The Threat of Ambient Air Pollution in Kathmandu, Nepal


Air pollution has been a major problem of 21st century for both developed and developing world. It has a negative impact on various environmental aspects which directly or indirectly affect the quality of human health. Nepal, especially Kathmandu, in the current situation, is observing rapid urbanization and various infrastructure development projects. As a result, these sorts of human activities have been responsible for increasing air pollution in an enormous rate inside Kathmandu Valley. Chronic exposure of deteriorated air increases the chance of Noncommunicable Disease (NCD) like lung disease, heart disease, and cancers. Short term exposures also invite respiratory diseases and allergy. This review is an attempt to summarize the updated knowledge on the threat of air pollution on public health and discuss the sources of air pollutants in Kathmandu. We reviewed the literatures that were published in PMC, MEDLINE, life science journals, and organization official websites and finally came up with the findings and their interpretation that reveal the current scenario in the context of Kathmandu’s air quality status and its impact on human health. The knowledge about the invisible killer’s role in causing acute and chronic diseases may help in finding out the answer of the question regarding its effect and prevention.

1. Introduction

Kathmandu Valley, well known as city of temples, has now transformed itself into city of pollution. The city of temples is now clad in dust and smoke. The pristine blue hills and the crisp blue sky that covered the valley just about two decades ago now appear gray and hazy due to the stagnant smog that hovers over them. Kathmandu has a population density of 13,225 per km2 [1] as of data recorded by Central Bureau of Statistics in 2011, with population growth rate of 4.78% [2]. Such a high population in the valley is due to its being the capital city and people from all over the country throng to the city in pursuit of better life and opportunities. The valley is surrounded by high mountains ranging from 2000 to 2800 metres from sea level [3]. Due to this, the valley has a unique bowl-shaped topographic structure which restricts the movement of wind thereby retaining the pollutants in the air [4–6]. This makes the valley particularly vulnerable to air pollution.

World Health Organization (WHO) defines air pollution as contamination of the indoor or outdoor environment by any chemical, physical, or biological agent that modifies the natural characteristics of the atmosphere. Common sources of air pollution are household combustion devices, motor vehicles, industrial facilities, and forest fires [7]. Air pollution is a complex mixture of thousands of components, majority of which include airborne Particulate Matter (PM) and gaseous pollutants like ozone (O3), nitrogen dioxide (NO2), volatile organic compounds (like benzene), carbon monoxide (CO), sulfur dioxide (SO2), etc. [8, 9]. A variety of respiratory and other diseases, which can also be fatal, are caused by outdoor and indoor air pollution [7]. Particulate Matter (PM 10) is that suspended particle that is about 10µm in diameter and mainly arises from the poor quality roads, construction sites, and farms and is responsible for causing irritation in eyes, nose, and acute respiratory infections [10]. High rate of PM10 associated mortality and respiratory illness are found in children and adults [11]. On the other hand PM2.5 (particles less than 2.5 µm in diameter) penetrate deep into the lung, irritate and corrode the alveolar wall, consequently impair lung function [12], and even penetrate the blood [7]. It has been shown that PM2.5 is a public health concern whose exposure leads to decreased life expectancy [13–16]. The high concentration of CO forms carboxyhemoglobin (COHb) and exacerbates heart attack and also affects nervous system, NO2 causes bronchitis and bronchopneumonia, and SO2 causes eye irritation, shortness of breath, chronic bronchitis, asthma, various heart diseases, lung disease, cancer [11], and conjunctivitis [17]. O3 is associated with stimulation of transcription factors and increased expression of cytokine and adhesion molecules which lead to the development of cardiovascular and respiratory diseases [18–20]. Air pollution’s association with autoimmune diseases has been published [21, 22]. Air pollution has been emerging as a major threat to the whole ecosystem.

Geographically, Nepal is a small landlocked country sandwiched between two giant countries India and China. Though these two countries have been emerging as supreme economic powers, they still struggle in managing their environmental air quality. Studies have shown that major cities of India like Delhi, Raipur, Gwalior, and Lucknow are listed among the world’s top 10 polluted cities and altogether 37 Indian cities feature in a list of 100 most polluted cities globally, with highest PM10 [25]. Delhi the capital of India is classed as the world’s most polluted capital city with air pollution parameters 30 times higher than WHO’s recommended upper limit [26]. China a rapidly developing country equally suffers from air pollution. Rapid industrialization and high energy consumption have been the major reasons of air pollution in China. Cities such as Jingjinji, Beijing, Tianjin, and Chongjin and northwest part are the places that are highly polluted [27]. PM2.5 is considered the main pollutant of atmospheric pollution in China [28]. It was found that average PM2.5 concentration among 210 cities in China is approximately more than 8 times higher than WHO recommended level [29]. In Nepal, along with the rapid and uncontrolled urbanization and haphazard developmental projects, people are being victimized with serious airborne diseases. Though few studies and publications have been done regarding air pollution in Kathmandu, the city has now been regarded as severely polluted place [30]. This article hence emphasizes highlighting the effects, sources, status, and threats of air pollution in Kathmandu Valley.

2. Sources

A variety of factors are responsible for deteriorating the quality of air. Nepal is a rapidly urbanizing country. A data of 2014 shows 4.6 million of Nepalese live in urban areas [31]. This trend is increasing rapidly and it is estimated that urban population will reach 60 million by 2040 [32]. Subsequent increase in number of vehicles is one of the main culprits of air pollution [33, 34]. Kathmandu Valley has seen a rapid increase in vehicle numbers in the last 15 years. Data have shown that in 2000/1, number of registered vehicles was 24,003 and by 2015/16 it has increased to 7, 79,822. This shows an increment by more than 32 times in the last one and a half decade. The graph shown in Figure 1 illustrates the vehicles registered on different categories among which private vehicles like motorcycles and cars top the list, respectively. The trend of purchasing new vehicle is also seen to be increasing as the year 2015/16 sees the largest number of registered vehicles [23]. Private vehicles are increasing in comparison to public transport vehicle. Due to lack of an efficient public transport system, many residents have chosen to buy private vehicle. Emissions from vehicles are particularly toxic as diesel powered vehicles, which are considered deadly pollutant and carcinogen, are more numerous than the petrol powered ones. This fact agrees with the report of WHO where it has stated that low and middle income countries suffer superfluously from transport generated pollution due to old and inefficient diesel powered vehicles [35]. Besides vehicles, haphazard digging of road for currently ongoing Melamchi water project, brick kilns, unplanned expansion of roads, ill-managed dumping of building materials on the busy road sides, and the old engine vehicles that race incessantly on the pothole laden roads are adding insult to injury.