dirty gases and particles. The prolonged drought gave rise to the wildfires. The abnormal climatic condition turned Kathmandu into one of the most polluted cities in the world.

In order to keep tabs on the level of air pollution, Nepal has established 25 stations, including seven in the Kathmandu Valley to determine the air quality index (AQI), according to a news report published in this daily on Sunday. There are two minimum standards for measuring AQI in Nepal -- PM (particulate matters) 10 and PM 2.5. The standard for PM 10 is 120 micrograms per cubic metre, while it is 40 micrograms for PM 2.5. PM is tiny particles or droplets in the air that are two-and-a-half microns or less in width. Experts say that particles of PM 2.5 size are hazardous and can enter the respiratory track. They are the source of irritation of eyes, nose, throat and cause coughing and shortness of breath, among others. On Friday, Kathmandu’s AQI was measured at 147 that was unhealthy for sensitive group while Pokhara had 187 which was harmful to the people of all age groups.

Biomass burning has been considered key factor behind reduced air quality during the pre- and post-monsoon seasons. Nepal government has adopted Kathmandu Valley Air Quality Management Action Plan-2020 to contain air pollution. It has rolled out around 100 programmes that include management of household and agricultural wastes in an eco-friendly way, control of vehicle emissions, construction-related works, indoor pollution and industrial emissions. It seeks to put in place environmentally sustainable transport system but much needs to be done in this regard. It has also focused on devising appropriate policy and legal framework to boost air quality. It has become imperative to launch vigorous awareness campaign involving all stakeholders. The government needs to invest in green public transport system that does not only help cut the emissions but also benefit the commuters.