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Air Pollution in Kathmandu - What You Should Know

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What makes the air pollution in Kathmandu a source of concern for you is its location. The city resides in a bowl-shaped valley, and this greatly enhances the likelihood of air pollution problems. The valley's unique shape prevents the escape of industrial and vehicle fumes.

In recent decades, the air pollution in Kathmandu has worsened, due to the rapid rise in the number of inferior quality vehicles on the traffic congested roads, as well as the unregulated location of industries, particularly brick manufacturing.

So it may come as no surprise to you to learn that the Nepalese government (until now) hasn't been able to keep pace with the rapid increase in demand for building construction, road infrastructure and other types of services due to the tremendous population growth. As a consequence, there has been inadequate urban planning and this has led to pollution emitting industries being located in the middle of rapidly expanding residential suburbs.

Swift environmental action taken by the Nepalese government is now in force to reduce the presence of large existing industries that are located too close to Kathmandu. Many of these polluting industries such as cement, distilling and tanning are now being either relocated outside the city or being closed down. While these government policies have definitely curtailed the frequency of severe air pollution in Kathmandu, it has unfortunately left many people jobless.

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Severe air pollution levels during winter

Nearly every type of air pollution emitting source is operational during the dry, winter months in Kathmandu. Whereas, during the autumn, spring and summer months, all of the coal burning brick factories are closed until the next winter. So, if you do suffer from asthma, bronchitis or other pulmonary diseases, I would advise you not to travel to Kathmandu during the winter months.

In the winter months, thick fog forms over most of the Kathmandu valley during the night. This fog is caused by the drainage of cold air from the nearby mountains. This vast expanse of fog serves as a boundary separating the cleaner air above from the polluted air below.

Most of the winter air pollution in Kathmandu is a result of emissions from high volumes of road traffic, kitchen and heating fumes as well as from brick kiln emissions and other industry based sources.

Over time, this high concentration of particulate matter mixes with the fog. Under certain meteorological conditions, such as when the winds are light, this mixture of highly polluted air stagnates over Kathmandu. If there's no wind throughout the day, visibility will remain low and pollution levels will increase further.

In most instances, the thick fog/smog disperses around 11am since the wind and higher ground-level temperatures acts to break the temperature inversion which is trapping the pollution below it. Unfortunately, nearly every night in winter, this pollution event repeats itself. So, it's highly likely that you won't escape seeing the air before you breathe it in the winter in Kathmandu.

It's quite common to see people walking around the streets in the winter with air filter masks on their face during the morning rush hour in the winter.

Kathmandu's air pollution isn't as bad in the spring and autumn

city of Kathmandu

You'll be happy to learn that air pollution in Kathmandu is significantly lower in the spring and autumn compared to the winter months. The main reason for this is that the brick factories are only operational during the winter, since that's the only time it doesn't rain much.

Spring and autumn episodes of air pollution in Kathmandu, while not as severe as in winter, still can certainly cause health problems for you if you are predisposed to respiratory illnesses.

Traffic congestion is always bad near the city centre and so you can expect that the vehicle fumes will be the dominant pollution source in this region no matter what the season.

Spring time is also the lead up to the monsoon season. During this time, Kathmandu is subject to long warm sunny days with very little wind. It's during such sunny days that surface ozone levels rise significantly.

You are very unlikely to have ozone pollution when the weather is cloudy, since ozone only forms near ground-level when there's sufficient sunlight to convert the vehicle emissions to ozone.

Each day when there's ample sunlight, the ozone levels begin to rise after 9am (Nepal local time) and peak in the early afternoon between 2-3pm. After 3pm, the ozone level slowly drops. However, after sunset, since there's no sunlight, no ozone can be produced and so levels remain low until the sunrises the next day.

If you think you'll escape the pollution levels on the weekend, then unfortunately, it's a known fact that the ozone are around 10 percent higher on weekends than on weekdays.

Air pollution levels are lowest during the wet summer months

Panoramic view of Kathmandu

You'll notice that the air smells a lot cleaner during the summer and it's for good reason.

Kathmandu receives up to 80% of its total annual rainfall (1100 millimetres (43 inches)) during June, July and August. Such heavy rain washes the majority of the pollutants out of the atmosphere.

However, as soon as the rain stops, pollution levels slowly begin to rise, but because the rain is so frequent during these months, the air is simply washed clean during the next downpour of rain.

What's brick manufacturing got to do with air pollution in Kathmandu?

Brick production is one of the traditional crafts of the Nepalese people and is a valuable source of employment. Many farmers just outside Kathmandu and elsewhere in Nepal like to supplement their income when it's too dry to produce rice crops.

They grow rice during the monsoon season (summer), and then lease their land to the brick manufacturers who then place portable brick kilns on their land during the winter. The average size of these kilns is 10 acres (4 hectares).

There's approximately 125 brick kilns in operation across the Kathmandu Valley and a number of them are located in the southern and south eastern parts of Kathmandu city. These kilns are only used during the dry season (December-May) since the wet weather in other seasons prevents the bricks from setting hard.
Brick kilns use coal as their main fuel source, and this contributes to the air pollution in Kathmandu by pumping considerable quantities of sulfur dioxide (SO2) and other toxic substances into the atmosphere. Sulfur dioxide, emitted in large quantities can lead to acid rain.

These kilns produce highly concentrated amounts of fine respirable particulate matter, which interact with other industrial and vehicle fumes over Kathmandu. This combination of air pollutants is quite harmful to you if you happen to breathe in this air.

Numerous scientific studies have long shown that many people living near to brick kilns within Kathmandu suffer from asthma and other respiratory diseases more so than rest of the general Nepalese population. There's a growing body of evidence that shows that 95 deaths out of 10,000 deaths in Kathmandu Valley are due to the combination of poisonous fumes.

I should point out that these deaths are linked to people who have lived in the area all their lives and so if you are planning to stay a year or so, it's highly unlikely that this smog will cause long-term damage to your health.


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  3. Giri D, Murthy VK, Adhikary PR and Khanal SN. Estimation of number of deaths associated with exposure to excess ambient PM10 air pollution. 2007;4(2):183-188.
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  6. Yu Y, Panday A, Hodson E, Galle B and Prinn R. Monocyclic Aromatic Hydrocarbons in Kathmandu During the Winter Season. Water, air, and soil pollution 2008;191:71-81.

Do you want additional information about the air pollution in Kathmandu? Then please contact me.

Return from air pollution in Kathmandu to the air pollution facts page.

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