Kathmandu, March 16

Kathmandu valley, the country's capital and the largest city, has once again been ranked one of the world's most polluted city.

IQ Air, a Swiss-based air quality technology company, after gathering information from various air quality monitors in the valley, concluded that the Air Quality Index in Kathmandu a few days ago was 181, the highest in the world.

The IQ air report is based on US AQI parameter, which measures concentration of PM2.5 and PM10. Both, PM2.5 and PM10 are the smallest particulate matter often generated from vehicular emissions and other fumes and can easily be inhaled even through the mask. However, PM2.5 particulates can go deep into the lungs and into the bloodstream causing adverse health effects.

The IQ Air showed that Nepal was followed by Dhaka (167 AQI), Beijing (162 AQI), and Yangon and Lahore sharing 160 AQI each.

As per the US parameter, AQI between 0 and 50 is considered good air, 51 and 100 is moderate, 101 and 150 is unhealthy for sensitive groups, 151 and 200 is unhealthy, 201 and 300 is very unhealthy and 301 and 500 is hazardous.

Today at 9:00am, Kathmandu's AQI stood at 181 and at around 2:00pm it was 137, making the city the seventh most polluted city in the world, with Delhi topping the list. Prior to that, Kathmandu's air was unhealthy for several consecutive days. Kathmandu's average PM2.5 concentration has remained over 10 times the WHO annual air quality guideline value. Kathmandu's current PM2.5 concentration is 50 μg/m³ against the WHO's standard of 5 μg/m³. Today, the highest PM2.5 was measured at 113 μg/m³ at around 9:00am while it recorded the lowest PM2.5 at 55 μg/m³ at noon.

The mornings in the valley seem more dangerous as the PM2.5 remains mostly above 100 μg/m³. The situation in the winter season worsens as PM2.5 concentration can exceed 400 μg/m³.

Environmentalists say lack of adequate rainfall has boosted air pollution this time in Kathmandu valley. 'Kathmandu valley has not seen adequate rainfall for over six months. This has dried the air and pollutants can easily cover the air,' said environmentalist Shanker Prasad Poudel of the Department of Environment.

He further said local pollutants such as harmful gases emitted from vehicles, factories, and brick kilns were major contributing factors to air pollution here.

Similarly, burning of waste materials and agricultural fodder, and forest fires, among others are responsible for air pollution.

The valley's unique topography - bowl shaped - also traps pollutants inside the valley for longer periods, which is another factor for causing air pollution.

WHO says air pollution kills an estimated seven million people worldwide every year and every nine out of 10 people breathe air containing high levels of harmful particles.

A version of this article appears in the print on March 17, 2023, of The Himalayan Times.